Sainavle

• Calorimetry And Thermal Expansion Multiple Choice Question And Answers
• Chapter 3 Centre Of Mass Multiple Choice Question And Answers
• Chapter 4 Elasticity And Viscosity Multiple Choice Question And Answers

• Chapter 5 Fluid Mechanics Multiple Choice Questions And Answers
• Chapter 6 Friction Multiple Choice Question And Answers
• Chapter 7 Gravitation Multiple Choice Question Ans Answers
• Chapter 8 Heat Transfer Multiple Choice Question And Answers
• Chapter 9 Kinetic Theory Of Gases And Thermodynamics MCQs
• Chapter 10 Mathematical Tools Multiple Choice Question And Answers

NEET Physics Class 11 Chapter 9 Kinetic Theory Of Gases And Thermodynamics Multiple Choice Question And Answers

Question 1. When an ideal gas is compressed isothermally then its pressure increases because :

1. Its potential energy decreases
2. Its kinetic energy increases and molecules move apart
3. Its number of collisions per unit area with walls of container increases
4. Molecular energy increases

Answer: 3. Its number of collisions per unit area with walls of container increases

Question 2. Which of the following quantities is zero on average for the molecules of an ideal gas in equilibrium?

1. Kinetic energy
2. Momentum
3. Density
4. Speed

Answer: 2. Momentum

Question 3. The average momentum of a molecule in a sample of an ideal gas depends on

1. Temperature
2. Number of moles
3. Volume
4. None of these
5. Answer: 4. None of these

Kinetic Theory of Gases and Thermodynamics NEET Class 11 MCQs

Question 4. The volume of air increases by 5% in its adiabatic expansion. The percentage decrease in its pressure will be –

1. 6%
2. 7%
3. 8%

Answer: 3. 7%

Question 5. The equation for an ideal gas is :

1. PV = RT
2. PV^γ = constant
3. C_p– C_V= R
4. None of these

Answer: 1. PV = RT

Question 6. The temperature and pressure of 2g oxygen are 27° C and 76 cm Hg, then the volume of the gas is:

1. 1.53 litre
2. 2.44 litre
3. 3.08 litre
4. 44.2 litre

Answer: 1. 1.53 liter

Question 7. Significance of a and b in van der Waal’s equation :

1. A and b both show the correction in the volume of gas
2. A and b both show cohesive force between molecules
3. A shows cohesive force while b shows correction in volume
4. A shows correction in volume while b shows cohesive force

Answer: 3. A shows cohesive force while b shows correction in volume

Question 8. In which condition a real gas behaves as an ideal gas?

1. At high pressure
2. At low pressure
3. At low temperature
4. All the above

Answer: 2. At low pressure

Question 9. Which of the following parameters does not characterize the thermodynamic state of matter?

1. Temperature
2. Pressure
3. Work
4. Volume

Answer: 3. Work

Question 10. 1 calorie is the heat required to increase the temperature of 1 gm of water by 1°C from

1. 13.5°C to 14.5°C at 76 mm of Hg
2. 14.5 °C to 15.5°C at 760 mm of Hg
3. 6.5 °C to 7.5°C at 76 mm of Hg
4. 98.5 °C to 99.5°C at 760 mm of Hg

Answer: 2. 14.5 °C to 15.5°C at 760 mm of Hg

Question 11. A real gas behaves like an ideal gas if its

1. Pressure and temperature are both high
2. Pressure and temperature are both low
3. Pressure is high and temperature is low
4. Pressure is low and temperature is high

Answer: 4. Pressure is low and temperature is high

Question 12. Two non-reactive monoatomic ideal gases have their atomic masses in the ratio 2 : 3. The ratio of their partial pressures, when enclosed in a vessel kept at a constant temperature, is 4 : 3. The ratio of their densities is:

1. 1: 4
2. 1: 2
3. 6: 9
4. 8: 9

Answer: 4. 8: 9

Question 13. The degrees of freedom of a stationary rigid body about its axis will be :

1. One
2. Two
3. Three
4. Four

Answer: 3. Three

Question 14. The temperature of an ideal gas at atmospheric pressure is 300 K and the volume is 1 m³. If temperature and volume become double, then the pressure will be :

1. 10⁵ N/m²
2. 2 × 10⁵ N/m²
3. 0.5 × 10⁵ N/m²
4. 4 × 10⁵ N/m²

Answer: 1. 105 N/m²

Question 15. If 2g of helium is enclosed in a vessel at NTP, how much heat should be added to it to double the pressure? (Specific heat of helium = 3 J/gm K)

1. 1638 J
2. 1019 J
3. 1568 J
4. 836 J

Answer: 1. 1638 J

Question 16. At what temperature volume of an ideal gas at 0ºC become triple?

1. 546ºC
2. 182ºC
3. 819ºC
4. 646ºC

Answer: 1. 546ºC

Question 17. Two balloons are filled, one with pure He gas and the other with air, respectively. If the pressure and temperature of these balloons are the same, then the number of molecules per unit volume is

1. More in the He filled balloon
2. Same in both balloons
3. More in an air-filled balloon
4. In the ratio of 1: 4

Answer: 2. Same in both balloons

Question 18. A diatomic molecule has

1. 1 degree of freedom
2. 3 degrees of freedom
3. 5 degrees of freedom
4. 6 degrees of freedom

Answer: 3. 5 degrees of freedom

Question 19. The equation of state for 5g of oxygen at a pressure P and temperature T, when occupying a volume V, will be :

1. PV = (5/32) RT
2. PV = 5RT
3. PV = (5/2) RT
4. PV = (5/16) RT

Answer: 1. PV = (5/32) RT

Question 20. Two thermally insulated vessels 1 and 2 are filled with air at temperature (T₁, T₂), volume (V₁, V₂), and pressure (P₁, P₂) respectively. If the valve joining the two vessels is opened, the temperature inside the vessel at equilibrium will be:

1. \(T_1+T_2\)
2. \(\left(\mathrm{T}_1+\mathrm{T}_2\right) / 2\)
3. \(\frac{T_1 T_2\left(P_1 V_1+P_2 V_2\right)}{P_1 V_1 T_2+P_2 V_2 T_1}\)
4. \(\frac{T_1 T_2\left(P_1 V_1+P_2 V_2\right)}{P_1 V_1 T_1+P_2 V_2 T_2}\)

Answer: 3. \(\frac{T_1 T_2\left(P_1 V_1+P_2 V_2\right)}{P_1 V_1 T_2+P_2 V_2 T_1}\)

Question 21. A gas behaves more closely as an ideal gas at

1. Low pressure and low temperature
2. Low pressure and high temperature
3. High pressure and low temperature
4. High pressure and high temperature

Answer: 2. Low pressure and high temperature

Question 22. The figure shows graphs of pressure vs density for an ideal gas at two temperatures T₁ and T₂.

1. T₁> T₂
2. T₁= T₂
3. T₁< T₂
4. Any of the three is possible

Answer: 1. T₁> T₂

Question 23. Suppose a container is evacuated to leave just one molecule of gas in it. Let ν_a and ν_rms represent the average speed and the rms speed of the gas.

1. ν_a> ν_rms
2. ν_a< ν_rms
3. ν_a= ν_rms
4. νrms is undefined

Answer: 3. ν_a= ν_rms

Question 24. The rms speed of oxygen molecules in a gas is ν. If the temperature is doubled and the O₂ molecule dissociates into oxygen atoms, the rms speed will become

1. ν
2. ν √2
3. 2ν
4. 4ν

Answer: 3. 2ν

Question 25. Consider a mixture of oxygen and hydrogen kept at room temperature. Compared to a hydrogen molecule an oxygen molecule hits the wall

1. With a greater average speed
2. With a smaller average speed
3. With greater average kinetic energy
4. With smaller average kinetic energy.

Answer: 2. With a smaller average speed

Question 26. Consider the quantity MkT / pV of an ideal gas where M is the mass of the gas. It depends on the

1. Temperature of the gas
2. The volume of the gas
3. The pressure of the gas
4. Nature of the gas

Answer: 4. Nature of the gas

Question 27. If the volume of a gas is decreased by 10% during the isothermal process then its pressure will be –

1. Decrease by 10%
2. Increase by 10%
3. Decrease by 11.11%
4. Increase by 11.11%

Answer: 4. Increase by 11.11%

Question 28. The gases carbon-monoxide (CO) and nitrogen at the same temperature have kinetic energies E₁ and E₂ respectively. Then :

1. E₁= E₂
2. E₁> E₂
3. E₁< E₂
4. E₁ and E₂ cannot be compared

Answer: 1. E₁= E₂

Question 29. In equilibrium, the velocity of molecules of a gas depends on its temperature as

1. \(\mathrm{u} \propto \mathrm{T}\)
2. \(\mathrm{u} \propto \frac{1}{\mathrm{~T}}\)
3. \(\mathrm{u} \propto \sqrt{\mathrm{T}}\)
4. \(\mathrm{u} \propto \mathrm{T}^0\)

Answer: 3. \(\mathrm{u} \propto \sqrt{\mathrm{T}}\)

Question 30. A mixture of 2 moles of helium gas (atomic mass = 4 amu) and 1 mole of argon gas (atomic mass = 40 amu) is kept at 300 K in a container. The ratio of the rms speeds \(\left(\frac{v_{\mathrm{rms}}(\text { helium })}{v_{\mathrm{rms}}(\text { argon })}\right)\) is:

1. 0.32
2. 0.45
3. 2.24
4. 3.16

Answer: 4. 3.16

Question 31. The ratio of the average kinetic energy of H₂ and O₂ at a given temperature is :

1. 1: 16
2. 1: 8
3. 1: 4
4. 1: 1

Answer: 4. 1: 1

Question 32. If the temperature of the gas is increased to three times, then its root mean square velocity becomes:

1. 3 times
2. 9 times
3. 12times
4. 3times

Answer: 4. 3times

Question 33. Which of the following statements is incorrect according to assumptions of the kinetic theory of gases?

1. The potential energy of a molecule is zero
2. Molecules move randomly in all directions
3. the kinetic energy of molecules changes when they collide with the wall of a container
4. None of these

Answer: 4. None of these

Question 34. At what temperature is the rms velocity of a hydrogen molecule equal to that of an oxygen molecule at 47º C?

1. 80 K
2. –73 K
3. 3 K
4. 20 K

Answer: 4. 20 K

Question 35. The kinetic energy of one mole gas at 300 K temperature, is E. At 400 K temperature kinetic energy is E’.The value of E’/E is :

1. 1.33
2. \(\sqrt{\left(\frac{4}{3}\right)}\)
3. \(\frac{16}{9}\)
4. 2

Answer: 1. 1.33

Question 36. If the temperature becomes triple, the root mean square velocity of gas molecules will be :

1. \(\text { v } \sqrt{2}\)
2. \(\text { v/ } \sqrt{3}\)
3. \(\sqrt{3} v\)
4. Same

Answer: 3. \(\sqrt{3} v\)

[υ is the root mean square velocity of gas molecules at temperature T]

Question 37. On increasing the temperature of gas contained in a closed vessel by 1°C, the pressure increases by 0.4%. The initial temperature of a gas is:

1. 25 K
2. 250 K
3. 2500° K
4. 250° C

Answer: 2. 250 K

Question 38. When the temperature of a gas is increased then which of the following statements is always true?

1. Work is done on the gas
2. Heat is supplied to a gas
3. The internal energy of the gas is increased
4. The pressure of gas remains unchanged.

Answer: 3. Internal energy of a gas is increased

Question 39. The speed of sound through oxygen at TK is v ms^-1. As the temperature becomes 2T and oxygen gas dissociates into atomic oxygen, the speed of sound :

1. Remains the same
2. Becomes 2v
3. Becomes \(\sqrt{2 v}\)
4. None of these

Answer: 4. None of these

NEET Physics Chapter 9 Kinetic Theory of Gases and Thermodynamics Multiple Choice Questions

Question 40. When the temperature of an ideal gas is increased from 27ºC to 227ºC, its rms speed is changed from 400 m/s to v_s. The v_s is :

1. 516 m/s
2. 450 m/s
3. 310 m/s
4. 746 m/s

Answer: 1. 516 m/s

Question 41. The root mean square and most probable speed of the molecules in a gas are

1. Same
2. Different
3. Cannot say
4. Depends on the nature of the gas

Answer: 2. Different

Question 42. Hydrogen gas is filled in a container of volume 20 liter. The average translational kinetic energy of all its molecules is 1.5 × 10⁵ J. Pressure of hydrogen in the cylinder is:

1. 2 × 10⁶ N/m²
2. 3 × 10⁶ N/m²
3. 4 × 10⁶ N/m²
4. 5 × 10⁶ N/m²

Answer: 4. 5 × 10⁶ N/m²

Question 43. The root mean square speed of ideal hydrogen gas in a closed chamber at 0°C is 3180 m/s. Its pressure will be (density of hydrogen gas is 8.99 × 10^-2 kg/m³, 1 atm. = 1.01 × 10⁵ N/m²)

1. 1.0 atm.
2. 1.5 atm.
3. 2.0 atm.
4. 3.0 atm.

Answer: 4. 3.0 atm.

Question 44. A flask contains argon and chlorine in the ratio 3: 1 by mass. The temperature of the mixture is 300 K. If the atomic mass of argon = 39.9 u, and the molecular mass of chlorine = 70.9u, then the ratio of average kinetic energy per molecule of argon to chlorine gas is

1. 1: 1
2. 3: 1
3. 1 : 3
4. 39.9: 70.9

Answer: 1. 1: 1

Question 45. At the same temperature and pressure, the densities of two diatomic gases are d₁ and d₂, The ratio of velocities of sound in these gases will be

1. \(\frac{d_1}{d_2}\)
2. \(\sqrt{\frac{d_2}{d_1}}\)
3. \(\sqrt{\frac{d_1}{d_2}}\)
4. \(\frac{d_2^2}{d_1^2}\)

Answer: 2. \(\sqrt{\frac{d_2}{d_1}}\)

Question 46. The ratio of the mean speed of hydrogen molecules to the mean speed of nitrogen molecules in a sample containing a mixture of the two gases.

1. \(\sqrt{14}\)
2. \(\sqrt{7}\)
3. \(\sqrt{28}\)
4. None of these

Answer: 1. \(\sqrt{14}\)

Question 47. Three closed vessels A, B, and C are at the same temperature T, and contain gases that obey the Maxwellian distribution of velocities. Vessel A contains only O₂, B only N_2, and C a mixture of equal quantities of O₂ and N₂. If the average speed of O₂ molecules in vessel A is V₁, that of the N₂ molecules in vessel B is V₂, the average speed of the O₂ molecules in vessel C will be :

1. (V₁+ V₂)/2
2. V₁
3. (V₁V₂)1/2
4. \(\sqrt{3 \mathrm{kT} / \mathrm{M}}\)

Answer: 2. V₁

Question 48. The pressure of an ideal gas is written as P = \(\frac{2 E}{3 V}\). Here E refers to

1. Translational kinetic energy
2. Rotational kinetic energy
3. Vibrational kinetic energy
4. Total kinetic energy.

Answer: 1. Translational kinetic energy

Question 49. Which of the following quantities is the same for all ideal gases at the same temperature?

1. The kinetic energy of 1 mole
2. The kinetic energy of 1 g
3. The number of molecules in 1 mole
4. The number of molecules in 1 g

Answer: 3. The number of molecules in 1 mole

Question 50. Let ΔU₁ and ΔU₂ be the changes in internal energy of the system in the processes A and B then

1. ΔU₁> ΔU₂
2. ΔU₁= ΔU₂
3. ΔU₁< ΔU₂
4. ΔU₁≠ ΔU₂

Answer: 2. ΔU1= ΔU₂

Question 51. The internal energy of a mono-atomic gas is –

1. \(\frac{5 R T}{2}\)
2. \(\frac{3 R T}{2}\)
3. \(\frac{5 R T}{3}\)
4. \(\frac{7 R T}{3}\)

Answer: 2. \(\frac{3 R T}{2}\)

Question 52. The change in internal energy, when a gas is cooled from 927ºC to 27ºC is

1. 100%
2. 200%
3. 75%
4. 400%

Answer: 3. 75%

Question 53. A gas mixture consists of 2 moles of oxygen and 4 moles of argon at temperature T. Neglecting all vibrational modes the total internal energy of the system is:

1. 4RT
2. 15RT
3. 9RT
4. 11RT

Answer: 4. 11RT

Question 54. An ideal gas is filled in a closed rigid and thermally insulated container. A coil of 100Ω resistor carrying current 1A for 5 minutes supplies heat to the gas. The change in internal energy of the gas is

1. 10 KJ
2. 20 KJ
3. 30 KJ
4. 0 KJ

Answer: 3. 30 KJ

Question 55. 300 calories of heat is supplied to raise the temperature of 50 gm of air from 20°C to 30°C without any change in its volume. Change in internal energy per gram of air is

1. Zero
2. 0.6 calories
3. 1.2 calories
4. 6.0 calories

Answer: 4. 6.0 calories

Question 56. Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside will:

1. Increase
2. Decrease
3. Remain same
4. Decrease for some, while increase for others

Answer: 3. Remain same

Question 57. According to the law of equal distribution of energy, the mean energy of a molecule per degree of freedom is:

1. \(\frac{1}{2} \mathrm{KT}\)
2. KT
3. \(\frac{3}{2} \mathrm{KT}\)
4. \(\frac{5}{2} \mathrm{KT}\)

Answer: 1. \(\frac{1}{2} \mathrm{KT}\)

Question 58. Which of the following statements is correct for any thermodynamic system?

1. The internal energy changes in all processes
2. Internal energy and entropy are state functions
3. The change in entropy can never be zero
4. The work done in an adiabatic process is always zero

Answer: 2. Internal energy and entropy are state functions

Question 59. A system goes from A to B via two processes 1 and 2 as shown in the figure. If ΔU₁ and ΔU₂ are the changes in internal energies in processes 1 and 2 respectively, then:

1. ΔU₁= ΔU₂
2. The relation between ΔU₁ and ΔU₂ cannot be determined
3. ΔU₂> ΔU₁
4. ΔU₂< ΔU₁

Answer: 1. ΔU₁= ΔU₂

Question 60. Two rigid boxes containing different ideal gases are placed on a table. Box A contains one mole of nitrogen at temperature To, while box B contains one mole of helium at temperature (7/3)To. The boxes are then put into thermal contact with each other, and heat flows between them until the gases reach a common final temperature. (Ignore the heat capacity of boxes). Then, the final temperature of the gases, Tfin terms of T₀ is :

1. \(\mathrm{T}_{\mathrm{f}}=\frac{3}{7} \mathrm{~T}_0\)
2. \(\mathrm{T}_{\mathrm{f}}=\frac{7}{3} \mathrm{~T}_0\)
3. \(T_f=\frac{3}{2} T_0\)
4. \(\mathrm{T}_{\mathrm{f}}=\frac{5}{2} \mathrm{~T}_0\)

Answer: 3. \(T_f=\frac{3}{2} T_0\)

Question 61. An insulated container of gas has two chambers separated by an insulating partition. One of the chambers has volume V₁ and contains ideal gas at pressure p₁ and temperature T₁. The other chamber has volume V₂ and contains ideal gas at pressure p₂ and temperature T₂. If the partition is removed without doing any work on the gas, the final equilibrium temperature of the gas in the container will be –

1. \(\frac{T_1 T_2\left(p_1 V_1+p_2 V_2\right)}{p_1 V_1 T_2+p_2 V_2 T_1}\)
2. \(\frac{p_1 V_1 T_1+p_2 V_2 T_2}{p_1 V_1+p_2 V_2}\)
3. \(\frac{p_1 V_1 T_2+p_2 V_2 T_1}{p_1 V_1+p_2 V_2}\)
4. \(\frac{T_1 T_2\left(p_1 V_1+p_2 V_2\right)}{p_1 V_1 T_1+p_2 V_2 T_2}\)

Answer: 1. \(\frac{T_1 T_2\left(p_1 V_1+p_2 V_2\right)}{p_1 V_1 T_2+p_2 V_2 T_1}\)

Question 62. In the following figures to (4), variation of volume by change of pressure is shown. A gas is taken along the path ABCDA. The change in internal energy of the gas will be:

1. Positive in all cases from(1) to (4)
2. Positive in case (1), and but zero in case(4)
3. Negative in cases (1), and but zero in case
4. Zero in all the four cases.

Answer: 4. Zero in all the four cases.

Question 63. An ideal gas changes from state a to state b as shown in Fig. What is the work done by the gas in the process?

1. Zero
2. Positive
3. Negative
4. Infinite

Answer: 1. Zero

Question 64. The process ΔU = 0, for an ideal gas, can be best represented in the form of a graph:

Answer: 2

Question 65. In the following V-T diagram what is the relation between P₁ and P₂:

1. P₂= P₁
2. P₂> P₁
3. P₂< P₁
4. Cannot be predicted

Answer: 3. P₂< P₁

Question 66. In the isothermal expansion of an ideal gas. Select the wrong statement:

1. There is no change in the temperature of the gas
2. There is no change in the internal energy of the gas
3. The work done by the gas is equal to the heat supplied to the gas
4. The work done by the gas is equal to the change in its internal energy

Answer: 4. The work done by the gas is equal to the change in its internal energy

Question 67. In the cyclic process shown on the P – V diagram, the magnitude of the work done is:

1. \(\pi\left(\frac{P_2-P_1}{2}\right)^2\)
2. \(\pi\left(\frac{V_2-V_1}{2}\right)^2\)
3. \(\frac{\pi}{4}\left(P_2-P_1\right)\left(V_2-V_1\right)\)
4. \(\pi\left(P_2 V_2-P_1 V_1\right)\)

Answer: 3. \(\frac{\pi}{4}\left(P_2-P_1\right)\left(V_2-V_1\right)\)

Question 68. A fixed mass of ideal gas undergoes changes in pressure and volume starting at L, as shown in Figure.

Which of the following is correct :

Answer: 2

Question 69. A fixed mass of gas undergoes the cycle of changes represented by PQRSP as shown in Figure. In some of the changes, work is done on the gas, and in others, work is done by the gas. In which pair of the changes work is done on the gas?

1. PQ and RS
2. PQ and QR
3. OR and RS
4. RS and SP.

Answer: 4. RS and SP

Question 70. Consider two processes on a system as shown in Figure. The volumes in the initial states are the same in the two processes and the volumes in the final states are also the same. Let ΔW₁ and ΔW₂ be the work done by the system in the processes A and B respectively.

1. ΔW₁> ΔW₂
2. ΔW₁= ΔW₂
3. ΔW₁< ΔW₂
4. Nothing can be said about the relation between ΔW1 and ΔW₂

Answer: 3. ΔW₁< ΔW₂

Question 71. A mass of an ideal gas undergoes a reversible isothermal compression. Its molecules will then be compared with an initial state, the same

1. Root mean square velocity
2. Mean momentum
3. Mean kinetic energy

1. (1), (2), (3) correct
2. (1), (2) correct
3. (2), (3) correct
4. (1) correct

Answer: 1. (1), (2), (3) correct

Question 72. Find work done by the gas in the process shown in the figure:

1. \(\frac{5}{2} \pi{atm} \mathrm{L}\)
2. \(\frac{5}{2} \mathrm{~atm} \mathrm{~L}\)
3. \(-\frac{3}{2} \pi {atm} \mathrm{L}\)
4. \(-\frac{5}{4} \pi \mathrm{atm} \mathrm{L}\)

Answer: 4. \(-\frac{5}{4} \pi \mathrm{atm} \mathrm{L}\)

Question 73. The change in internal energy of two moles of a gas during adiabatic expansion is found to be –100 joule. The work done during the process is –

1. 100 joule
2. –100 joule
3. Zero
4. 200 joule

Answer: 1. 100 joule

Question 74. The work done in the following figure is –

1. 2 × 10⁵joule
2. 10⁵joule
3. Zero
4. 3 × 10⁵joule

Answer: 2. 105joule

Question 75. The net amount of the work done in the following indicator diagram is –

1. Zero
2. Positive
3. Negative
4. Infinite

Answer: 1. Zero

Question 76. An ideal gas is taken via paths AB, BC, and CA as shown in Fig. The net work done in the whole cycle is-

1. 3P₁V₁
2. –3P₁V₁
3. 6P₁V₁
4. 12P₁V₁

Answer: 2. –3P₁V₁

Question 77. In the indicator diagram shown, the work done along path AB is-

1. Zero
2. 20 joule
3. –20 joule
4. 60 joule

Answer: 2. 20 joule

Question 78. In the above problem work done along path BC is –

1. Zero
2. 40 joule
3. 60 joule
4. None

Answer: 1. Zero

Question 79. In the above problem, the work done along path CA is –

1. 20 joule
2. 30 joule
3. – 30 joule
4. Zero

Answer: 3. –30 joule

Question 80. Starting the same initial conditions, an ideal gas expands from volume V₁ to V₂ in three different ways. The work done by the gas is W₁ if the process is purely isothermal, W₂ if purely isobaric, and W₃ if purely adiabatic. Then:

1. W₂> W₁> W₃
2. W₂> W₃> W₁
3. W₁> W₂> W₃
4. W₁> W₃> W₂

Answer: 1. W₂> W₁> W₃

Question 81. An ideal gas is taken through the cycle A → B → C → A as shown in Fig. If the net heat supplied to the gas in the cycle is 5 J, the work done by the gas in the process C → A is:

1. – 5 J
2. – 10 J
3. – 15 J
4. – 20 J

Answer: 1. – 5 J

Question 82. The work done by a gas taken through the closed process ABCA, see figure is

1. 6P₀V₀
2. 4P₀V₀
3. P₀V₀
4. Zero

Answer: 1. 6P₀V₀

Question 83. A system is given 400 calories of heat and 1000 joule of work is done by the system, then the change in internal energy of the system will be –

1. 680 joule
2. 680 erg
3. 860 joule
4. – 860 joule

Answer: 1. 680 joule

Question 84. If AB and CD are isothermals and AD and BC are adiabatic then the temperatures of

1. B and C are the same
2. A and C are the same
3. B and D are the same
4. The temperature of A is more than that of D

Answer: 4. Temperature of A is more than that of D

Question 85. An ideal gas initially at a state (P₁, V₁) is allowed to expand isothermally to a state (P₂, V₂). Then the gas is compressed adiabatically to its initial volume V₁. Let the final pressure be P₃ and the work done by the gas during the whole process be W, then

1. P₃> P₁ and W < 0
2. P₃> P₁ and W > 0
3. P₃< P₁ and W > 0
4. P₃< P₁ and W < 0

Answer: 1. P₃> P₁ and W < 0

Question 86. An ideal gas is taken through the process shown in the figure:

1. In process AB, work done by the system is positive
2. In process AB, heat is rejected out of the system.
3. In process AB, internal energy increases
4. In process AB internal energy decreases and in process BC internal energy increases.

Answer: 2. In process AB, heat is rejected out of the system.

Question 87. If heat is supplied to an ideal gas in an isothermal process,

1. The internal energy of the gas will increase
2. The gas will do positive work
3. The gas will do negative work
4. The said process is not possible

Answer: 2. The gas will do positive work

Thermodynamics and Kinetic Theory of Gases MCQs for NEET Physics Class 11

Question 88. A system can be taken from the initial state p₁, V₁ to the final state p₂, V₂ by two different methods. Let ΔQ and ΔW represent the heat given to the system and the work done by the system. Which of the following must be the same in both methods?

1. ΔQ
2. ΔW
3. ΔQ + ΔW
4. ΔQ – ΔW

Answer: 4. ΔQ – ΔW

Question 89. In changing the state of a system from state A to state B adiabatically the work done on the system is 322 joule. If 100 calories of heat are given to the system in bringing it from state B to state A, then the work done on the system in this process will be –

1. 98 joule
2. 38.2 joule
3. 15.9 calorie
4. 15.9 joule

Answer: 1. 98 joule

Question 90. An ideal gas heat engine operates in a Carnot cycle between 227ºC and 127ºC. It absorbs 6 kcal at a higher temperature. The amount of heat (in kcal) converted into work is equal to:

1. 1.6
2. 1.2
3. 4.8
4. 3.5

Answer: 2. 1.2

Question 91. In a closed container of 44.8 liter, the volume of monoatomic gas is filled up. The heat required to raise the temperature by 10°C will be :

1. R
2. 10R
3. 20R
4. 30R

Answer: 4. 30R

Question 92. Two moles of an ideal gas are taken in a cyclic process abcda. During the process, ab and cd temperatures are 500 K and 300 K respectively. Calculate heat absorbed by the system (In 2 = 0.69 and R = 8.3 J/mol-K)

Answer: 2290.3j

Question 93. If Q, E, and W denote respectively the heat added, change in internal energy, and the work done in a closed cycle process, then

1. W = 0
2. Q = W = 0
3. E = 0
4. Q = 0

Answer: 3. E = 0

Question 94. Which of the following is incorrect regarding the first law of thermodynamics?

1. It does not apply to any cycle process
2. It is a restatement of the principle of conservation of energy
3. It introduces the concept of the internal energy
4. It introduces the concept of the entropy

Answer: (1,4)

Question 95. When a system is taken from state I to state f along the path, it is found that Q = 50 cal and W = 20 cal. Along the path ibf Q = 36 cal. W along the path ibf is:

1. 6 cal
2. 16 cal
3. 66 cal
4. 14 cal

Answer: 1. 6 cal

Question 96. When an ideal diatomic gas is heated at constant pressure, the fraction of the heat energy supplied which increases the internal energy of the gas is.

1. \(\frac{2}{5}\)
2. \(\frac{3}{5}\)
3. \(\frac{3}{7}\)
4. \(\frac{5}{7}\)

Answer: 4. \(\frac{5}{7}\)

Question 97. Boiling water is changing into steam. Under this condition, the specific heat of water is

1. Zero
2. One
3. Infinite
4. Less than one

Answer: 3. Infinite

Question 98. Supposing the distance between the atoms of a diatomic gas to be constant, its specific heat at constant volume per mole (gram mole) is

1. \(\frac{5}{2} R\)
2. \(\frac{3}{2} R\)
3. R
4. \(\frac{7}{2} R\)

Answer: 1. \(\frac{5}{2} R\)

Question 99. A gas is formed of molecules each molecule possessing f degrees of freedom, then the value of γ = \(\frac{C_p}{C_V}\)is equal to:

1. \(\frac{2}{\mathrm{f}}\)
2. \(1+\frac{2}{f}\)
3. \(1+\frac{f}{2}\)
4. \(\mathrm{f}+\frac{1}{2}\)

Answer: 2. \(1+\frac{2}{f}\)

Question 100. During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio C_p/C_V for the gas is:

1. 4/3
2. 2
3. 5/3
4. 3/2

Answer: 4. 3/2

Question 101. Some students find values of C_V and C_P for gas in calorie/gm–mol K. Which pair is most correct?

1. C_V= 3, C_P= 5
2. C_V= 4, C_P= 6
3. C_V= 3, C_P= 2
4. C_V= 3, C_P= 4.2

Answer: 1. C_V= 3, CP= 5

Question 102. The thermal capacity of anybody is:

1. A measure of its capacity to absorb heat
2. A measure of its capacity to provide heat
3. The quantity of heat required to raise its temperature by a unit degree
4. The quantity of heat required to raise the temperature of a unit mass of the body by a unit degree

Answer: 3. The quantity of heat required to raise its temperature by a unit degree

Question 103. 1 mole of a gas with γ = 7/5 is mixed with 1 mole of a gas with γ = 5/3, then the value of γ for the resulting mixture is:

1. 7/5
2. 2/5
3. 24/16
4. 12/7

Answer: 3. 24/16

Question 104. The molar heat capacity at a constant volume of oxygen gas at STP is nearly 2.5 R. As the temperature is increased, it gradually increases and approaches 3.5 R. The most appropriate reason for this behavior is that at high temperatures

1. Oxygen does not behave as an ideal gas
2. Oxygen molecules dissociate in atoms
3. The molecules collide more frequently
4. Molecular vibration gradually becomes effective

Answer: 3. The molecules collide more frequently

Question 105. The amount of heat required to raise the temperature of 100 gm water from 20ºC to 40ºC will be –

1. 100 calorie
2. 2000 calorie
3. 4000 calorie
4. Zero

Answer: 2. 2000 calorie

Question 106. Two moles of ideal helium gas are in a rubber balloon at 30° C. The balloon is fully expandable and can be assumed to require no energy in its expansion. The temperature of the gas in the balloon is slowly changed to 35°C. The amount of heat required in raising the temperature is nearly (take R = 8.31 J/mol.K)

1. 62J
2. 104 J
3. 124 J
4. 208 J

Answer: 4. 208 J

Question 107. The molar specific heat at constant pressure of an ideal gas is \(\left(\frac{7}{2}\right)\) R. The ratio of specific heat at constant pressure to that at constant volume is:

1. \(\frac{7}{5}\)
2. \(\frac{8}{7}\)
3. \(\frac{5}{7}\)
4. \(\frac{9}{7}\)

Answer: 1. \(\frac{7}{5}\)

Question 108. One mole of ideal monoatomic gas (γ = 5/3) is mixed with one mole of diatomic gas (γ = 7/5). What is γ for the mixture? γ denotes the ratio of specific heat at constant pressure, to that at constant volume.

1. 3/2
2. 23/15
3. 35/23
4. 4/3

Answer: 1. 3/2

Question 109. A gaseous mixture consists of 16 g of helium and 16 g of oxygen. The ratio
Cof the mixture is:

1. 1.59
2. 1.62
3. 1.4
4. 1.54

Answer: 2. 1.62

Question 110. If C_P and CV denote the specific heats of nitrogen per unit mass at constant pressure and constant volume respectively, then

1. C_P – C_V = R / 28
2. C_P – C_V = R / 14
3. C_P – C_V = R
4. C_P – C_V = 28R

Answer: 1. C_P – C_V = R/28

Question 111. A gas is contained in a metallic cylinder fitted with a piston. The piston is suddenly moved in to compress the gas and is maintained at this position. As time passes, after this pressure of the gas in the cylinder

1. Increases
2. Decreases
3. Remains constant
4. Increases or decreases depending on the nature of the gas.

Answer: 2. Decreases

Question 112. Two samples A and B are initially kept in the same state. Sample A is expanded through an adiabatic process and sample B through an isothermal process upto the same final volume. The final pressures in A and B are p_A and p_B respectively.

1. p_A> p_B
2. p_A= p_B
3. p_A< p_B
4. The relation between p_A and p_B cannot be deduced.

Answer: 3. p_A< p_B

Question 113. Let T_a and T_b be the final temperature of the samples A and B respectively in the previous question then:

1. T_a< T_b
2. T_a= T_b
3. T_a> T_b
4. The relation between T_a and T_b cannot be deduced.

Answer: 1. T_a< T_b

Question 114. Let ΔW_a and ΔW_b be the work done by the systems A and B respectively in the previous question then:

1. ΔW_a> ΔW_b
2. ΔW_a= ΔW_b
3. ΔW_a< ΔW_b
4. The relation between W_a and W_b cannot be deduced

Answer: 3. ΔW_a< ΔW_b

Question 115. Four curves A, B, C, and D are drawn in Figure. for a given amount of gas. The curves that represent adiabatic and isothermal changes are

1. C and D respectively
2. D and C respectively
3. A and B respectively
4. B and A respectively

Answer: 3. A and B respectively

Question 116. For an ideal gas, the heat capacity at constant pressure is larger than that at constant volume because

1. Positive work is done during the expansion of the gas by the external pressure
2. Positive work is done during expansion by the gas against external pressure
3. Positive work is done during expansion by the gas against intermolecular forces of attraction
4. More collisions occur per unit of time when volume is kept constant.

Answer: 2. Positive work is done during expansion by the gas against external pressure

Question 117. A gas has:

1. One specific heat only
2. Two specific heats only
3. An infinite number of specific heats
4. No specific heat

Answer: 3. Infinite number of specific heats

Question 118. For a solid with a small expansion coefficient,

1. C_p– C_v= R
2. C_p– C_v= R
3. C_p is slightly greater than C_v
4. C_p is slightly less than C_v

Answer: 3. C_p is slightly greater than C_v

Question 119. When an ideal gas undergoes an adiabatic change causing a temperature change ΔT

1. There is no heat gained or lost by the gas
2. The work done by the gas is equal to the change in internal energy
3. The change in internal energy per mole of the gas is Cv ΔT, where Cvis the molar heat capacity at constant volume.

1. (1), (2), (3) correct
2. (1), (2) correct
3. (1), (3) correct
4. (1) correct

Answer: 3. (1), (3) correct

Question 120. The adiabatic bulk modulus of hydrogen gas (γ = 1.4) at NTP is:

1. 1 × 10⁵ N/m²
2. 1 × 10^-5 N/m²
3. 1.4 N/m²
4. 1.4 × 10⁵ N/m²

Answer: 4. 1.4 × 10⁵ N/m²

Question 121. A given quantity of a gas is at pressure P and absolute temperature T. The isothermal bulk modulus of the gas is:

1. \(\frac{2}{3} P\)
2. P
3. \(\frac{3}{2} P\)
4. 2P

Answer: 2. P

Question 122. A and B are two adiabatic curves for two different gases. Then A and B correspond to:

1. Ar and He respectively
2. He and H₂ respectively
3. O₂ and H₂ respectively
4. H₂ and He respectively

Answer: 2. He and H₂ respectively

Question 123. In a cyclic process shown in the figure an ideal gas is adiabatically taken from B and A., the work done on the gas during the process B → A is 30 J, and when the gas is taken from A → B the heat absorbed by the gas is 20 J. The change in internal energy of the gas in the process A → B is:

1. 20 J
2. – 30 J
3. 50 J
4. – 10 J

Answer: 2. –30 J

Question 124. An ideal gas is allowed to expand freely against a vacuum in a rigid insulated container. The gas undergoes:

1. An increase in its internal energy
2. A decrease in its internal energy
3. Neither an increase nor decrease in temperature or internal energy
4. An increase in temperature

Answer: 1. An increase in its internal energy

Question 125. For free expansion of a gas in an adiabatic container which of the following is true?

1. Q = W = 0 and ΔU = 0
2. Q = 0, W > 0 and ΔU = Q
3. W = 0, Q > 0 and ΔU = Q
4. W = 0, Q < 0 and ΔU = 0

Answer: 1. Q = W = 0 and ΔU = 0

Question 126. In an adiabatic process on a gas with γ = 1.4, the pressure is increased by 0.5%. The volume decreases by about

1. 0.36%
2. 0.5%
3. 0.7&
4. 1%

Answer: 1. 0.36%

Question 127. A fixed mass of an ideal gas undergoes the change represented by XYZX below. Which one of the following sets could describe these changes?

Answer: 4

Question 128. Starting with the same initial conditions, an ideal gas expands from volume V₁ to V₂ in three different ways. The work done by the gas is W₁ if the process is isothermal, W₂ if isobaric and W₃ if adiabatic, then :

1. W₂> W₁> W₃
2. W₂> W₃> W₁
3. W₁> W₂> W₃
4. W₁> W₃> W₂

Answer: 1. W₂> W₁> W₃

Kinetic Theory and Thermodynamics NEET Physics MCQs

Question 129. A gas is expanded from volume V₀ to 2V₀ under three different processes. Process 1 is isobaric, process 2 is isothermal and process 3 is adiabatic. Let ΔU₁, ΔU₂, and ΔU₃ be the change in internal energy of the gas in these three processes. Then:

1. ΔU₁> ΔU₂> ΔU₃
2. ΔU₁< ΔU₂< ΔU₃
3. ΔU₂< ΔU₁< ΔU₃
4. ΔU₂< ΔU₃< ΔU₁

Answer: 1. ΔU₁> ΔU₂> ΔU₃

Question 130. The molar heat capacity for the process shown in fig. is

1. C = C_p
2. C = C_v
3. C > C_v
4. C = 0

Answer: 4. C = 0

Question 131. Find the amount of work done to increase the temperature of one mole of ideal gas by 30ºC. if it is expanding under the condition V ∝ T^2/3 (R = 8.31 J/mol – K):

1. 16.62 J
2. 166.2 J
3. 1662 J
4. 1.662 J

Answer: 2. 166.2 J

Question 132. A gas undergoes a process in which its pressure P and volume V are related as VPⁿ = constant. The bulk modulus of the gas in the process is:

1. no
2. P^1/n
3. P/n
4. Pⁿ

Answer: 3. P/n

Question 133. V = \(k\left(\frac{P}{T}\right)^{0.33}\) where k is constant. It is a,

1. Isothermal process
2. Adiabatic process
3. Isochoric process
4. Isobaric process

Answer: 3. Isochoric process

Question 134. For the adiabatic process of an ideal gas the value of \(\frac{d P}{P}\) is equal to –

1. \(-\gamma \frac{d V}{V}\)
2. \(-\gamma \frac{V}{d V}\)
3. \(\frac{d V}{V}\)
4. \(-\gamma^2 \frac{d V}{V}\)

Answer: 1. \(-\gamma \frac{d V}{V}\)

Question 135. The isobaric modulus of elasticity is –

1. ∞
2. Zero
3. 1
4. \(\frac{C_p}{C_v}\)

Answer: 2. Zero

Question 136. Two samples of a gas A and B initially at the same temperature and pressure, are compressed to half their initial volume, A isothermally and B adiabatically. The final pressure in –

1. A and B will be the same
2. A will be more than in B
3. A will be less than B
4. A will be double that in B

Answer: 3. A will be less than in B

Question 137. The isothermal bulk modulus of elasticity of a gas is 1.5 × 10⁵ N/m². Its adiabatic bulk modulus of elasticity will be if γ = 1.4 –

1. 1.5 × 10⁵ N/m²
2. 3 × 10⁵ N/m²
3. 2.1 × 10⁵ N/m²
4. ∞

Answer: 3. 2.1 × 10⁵ N/m²

Question 138. The pressure and volume of a diatomic gas are P and V respectively. It is compressed suddenly to 1/32 of its initial volume then its final pressure will be –

1. 32 P
2. 128 P
3. P/128
4. P/32

Answer: 2. 128 P

Question 139. The work done by gas in an adiabatic process depends on –

1. Change in temperature
2. Change in volume
3. Change in pressure
4. Change is heat

Answer: 1. Change in temperature

Question 140. The volume of a gas is reduced to 1/4 of its initial volume adiabatically at 27ºC. The final temperature of the gas will be if γ = 1.4 –

1. 300 × (4)0.4 K
2. 100 × (4)0.4 K
3. 27 × (4)0.4 K
4. 300 × (1/4)0.4 K

Answer: 1. 300 × (4)0.4 K

Question 141. 1 m³ of gas is compressed suddenly at atmospheric pressure and temperature 27ºC such that its temperature becomes 627ºC. The final pressure of the gas will be (γ = 1.5)-

1. 27 × 10⁶ N/m²
2. 7.2 × 10⁵ N/m²
3. 2.7 × 10⁵ N/m²
4. 27 × 10⁵ N/m²

Answer: 4. 27 × 105 N/m²

Question 142. If 1 kg air (γ = 1.4) is heated adiabatically from 0ºC to 10ºC then the increase in its internal energy will be (C_v= 0.172 cal/gmºC) –

1. 1720 joule
2. 7224 joule
3. 172 calorie
4. 7224 calorie

Answer: 2. 7224 joule

Question 143. During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The value of γ for the gas is –

1. \(\frac{5}{3}\)
2. \(\frac{7}{5}\)
3. \(\frac{3}{2}\)
4. \(\frac{11}{9}\)

Answer: 3. \(\frac{3}{2}\)

Question 144. 5.6 liter of helium gas at STP is adiabatically compressed to 0.7 liter. Taking the initial temperature to be T₁, the work done in the process is:

1. \(\frac{9}{8} \mathrm{RT}_1\)
2. \(\frac{3}{2} \mathrm{RT}_1\)
3. \(\frac{15}{8} R T_1\)
4. \(\frac{9}{2} R T_1\)

Answer: 1. \(\frac{9}{8} \mathrm{RT}_1\)

Question 145. An ideal gas is expanding such that PT₂ = constant. The coefficient of volume expansion of the gas is

1. \(\frac{1}{\mathrm{~T}}\)
2. \(\frac{2}{\mathrm{~T}}\)
3. \(\frac{3}{\mathrm{~T}}\)
4. \(\frac{4}{\mathrm{~T}}\)

Answer: 3. \(\frac{3}{\mathrm{~T}}\)

Question 146. One mole of an ideal gas at an initial temperature of T K does 6R joules of work adiabatically. If the ratio of specific heats of this gas at constant pressure and constant volume is 5/3, the final temperature of the gas will be :

1. (T + 2.4) K
2. (T – 2.4) K
3. (T + 4) K
4. (T – 4) K

Answer: 4. (T – 4) K

Question 147. 2 moles of He gas γ = 5/3 of 20-litre volume at 27ºC subjected to constant pressure is expanded to double the initial volume. Then, it is adiabatically taken to an initial temperature of 27ºC. What will be the work done in the isobaric process? Also find the final pressure, final volume, and work done in the adiabatic process.

1. 7470 J
2. 7074 J
3. 7070 J
4. 7474 J

Answer: 1. 7470 J

Question 148. A Carnot engine works between 600 K and 300 K. In each cycle of operations, the engine draws 1000 joules of energy from the source at 600 K. The efficiency of the engine is –

1. 20%
2. 50%
3. 70%
4. 90%

Answer: 2. 50%

Question 149. In the above problem, the useful work done by the engine is –

1. 100 joule
2. 500 joule
3. 1000 joule
4. 150 joule

Answer: 2. 500 joule

Question 150. In the above problem, the energy rejected by the sink is –

1. 100 joule
2. 500 joule
3. 1000 joule
4. 300 joule

Answer: 2. 500 joule

Question 151. A Carnot engine works between the ice point and the steam point. Its efficiency will be –

1. 26.81 %
2. 53.36 %
3. 71.23 %
4. 85.42 %

Answer: 1. 26.81 %

Question 152. In the above problem, to increase the efficiency of the engine by 20%, its sink temperature will have to be changed by –

1. Increase by 20 K
2. Decrease by 293 K
3. Increase by 20ºC
4. Decrease by 20ºC

Answer: 4. Decrease by 20ºC

Question 153. In the above problem, to increase the efficiency by 20%, its source temperature will have to be changed by –

1. 402.5 K increase
2. 129.5 K decrease
3. 129.5 ºC increase
4. 129.5 ºC decrease

Answer: 3. 129.5 ºC increase

Question 154. A Cannot engine work between 200ºC and 0ºC. Another Carnot engine works between 0ºC and –200ºC. In both cases, the working substance absorbs 4 kilocalories of heat from the source. The efficiency of the first engine will be –

1. \(\frac{100}{473}\)
2. \(\frac{200}{473}\)
3. \(\frac{200}{273}\)
4. \(\frac{273}{373}\)

Answer: 2. \(\frac{200}{473}\)

Question 155. In the above problem, the efficiency of the second engine will be –

1. \(\frac{100}{273}\)
2. \(\frac{173}{273}\)
3. \(\frac{200}{273}\)
4. \(\frac{273}{373}\)

Answer: 3. \(\frac{200}{273}\)

Question 156. In the above problem, the ratio of efficiencies of two engines will be –

1. 0.18
2. 0.38
3. 0.58
4. 0.78

Answer: 3. 0.58

Question 157. In the above problem, the amount of useful work done by the first engine is –

1. 7.1 × 10³ Joule
2. 3.8 × 10⁴ Joule
3. 5.9 × 10⁵ Joule
4. 9.3 × 10⁶ Joule

Answer: 1. 7.1 × 10³ Joule

Question 158. In the above problem, the output work of the second engine is

1. 2.93 × 10³ calorie
2. 12.3 × 10³ calorie
3. 12.3 × 10³ joule
4. 2.93 × 10³ calorie

Answer: 1. 2.93 × 10³ calorie

NEET Physics Class 11 Chapter 9 MCQs: Kinetic Theory of Gases and Thermodynamics

Question 159. In the above problem, the ratio of outputs of two engines is –

1. 0.577
2. 0.377
3. 0.777
4. 0.177

Answer: 1. 0.577

Question 160. The efficiency of the Carnot engine is 50% and the temperature of the sink is 500 K. If the temperature of the source is kept constant and its efficiency is to be raised to 60%; then the required temperature of the sink will be:

1. 600 K
2. 500 K
3. 400 K
4. 100 K

Answer: 3. 400 K

Question 161. Even the Carnot engine cannot give 100% efficiency because we cannot:

1. Prevent radiation
2. Find ideal sources
3. Reach absolute zero temperature
4. Eliminate friction

Answer: 3. Reach absolute zero temperature

Question 162. “Heat cannot be itself flow from a body at a lower temperature to a body at a higher temperature” is a statement or consequence of :

1. Second law of thermodynamics
2. Conservation of momentum
3. Conservation of mass
4. The first law of thermodynamics

Answer: 1. Second law of thermodynamics

Question 163. A Carnot engine takes 3 × 10⁶ cal of heat from a reservoir at 627ºC and gives it to a sink at 27ºC. The work done by the engine is:

1. 4.2 × 10⁶ J
2. 8.4 × 10⁶ J
3. 16.8 × 10⁶ J
4. Zero

Answer: 2. 8.4 × 106 J

Question 164. In a Carnot engine, the reservoir temperature is 7°C. Its efficiency is 50%. To increase efficiency to 70% by how much temperature of the source is to be raised.

1. 840 K
2. 280 K
3. 560 K
4. 373 K

Answer: 4. 373 K

Question 165. Which statement is incorrect?

1. All reversible cycles have the same efficiency
2. A reversible cycle has more efficiency than an irreversible one
3. Carnot cycle is a reversible one
4. Carnot cycle has the maximum efficiency in all cycles

Answer: 1. All reversible cycles have the same efficiency

Question 166. An ideal gas heat engine operates in cannot cycle between 227ºC and 127ºC. It absorbs 6 × 10⁴ cal of heat at higher temperatures. The amount of heat converted to work is:

1. 2.4 × 10⁴ cal
2. 6 × 10⁴ cal
3. 1.2 × 10⁴ cal
4. 4.8 × 10⁴ cal

Answer: 3. 1.2 × 10⁴ cal

Question 167. A Carnot engine whose sink is at 300 K has an efficiency of 40% By how much should the temperature of the source be increased to increase its efficiency by 50% of the original efficiency:-

1. 275 K
2. 325 K
3. 250 K
4. 380 K

Answer: 3. 250 K

Question 168. An engine has an efficiency of \(\frac{1}{6}\). When the temperature of the sink is reduced by 62ºC, its efficiency is doubled. The temperature of the source is:

1. 124ºC
2. 37ºC
3. 62ºC
4. 99ºC

Answer: 4. 99ºC

Question 169. The temperature-entropy diagram of a reversible engine cycle is given in the figure. Its efficiency is:

1. \(\frac{1}{2}\)
2. \(\frac{1}{4}\)
3. \(\frac{1}{3}\)
4. \(\frac{2}{3}\)

Answer: 3. \(\frac{1}{3}\)

Question 170. A Carnot engine, having an efficiency of η = 1/10 as a heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at a lower temperature is

1. 99 J
2. 90 J
3. 1 J
4. 100 J

Answer: 2. 90 J

Question 171. The work of 146 kJ is performed to compress one-kilo mole of a gas adiabatically and in this process the temperature of the gas increases by 7C. The gas is (R = 8.3 J mol^-1 K^-1)

1. Diatomic
2. Triatomic
3. A mixture of monoatomic and diatomic
4. Monoatomic

Answer: 1. Diatomic

Question 172. A Carnot working between 300K and 600K has a work output of 800 J per cycle. What is the amount of heat energy supplied to the engine from the source per cycle

1. 1800 J/cycle
2. 1000 J/cycle
3. 2000 J/cycle
4. 1600 J/cycle

Answer: 4. 1600 J/cycle

Question 173. The coefficient of performance of a Carnot refrigerator working between 30° C and 0° C is

1. 10
2. 1
3. 9
4. 0

Answer: 3. 9

Question 174. If the door of a refrigerator is kept open then which of the following is true

1. Room is cooled
2. Room is heated
3. The room is either cooled or heated
4. The room is neither cooled nor heated

Answer: 2. Room is heated

NEET Physics MCQs on Thermodynamics and Kinetic Theory for Class 11

Question 175. An Ideal gas heat engine operated in a Carnot’s cycle between 227° C and 127° C. It absorbs 6 × 10⁴ J at high temperatures. The amount of heat converted into work is

1. 4.8 × 10⁴ J
2. 3.5 × 10⁴ J
3. 1.6 × 10⁴ J
4. 1.2 × 10⁴ J

Answer: 4. 1.2 × 10⁴ J

Question 176. An ideal gas heat engine exhausting heat at 77° C does not have a 30% efficiency. It must take the heat at

1. 127° C
2. 227°C
3. 327° C
4. 673°C

Answer: 2. 227°C

Question 177. The efficiency of the Carnot engine is 100% if

1. T₂= 273 K
2. T₂= 0 K
3. T₁= 273 K
4. T₁= 0 K

Answer: 2. T₂= 0 K

Question 178. The efficiency of Carnot’s engine operating between reservoirs, maintained at temperatures 27°C and 123°C, is

1. 50%
2. 24%
3. 0.75%
4. 0.4%

Answer: 1. 50%

Question 179. A Carnot engine operates between 227°C and 27°C. The efficiency of the engine will be

1. \(\frac{1}{3}\)
2. \(\frac{2}{5}\)
3. \(\frac{3}{4}\)
4. \(\frac{3}{5}\)

Answer: 2. \(\frac{2}{5}\)

Question 180. A Carnot engine has the same efficiency between 800 K to 500 K and x K to 600 K. The value of x is

1. 1000 K
2. 960 K
3. 846K
4. 754 K

Answer: 2. 960 K

Question 181. A scientist says that the efficiency of his heat engine which operates at source temperature 127°C and sink temperature 27°C is 26% then

1. It is impossible
2. It is possible but less probable
3. It is quite probable
4. Data are incomplete

Answer: 1. It is impossible

Question 182. A Carnot’s engine is made to work between 200°C and 0°C first and then between 0°C and –200°C. The ratio of efficiencies of the engine in the two cases is

1. 1.73 :1
2. 1:1.73
3. 1:1
4. 1: 2

Answer: 1. 1.73 :1

Question 183. The efficiency of a Carnot engine is 50% when the temperature of the outlet is 500 K. To increase up to 60% keeping the temperature of intake the same what is the temperature of the outlet

1. 200K
2. 400 K
3. 600K
4. 800 K

Answer: 2. 400 K

Question 184. If an ideal flask containing hot coffee is shaken, the temperature of the coffee will:

1. Decrease
2. Increase
3. Remain same
4. Decrease if temperature is below 4ºC and increase if temperature is equal to or more than 4ºC

Answer: 2. Increase

Question 185. An electric fan is switched on in a closed room. The air in the room is

1. Cooled
2. Heated
3. Maintains its temperature
4. Heated or cooled depending on the atmospheric pressure

Answer: 2. Heated

Question 186. A heat engine employing a Carnot cycle with an efficiency of η = 10% is used as a refrigerating machine, the thermal reservoirs being the same. The refrigerating efficiency ∈ is

1. 12
2. 8
3. \(\frac{1}{10}\)
4. 9

Answer: 4. 9

Question 187. An ideal gas is initially at temperature T and volume V. Its volume is increased by ΔV due to an increase in temperature ΔT, with pressure remaining constant. The quantity \(\delta=\frac{\Delta \mathrm{V}}{\mathrm{V} \Delta \mathrm{T}}\) varies with temperature as:

Answer: 3

Question 188. A monoatomic ideal gas, initially at temperature T₁, is enclosed in a cylinder fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature T₂ by releasing the piston suddenly. If L₁ and L₂ are the length of the gas column before and after expansion respectively, Then T₁/T₂ is given by:

1. \(\left(\frac{L_1}{L_2}\right)^{2 / 3}\)
2. \(\frac{\mathrm{L}_1}{\mathrm{~L}_2}\)
3. \(\frac{L_2}{L_1}\)
4. \(\left(\frac{L_2}{L_1}\right)^{2 / 3}\)

Answer: 4. \(\left(\frac{L_2}{L_1}\right)^{2 / 3}\)

Question 189. Which of the following graphs correctly represents the variation of β = –(dV/dP)/V with P for an ideal gas at constant temperature?

Answer: 1

Question 190. An ideal gas undergoes a cyclic process as shown in the given P–T diagram, where the process AC is adiabatic. The process is also represented by :

Answer: 2

Question 191. Statement – 1

The total translational kinetic energy of all the molecules of a given mass of an ideal gas is 1.5 times the product of its pressure and volume. because

Statement – 2

The molecules of a gas collide with each other and the velocities of the molecules change due to the collision.

1. Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1
2. Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1
3. Statement-1 is True, Statement-2 is False
4. Statement-1 is False, and Statement-2 is True.

Answer: 2. Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1

Question 192. One mole of a monatomic ideal gas is taken along two cyclic processes E → F → G → E and E → F → H → E as shown in the PV diagram. The processes involved are purely isochoric, isobaric, isothermal, or adiabatic.

Match the paths in List 1 with the magnitudes of the work done in List 2 and select the correct answer using the codes given below the lists.

Codes:

Answer: 1.

Question 193. Two containers of equal volume contain the same gas at pressure p₁ and p₂ and absolute temperature T₁ and T₂ respectively. On joining the vessels the gas reaches a common pressure p and common temperature T. The ratio p/T is equal to

1. \(\frac{p_1}{T_1}+\frac{p_2}{T_2}\)
2. \(\frac{p_1 T_1+p_2 T_2}{\left(T_1+T_2\right)^2}\)
3. \(\frac{p_1 T_2+p_2 T_1}{\left(T_1+T_2\right)^2}\)
4. \(\frac{\mathrm{p}_1}{2 \mathrm{~T}_1}+\frac{\mathrm{p}_2}{2 \mathrm{~T}_2}\)

Answer: 4. \(\frac{\mathrm{p}_1}{2 \mathrm{~T}_1}+\frac{\mathrm{p}_2}{2 \mathrm{~T}_2}\)

Question 194. If a diatomic gas is supplied heat Q in a process, it performs work \(\frac{Q}{4}\). What is the molar heat capacity of the gas in this process?

1. \(\frac{2}{5} R\)
2. \(\frac{5}{2} R\)
3. \(\frac{10}{3} R\)
4. \(\frac{6}{7} R\)

Answer: 3. \(\frac{10}{3} R\)

Question 195. Two samples of air A and B having the same composition and initially at the same temperature T, pressure P, and volume V are taken. A and B are made to undergo the following process :

Case 1: A and B are compressed from volume V to volume V/2. A is compressed isothermally while B is compressed adiabatically. The final pressures are P_AC and P_BC respectively.

Case: 2 A and B are allowed to undergo expansion from volume V to volume 2V. A undergoes while B undergoes adiabatic expansion. The final pressure of A and B are P_AE and P_BE respectively.

1. P_AC = P_BC and P_AE = P_BE
2. P_AC = P_AE and P_BC = P_BE
3. P_AC > P_BC and P_AE < P_BE
4. P_AC < P_BC and P_AE> P_BE

Answer: 4. P_AC < P_BC and P_AE > P_BE

Question 196. 4 moles of an ideal monoatomic gas occupying volume V is adiabatically expanded from temperature 300 K to a volume of \(2 \sqrt{2} \mathrm{~V}\). Find:

1. Final temperature.
2. Change in internal energy (R = 8.3 J/mol K)

Answer:

1. 150K
2. -7500 J

Question 197. The internal energy change in a system that has absorbed 2 kcal of heat and done 500 J of work is

1. 8900 J
2. 6400 J
3. 5400 J
4. 7900 J

Answer: 4. 7900 J

Question 198. If ΔU and ΔW represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?

1. ΔU = – ΔW, in a adiabatic process
2. ΔU = ΔW, in a isothermal process
3. ΔU = ΔW, in a adiabatic process
4. ΔU = – ΔW, in an isothermal process

Answer: 1. ΔU = – ΔW, in a adiabatic process

Question 199. If Cpand Cvdenote the specific heats (per unit) mass of an ideal gas of molecular weight M, where R is gas constant, then (Mains)]

1. C_p– C_v= R/M²
2. C_p– C_v= R
3. C_p– C_v= R/M
4. C_p– C_v= MR

Answer: 3. C_p– C_v= R/M

Question 200. A monoatomic gas at pressure P₁ and volume V₁ is compressed adiabatically to \(\frac{1}{8} \text { th }\) of its original volume. What is the final pressure of the gas

1. 64P₁
2. P₁
3. 16P₁
4. 32P₁

Answer: 4. 32P₁

Question 201. A mass of diatomic gas (γ = 1.4) at a pressure of 2 atmospheres is compressed adiabatically so that its temperature rises from 27ºC to 927ºC. The pressure of the gas in a final state is:

1. 28 atm
2. 68.7atm
3. 256 atm
4. 8 atm

Answer: 3. 256 atm

NEET Physics Kinetic Theory and Thermodynamics Multiple Choice Questions

Question 202. A thermodynamic system is taken through the cycle ABCD as shown in the figure. Heat rejected by the gas during the cycle is:

1. 2 PV
2. 4 PV
3. 12PV
4. PV

Answer: 1. 2 PV

Question 203. One mole of an ideal gas goes from an initial state A to final state B via two processes: It first undergoes isothermal expansion from volume V to 3V and then its volume is reduced from 3V to V at constant pressure. The correct P-V diagram representing the two processes is:

Answer: 4

Question 204. An ideal gas goes from state A to state B via three different processes as indicated in the P-V diagram:

If Q₁, Q₂, Q₃ indicate the heat absorbed by the gas along the three processes and ΔU₁, ΔU₂, and ΔU₃ indicate the change in internal energy along the three processes respectively, then

1. Q₁> Q₂> Q₃ and ΔU₁= ΔU₂= ΔU₃
2. Q₃> Q₂> Q1and ΔU₁= ΔU₂= ΔU₃
3. Q₁= Q₂= Q₃ and ΔU₁> ΔU₂> ΔU₃
4. Q₃> Q₂> Q₁ and ΔU₁> ΔU₂> ΔU₃

Answer: 1. Q₁> Q₂> Q₃ and ΔU₁= ΔU₂= ΔU₃

Question 205. A gas is taken through the cycle A → B → C → A, as shown. What is the net work done by the gas?

1. 1000 J
2. Zero
3. –2000 J
4. 2000 J

Answer: 1. 1000 J

Question 206. In the given (V–T) diagram, what is the relation between pressure P₁ and P₂?

1. P₂> P₁
2. P₂< P₁
3. Cannot be predicted
4. P₂= P₁

Answer: 2. P₂< P₁

Question 207. The molar-specific heats of an ideal gas at constant pressure and volume are denoted by C_p and C_v, respectively. If γ = \(\frac{C_p}{C_v}\) and R is the universal gas constant, then C_v is equal to:

1. \(\frac{R}{(\gamma-1)}\)
2. \(\frac{(\gamma-1)}{R}\)
3. \(\gamma R\)
4. \(\frac{1+\gamma}{1-\gamma}\)

Answer: 1. \(\frac{R}{(\gamma-1)}\)

Question 208. The amount of heat energy required to raise the temperature of 1g of Helium at NTP, from T₁K to T₂K is:

1. \(\frac{3}{2} \mathrm{~N}_{\mathrm{a}} \mathrm{k}_{\mathrm{B}}\left(\mathrm{T}_2-\mathrm{T}_1\right)\)
2. \(\frac{3}{4} \mathrm{~N}_{\mathrm{a}} \mathrm{k}_{\mathrm{B}}\left(\mathrm{T}_2-\mathrm{T}_1\right)\)
3. \(\frac{3}{4} N_a k_B \frac{T_2}{T_1}\)
4. \(\frac{3}{8} N_a k_B\left(T_2-T_1\right)\)

Answer: 4. \(\frac{3}{8} N_a k_B\left(T_2-T_1\right)\)

Question 209. During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its temperature. The ratio of \(\frac{C_p}{C_v}\) for the gas is:

1. 2
2. \(\frac{5}{3}\)
3. \(\frac{3}{2}\)
4. \(\frac{4}{3}\)

Answer: 3. \(\frac{3}{2}\)

Question 210. The mean free path of molecules of a gas (radius ‘r’) is inversely proportional to:

1. r³
2. r²
3. r
4. \(\sqrt{r}\)

Answer: 2. r2

Question 211. One mole of an ideal diatomic gas undergoes a transition from A to B along a path AB as shown in the figure,

The change in internal energy of the gas during the transition is:

1. –20 kJ
2. 20 J
3. – 12 kJ
4. 20 kJ

Answer: 1. –20 kJ

Question 212. A Carnot engine, having an efficiency of η=\(\frac{1}{10}\) as a heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at a lower temperature is:

1. 99 J
2. 90 J
3. 1 J
4. 100 J

Answer: 2. 90 J

Question 213. The ratio of the specific heats \(\frac{C_P}{C_v}\)= γin terms of degrees of freedom (n) is given by:

1. \(\left(1+\frac{n}{3}\right)\)
2. \(\left(1+\frac{2}{n}\right)\)
3. \(\left(1+\frac{n}{2}\right)\)
4. \(\left(1+\frac{1}{n}\right)\)

Answer: 2. \(\left(1+\frac{2}{n}\right)\)

Question 214. The figure below shows two paths that may be taken by a gas to go from a state A to a state C.

In process AB, 400J of heat is added to the system, and in process BC, 100 J of heat is added to the system. The heat absorbed by the system in the process of AC will be:

1. 500 J
2. 460 J
3. 300 J
4. 380 J

Answer: 2. 460 J

Question 215. An ideal gas is compressed to half its initial volume using several processes. Which of the processes results in the maximum work done on the gas?

1. Isobaric
2. Isochoric
3. Isothermal
4. Adiabatic

Answer: 4. Adiabatic

Question 216. The coefficient of performance of a refrigerator is 5 if the temperature inside the freezer is –20°C, and the temperature of the surroundings to which it rejects heat is

1. 41°C
2. 11°C
3. 21°C
4. 31°C

Answer: 4. 31°C

Question 217. Two vessels separately contain two ideal gases A and B at the same temperature the pressure of A being twice that of B. Under such conditions, the density of A is found to be 1.5 times the density of B. The ratio of molecular weight of A and B is:

1. \(\frac{3}{4}\)
2. 2
3. \(\frac{1}{2}\)
4. \(\frac{2}{3}\)

Answer: 1. \(\frac{3}{4}\)

Question 218. A gas is compressed isothermally to half its initial volume. The same gas is compressed separately through an adiabatic process until its volume is again reduced to half. Then:

1. Which of the cases (whether compression through isothermal or through an adiabatic process) requires more work will depend upon the atomicity of the gas
2. Compressing the gas isothermally will require more work to be done
3. Compressing the gas through an adiabatic process will require more work to be done
4. Compressing the gas isothermally or adiabatically will require the same amount of work

Answer: 3. Compressing the gas through adiabatic process will require more work to be done

Question 219. The molecules of a given mass of a gas have r.m.s. velocity of 200 ms^-1 at 27ºC and 1.0×10⁵ Nm^-2 pressure. When the temperature and pressure of the gas are respectively, 127ºC and 0.05×10⁵ Nm², the r.m.s. velocity of velocity of its molecules in ms^-1 is;

1. \(\frac{100}{3}\)
2. \(100 \sqrt{2}\)
3. \(\frac{400}{\sqrt{3}}\)
4. \(\frac{100 \sqrt{2}}{3}\)

Answer: 3. \(\frac{400}{\sqrt{3}}\)

Question 220. One mole of an ideal monatomic gas undergoes a process described by the equation PV³ = constant. The heat capacity of the gas during this process is :

1. R
2. \(\frac{3}{2} R\)
3. \(\frac{5}{2} R\)
4. 2R

Answer: 1. R

Question 221. The temperature inside a refrigerator is t₂ ºC and the room temperature is t₁ ºC. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be

1. \(\frac{t_1+t_2}{t_1+273}\)
2. \(\frac{t_1}{t_1-t_2}\)
3. \(\frac{t_1+273}{t_1-t_2}\)
4. \(\frac{t_2+273}{t_1-t_2}\)

Answer: 3. \(\frac{t_1+273}{t_1-t_2}\)

Question 222. A given sample of an ideal gas occupies a volume V at a pressure P and absolute temperature T. The mass of each molecule of the gas is m. Which of the following gives the density of the gas?

1. mkT
2. P / (kT)
3. Pm / (kT)
4. P / (kTV)

Answer: 3. Pm / (kT)

Question 223. Thermodynamic processes are indicated in the following diagram:

Match the following :

1. 1 → A 2 → C, 3 → D, 4 → B
2. 1 → C, 2 → A, 3 → D, 4 → B
3. 1 → C, 2 → D, 3 → B, 4 → A
4. 1 → D, 2 → B, 3 → A, 4 → C

Answer: 2. 1 → C, 2 → A, 3 → D, 4 → B

Question 224. A gas mixture consists of 2 moles of O₂ and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is:

1. 4 RT
2. 15 RT
3. 9 RT
4. 11 RT

Answer: 4. 11 RT

Question 225. A Carnot engine having an efficiency of \(\frac{1}{10}\) as a heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at a lower temperature is:

1. 1 J
2. 90 J
3. 99 J
4. 100 J

Answer: 2. 90 J

Question 226. The volume (V) of a monatomic gas varies with its temperature (T), as shown in the graph. The ratio of work done by the gas, to the heat absorbed by it, when it undergoes a change from state A to state B, is

1. \(\frac{2}{5}\)
2. \(\frac{2}{7}\)
3. \(\frac{1}{3}\)
4. \(\frac{2}{3}\)

Answer: 1. \(\frac{2}{5}\)

Question 227. The efficiency of an ideal heat engine working between the freezing point and boiling point of water is

1. 26.8 %
2. 12.5 %
3. 6.25 %
4. 20 %

Answer: 1. 26.8 %

Question 228. At what temperature will the rms speed of oxygen molecules become just sufficient for escaping from the Earth’s atmosphere? (Given mass of oxygen molecule (m) = 2.76 × 10^-26 kg Boltzmann’s constant kB =1.38×10^-23 JK^-1

1. 2.508×10⁴ K
2. 1.254×10⁴ K
3. 5.016×10⁴ K
4. 8.360×10⁴ K

Answer: 4. 8.360×10⁴ K

Question 229. In which of the following processes, heat is neither absorbed nor released by a system?

1. Isochoric
2. Isothermal
3. Adiabatic
4. Isobaric

Answer: 3. Adiabatic

Question 230. An increase in the temperature of a gas-filled container would lead to the:

1. Decrease in intermolecular distance
2. Increase in its mass
3. Increase in its kinetic energy
4. Decrease in its pressure

Answer: 3. Increase in its kinetic energy

Question 231. The value of \(\gamma\left(=\frac{C_p}{C_v}\right)\), for hydrogen helium and another ideal diatomic gas X (whose molecules are not rigid but have an additional vibrational mode), are respectively equal to,

1. \(\frac{7}{5}, \frac{5}{3}, \frac{9}{7}\)
2. \(\frac{5}{3}, \frac{7}{5}, \frac{9}{7}\)
3. \(\frac{5}{3}, \frac{7}{5}, \frac{7}{5}\)
4. \(\frac{7}{5}, \frac{5}{3}, \frac{7}{5}\)

Answer: 1. \(\frac{7}{5}, \frac{5}{3}, \frac{9}{7}\)

Question 232. 1 g of water, of volume 1 cm³ at 100ºC, is converted into steam at the same temperature under normal atmospheric pressure ≈1 ×10⁵ Pa. The volume of steam formed equals 1671 cm³. If the specific latent heat of vaporization of water is 2256 J/g, the change in internal energy is:

1. 2423 J
2. 2089 J
3. 167 J
4. 2256 J

Answer: 2. 2089 J

Question 233. The efficiency of a Carnot engine depends upon

1. The temperature of the sink only
2. The temperatures of the source and sink
3. The volume of the cylinder of the engine
4. The temperature of the source only

Answer: 4. The temperature of the source only

Question 234. The P-V diagram for an ideal gas in a piston-cylinder assembly undergoing a thermodynamic process is shown in the figure. The process is

1. Adiabatic
2. Isochoric
3. Isobaric
4. Isothermal

Answer: 4. Isothermal

Question 235. The quantities of heat required to raise the temperature of two solid copper spheres of radii r₁ and r₂ (r₁ = 1.5 r₂) through 1K are in the ratio

1. \(\frac{5}{3}\)
2. \(\frac{27}{8}\)
3. \(\frac{9}{4}\)
4. \(\frac{3}{2}\)

Answer: 3. \(\frac{9}{4}\)

Question 236. Two cylinders A and B of equal capacity are connected via a stop cock. A contains an ideal gas at standard temperature and pressure. B is completely evacuated. The entire system is thermally insulated. The stop cock is suddenly opened. The process is

1. Isobaric
2. Isothermal
3. Adiabatic
4. Isochoric

Answer: 4. Isochoric

Question 237. The mean free path for a gas molecule depends upon the diameter, d of the molecule as

1. \(\ell \propto \frac{1}{\mathrm{~d}^2}\)
2. \(\ell \propto d\)
3. \(\ell \propto \mathrm{d}^2\)
4. \(\ell \propto \frac{1}{d}\)

Answer: 1. \(\ell \propto \frac{1}{\mathrm{~d}^2}\)

Question 238. The average thermal energy for a mono-atomic gas is : (kB is Boltzmann constant and T, absolute temperature)

1. \(\frac{7}{2} k_B T\)
2. \(\frac{1}{2} k_B T\)
3. \(\frac{3}{2} k_B T\)
4. \(\frac{5}{2} k_B T\)

Answer: 3. \(\frac{3}{2} k_B T\)

Question 239. The mean free path for a gas, with molecular diameter d and number density n, can be expressed as

1. \(\frac{1}{\sqrt{2} n^2 \pi^2 d^2}\)
2. \(\frac{1}{\sqrt{2} n \pi d}\)
3. \(\frac{1}{\sqrt{2} n \pi d^2}\)
4. \(\frac{1}{\sqrt{2} n^2 \pi d^2}\)

Answer: 3. \(\frac{1}{\sqrt{2} n \pi d^2}\)

Question 240. Match Column-1 and Column-2 and choose the correct match from the given choices.

1. 1–Q, 2–R, 3–S, 4–P
2. 1–Q, 2–P, 3–S, 4–R
3. 1–R, 2–Q, 3–P, 4–S
4. 1–R, 2–P, 3–S, 4–Q

Answer: 2. 1–Q, 2–P, 3–S, 4–R

Class 11 NEET Physics Kinetic Theory of Gases and Thermodynamics Practice MCQs

Question 241. n moles of a monoatomic gas is carried around the reversible rectangular cycle ABCDA as shown in the diagram. The temperature at A is T₀. The thermodynamic efficiency of the cycle is

1. 15%
2. 50%
3. 20%
4. 25%

Answer: 2. 50%

Question 242. An engine has an efficiency of 1/6. When the temperature of the sink is reduced by 62ºC, its efficiency is doubled. The temperature of the source will be

1. 37ºC
2. 62ºC
3. 99ºC
4. 124ºC

Answer: 3. 99ºC

Question 243. Assertion: The melting point of ice decreases with the increase of pressure. Reason: Ice contracts on melting.

1. If both assertion and reason are true and reason is the correct explanation of assertion.
2. If both assertion and reason are true but reason is not the correct explanation of assertion.
3. If Assertion is true but the reason is false.
4. If both assertion and reason are false.

Answer: 1. If both assertion and reason are true and reason is the correct explanation of assertion.

Question 244. 1 mole of H₂ gas is contained in a box of volume V = 1.00 m³ at T = 300 K. The gas is heated to a temperature of T = 3000 K and the gas gets converted to a gas of hydrogen atoms. The final pressure would be (considering all gases to be ideal)

1. Same as the pressure initially
2. 2 times the pressure initially
3. 10 times the pressure initially
4. 20 times the pressure initially

Answer: 4. 20 times the pressure initially

Question 245. Assume the gas to be ideal the work done on the gas in taking it from A to B is :

1. 200 R
2. 300 R
3. 400 R
4. 500 R

Answer: 3. 400 R

Question 246. The work done on the gas in taking it from D to A is

1. –414 R
2. + 414 R
3. – 690 R
4. + 690 R

Answer: 2. + 414 R

Question 247. The net work done on the gas in the cycle ABCDA is:

1. Zero
2. 276 R
3. 1076 R
4. 1904 R

Answer: 2. 276 R

Question 248. One kg of a diatomic gas is at a pressure of 8 × 104 N/m². The density of the gas is 4 kg/m³. What is the energy of the gas due to its thermal motion?

1. 5 × 10⁴J
2. 6 × 10⁴J
3. 7 × 10⁴J
4. 3 × 10⁴J

Answer: 1. 5 × 10⁴J

Question 249. A diatomic ideal gas is used in a Carnot engine as the working substance. If during the adiabatic expansion part of the cycle, the volume of the gas increases from V to 32 V, the efficiency of the engine is:

1. 0.5
2. 0.75
3. 0.99
4. 0.25

Answer: 2. 0.75

Question 250. A Carnot engine operating between temperatures T₁ and T₂ has effeiciency \(\frac{1}{6}\). When T₂ is lowered by 62 K, its efficiency increases to \(\frac{1}{3}\). Then T₁ and T₂ are, respectively:

1. 372 K and 310 K
2. 372 K and 330 K
3. 330 K and 268 K
4. 310 K and 248 K

Answer: 1. 372 K and 310 K

Question 251. Three perfect gases at absolute temperatures T₁, T_2, and T₃ are mixed. The masses of molecules are m₁, m_2, and m₃ and the number of molecules is n₁,n_2, and n₃ respectively. Assuming no loss of energy, the final temperature of the mixture is:

1. \(\frac{\left(\mathrm{T}_1+\mathrm{T}_2+\mathrm{T}_3\right)}{3}\)
2. \(\frac{\mathrm{n}_1 \mathrm{~T}_1+\mathrm{n}_2 \mathrm{~T}_2+\mathrm{n}_3 \mathrm{~T}_3}{\mathrm{n}_1+\mathrm{n}_2+\mathrm{n}_3}\)
3. \(\frac{n_1 T_1^2+n_2 T_2^2+n_3 T_3^2}{n_1 T_1+n_2 T_2+n_3 T_3}\)
4. \(\frac{n_1^2 T_1^2+n_2^2 T_2^2+n_3^2 T_3^2}{n_1 T_1+n_2 T_2+n_3 T_3}\)

Answer: 2. \(\frac{\mathrm{n}_1 \mathrm{~T}_1+\mathrm{n}_2 \mathrm{~T}_2+\mathrm{n}_3 \mathrm{~T}_3}{\mathrm{n}_1+\mathrm{n}_2+\mathrm{n}_3}\)

Question 252. A thermally insulated vessel contains an ideal gas of molecular mass M and a ratio of specific heat γ. It is moving with speed v and is suddenly brought to rest. Assuming no heat is lost to the surroundings, its temperature increases by :

1. \(\frac{(\gamma-1)}{2(\gamma+1) R} M v^2 K\)
2. \(\frac{(\gamma-1)}{2 \gamma R} M^2 K\)
3. \(\frac{\gamma M v^2}{2 R} K\)
4. \(\frac{(\gamma-1)}{2 R} M^2 K\)

Answer: 4. \(\frac{(\gamma-1)}{2 R} M^2 K\)

Question 253. A container with insulating walls is divided into equal parts by a partition fitted with a valve. One part is filled with an ideal gas at a pressure P and temperature T, whereas the other part is completely evacuated. If the valve is suddenly opened, the pressure and temperature of the gas will be:

1. \(\frac{P}{2}, \frac{T}{2}\)
2. P, T
3. \(P, \frac{T}{2}\)
4. \(\frac{P}{2}, T\)

Answer: 4. \(\frac{P}{2}, T\)

Question 254. Helium gas goes through a cycle ABCDA (consisting of two isochoric and isobaric lines) as shown in the figure. The efficiency of this cycle is nearly : (Assume the gas to be close to ideal gas)

1. 15.4%
2. 9.1%
3. 10.5%
4. 12.5%

Answer: 1. 15.4%

Question 255. A Carnot engine, whose efficiency is 40%, takes in heat from a source maintained at a temperature of 500K. It is desired to have an engine of efficiency of 60%. Then, the intake temperature for the same exhaust (sink) temperature must be:

1. The efficiency of the Carnot engine cannot be made larger than 50%
2. 1200 K
3. 750 K
4. 600 K

Answer: 3. 750 K

Question 256. The above p-v diagram represents the thermodynamic cycle of an engine, operating with an ideal monoatomic gas. The amount of heat, extracted from the source in a single cycle is:

1. \(\mathrm{P}_0 \mathrm{v}_0\)
2. \(\left(\frac{13}{2}\right) p_0 \mathrm{v}_0\)
3. \(\left(\frac{11}{2}\right) \mathrm{P}_0 \mathrm{v}_0\)
4. \(4 p_0 v_0\)

Answer: 2. \(\left(\frac{13}{2}\right) p_0 \mathrm{v}_0\)

Question 257. One mole of diatomic ideal gas undergoes a cyclic process ABC as shown in the figure. The process BC is adiabatic. The temperatures at A, B, and C are 400K, 800K, and 600 K respectively. Choose the correct statement:

1. The change in internal energy in the whole cyclic process is 250 R.
2. The change in internal energy in the process CA is 700 R
3. The change in internal energy in the process AB is – 350 R
4. The change in internal energy in the process BC is – 500 R

Answer: 4. The change in internal energy in the process BC is – 500 R

Question 258. An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level. The open end of the tube is then closed and sealed and the tube is raised vertically up by an additional 46 cm. What will be the length of the air column above the mercury in the tube now? (Atmospheric pressure = 76 cm of Hg)

1. 16 cm
2. 22 cm
3. 38 cm
4. 6 cm

Answer: 1. 16 cm

Question 259. Consider a spherical shell of radius R at temperature T. The black body radiation inside it can be considered as an ideal gas of photons with internal energy per unit volume u = \(\frac{U}{V} \propto T^4\) and pressure P = \(\frac{1}{3}\left(\frac{U}{V}\right)\). If the shell now undergoes an adiabatic expansion the relation between T and R is

1. \(\mathrm{T} \propto \mathrm{e}^{-\mathrm{R}}\)
2. \(T \propto e^{-3 R}\)
3. \(T \propto \frac{1}{R}\)
4. \(\mathrm{T} \propto \frac{1}{\mathrm{R}^3}\)

Answer: 3. \(T \propto \frac{1}{R}\)

Question 260. A solid body of constant heat capacity 1 J/°C is being heated by keeping it in contact with reservoirs in two ways:

1. Sequentially keeping in contact with 2 reservoirs so that each reservoir supplies the same amount of heat.
2. Sequentially keeping in contact with 8 reservoirs, each reservoir supplies the same amount of heat.
3. In both cases, the body is brought from the initial temperature of 100°C to the final temperature of 200°C. Entropy changes of the body in the two cases respectively is

1. ln 2, 4ln2
2. ln 2, ln 2
3. ln 2, 2 ln 2
4. 2 ln 2, 8 ln 2

Answer: 2. ln 2, ln 2

Question 261. Consider an ideal gas confined in an isolated closed chamber. As the gas undergoes an adiabatic expansion, the average time of collision between molecules increases as Vq, where V is the volume of the gas. The value of q is \(\left(\gamma=\frac{C_P}{C_V}\right)\)

1. \(\frac{3 \gamma+5}{6}\)
2. \(\frac{3 \gamma-5}{6}\)
3. \(\frac{\gamma+1}{2}\)
4. \(\frac{\gamma-1}{2}\)

Answer: 3. \(\frac{\gamma+1}{2}\)

Question 262. ‘n’ moles of an ideal gas undergoes a process A▢B as shown in the figure. The maximum temperature of the gas during the process will be:

1. \(\frac{3 P_0 V_0}{2 n R}\)
2. \(\frac{9 P_0 V_0}{2 n R}\)
3. \(\frac{9 P_0 V_0}{n R}\)
4. \(\frac{9 P_0 V_0}{4 n R}\)

Answer: 4. \(\frac{9 P_0 V_0}{4 n R}\)

Question 263. Cp and Cv are specific heats at constant pressure and constant volume respectively. It is observed that

Cp – Cv = a for hydrogen gas

Cp – Cv = b for nitrogen gas

The correct relation between a and b is:

1. a = 28 b
2. \(a=\frac{1}{14} b\)
3. a = b
4. a = 14 b

Answer: 4. a = 14 b

Question 264. The temperature of an open room of volume 30 m³ increased from 17ºC to 27ºC due to the sunshine. The atmospheric pressure in the room remains 1 × 10⁵ Pa. If ni and nf are the number of molecules in the room before and after heating, then nf – ni will be:

1. – 2.5 × 10²⁵
2. – 1.61 × 10²³
3. 1.38 × 10²³
4. 2.5 × 10²⁵

Answer: 1. – 2.5 × 10²⁵

Question 265. Two moles of an ideal monoatomic gas occupy a volume V at 27°C. The gas expands adiabatically to a volume of 2V. Calculate

1. The final temperature of the gas and
2. Change in its internal energy.

1. (1) 189 K (2) –2.7 kJ
2. (1) 195 K (2) 2.7 kJ
3. (1) 189 K (2) 2.7 kJ
4. (1) 195 K (2) –2.7 kj

Answer: 1. (1) 189 K (2) –2.7 kJ

Question 266. A mixture of 2 moles of helium gas (atomic mass = 4u) and 1 mole of argon gas (atomic mass = 40u) is kept at 300 K in a container, the ratio of their rms speeds \(\left[\frac{\mathrm{v}_{\mathrm{rms}}(\text { helium })}{\mathrm{V}_{\mathrm{rms}}(\text { argon })}\right]\), is close to:

1. 0.32
2. 3.16
3. 2.24
4. 0.45

Answer: 2. 3.16

Question 267. A gas can be taken from A to B via two different processes ACB and ADB. When path ACB is used 60J of heat flows into the system and 30J of work is done by the system. If path ADB is used work done by the system is 10J. The heat flow into the system in path ADB is:

1. 80J
2. 100J
3. 20J
4. 40J

Answer: 4. 40J

NEET Physics Class 11 Chapter 9 Kinetic Theory of Gases and Thermodynamics MCQs

Question 268. A 15 g mass of nitrogen gas is enclosed in a vessel at a temperature of 27º C. Amount of heat transferred to the gas so that the rms velocity of molecules is doubled, is about: [Take R = 8.3 J/K mole]

1. 0.9 kJ
2. 6 kJ
3. 14 kJ
4. 10 kJ

Answer: 4. 10 kJ

Question 269. Three Carnot engines operate in series between a heat source at temperature T₁ and a heat sink at temperature T₄ (see figure). There are two other reservoirs at temperatures T₂ and T₃ as shown, with T₁ > T₂ > T₃ > T₄. The three engines are equally efficient if:

1. \(\mathrm{T}_2=\left(\mathrm{T}_1 \mathrm{~T}_4^2\right)^{1 / 3} ; \mathrm{T}_3=\left(\mathrm{T}_1^2 \mathrm{~T}_4\right)^{1 / 3}\)
2. \(T_2=\left(T_1 T_4\right)^{1 / 2} ; T_3=\left(\mathrm{T}_1^2 \mathrm{~T}_4\right)^{1 / 3}\)
3. \(T_2=\left(\mathrm{T}_1^3 \mathrm{~T}_4\right)^{1 / 4} ; \mathrm{T}_3=\left(\mathrm{T}_1 \mathrm{~T}_4^3\right)^{1 / 4}\)
4. \(T_2=\left(T_1^2 T_4\right)^{1 / 3} ; T_3=\left(T_1 T_4^2\right)^{1 / 3}\)

Answer: 4. \(T_2=\left(T_1^2 T_4\right)^{1 / 3} ; T_3=\left(T_1 T_4^2\right)^{1 / 3}\)

Question 230. Two kg of a monoatomic gas is at a pressure of 4 × 10⁴ N/m². The density of the gas is 8 kg/m³. What is the order of energy of the gas due to its thermal motion?

1. 105 J
2. 104 J
3. 106 J
4. 103 J

Answer: 4. 103 J

Question 231. Half a mole of an ideal monoatomic gas is heated at a constant pressure of 1 atom from 20°C to 90°C. Work done by the gas is close to: (Gas constant R = 831 J/mol.K)

1. 581 J
2. 146 J
3. 291 J
4. 73 J

Answer: 3. 291 J

Question 232. When 100g of liquid A at 100°C is added to 50 g of liquid B at a temperature of 75°C, the temperature of the mixture becomes 90°C. The temperature of the mixture, if 100g of liquid A at 100°C is added to 50 g of liquid B at 50°C, will be:

1. 80°C
2. 60°C
3. 70°C
4. 85°C

Answer: 1. 80°C

Question 233. A rigid diatomic ideal gas undergoes an adiabatic process at room temperature. The relation between temperature and volume for this process is TVx = constant, then x is:

1. \(\frac{2}{5}\)
2. \(\frac{5}{3}\)
3. \(\frac{3}{5}\)
4. \(\frac{2}{3}\)

Answer: 1. \(\frac{2}{5}\)

NEET Physics Class 11 Chapter 9 Kinetic Theory of Gases and Thermodynamics MCQs

Question 234. An ideal gas enclosed in a cylinder at a pressure of 2 atm and temperature, of 300 K. The mean time between two successive collisions is 6 × 10–8 s. If the pressure is doubled and temperature is increased to 500 K, the mean time between two successive collisions will be close to:

1. 3 × 10^-6 s
2. 4 × 10^-8 s
3. 2 × 10^-7 s
4. 05 × 10^-8 s

Answer: 2. 4 × 10^-8 s

Question 235. A vertical closed cylinder is separated into two parts by a frictionless piston of mass m and negligible thickness. The piston is free to move along the length of the cylinder. The length of the cylinder above the piston is l₁, and that below the piston is l₂, such that l₁ > l₂. Each part of the cylinder contains n moles of an ideal gas at equal temperature T. If the piston is stationary, its mass, m, will be given by:

(R is the universal gas constant g is the acceleration due to gravity.)

1. \(\frac{\mathrm{RT}}{\mathrm{g}}\left[\frac{2 \ell_1+\ell_2}{\ell_1 \ell_2}\right]\)
2. \(\frac{\mathrm{RT}}{\mathrm{ng}}\left[\frac{\ell_1-3 \ell_2}{\ell_1 \ell_2}\right]\)
3. \(\frac{\mathrm{nRT}}{\mathrm{g}}\left[\frac{1}{\ell_2}+\frac{1}{\ell_1}\right]\)
4. \(\frac{\mathrm{nRT}}{\mathrm{g}}\left[\frac{\ell_1-\ell_2}{\ell_1 \ell_2}\right]\)

Answer: 4. \(\frac{\mathrm{nRT}}{\mathrm{g}}\left[\frac{\ell_1-\ell_2}{\ell_1 \ell_2}\right]\)

NEET Physics Class 11 Chapter 7 Gravitation Multiple Choice Question Ans Answers

Question 1. Weight of an object is :

1. Normal reaction between ground and the object
2. Gravitational force exerted by earth on the object.
3. Dependent on frame of reference.
4. Net force on the object

Answer: 2. Gravitational force exerted by earth on the object

Question 2. The weight of a body at the centre of the earth is –

1. Zero
2. Infinite
3. Same as on the surface of earth
4. None of the above

Answer: 1. Zero

Question 3. If the distance between two masses is doubled, the gravitational attraction between them.

1. Is doubled
2. Becomes four times
3. Is reduced to half
4. Is reduced to a quarter

Answer: 4. Is reduced to a quarter

Question 4. The gravitational force between two stones of mass 1 kg each separated by a distance of 1 metre in vacuum is –

1. Zero
2. 6.675 × 10^-5 Newton
3. 6.675 × 10^-11 Newton
4. 6.675 × 10^-8 Newton

Answer: 3. 6.675 × 10^-11 newton

Gravitation MCQs for NEET Physics Class 11 with Answers

Question 5. Two particles of equal mass go round a circle of radius R under the action of their mutual gravitational attraction. The speed of each particle is –

1. \(\mathrm{v}=\frac{1}{2 R} \sqrt{\frac{1}{G m}}\)
2. \(\mathrm{v}=\sqrt{\frac{G m}{2 R}}\)
3. \(\mathrm{v}=\frac{1}{2} \sqrt{\frac{G m}{R}}\)
4. \(\mathrm{v}=\sqrt{\frac{4 G m}{R}}\)

Answer: 3. \(\mathrm{v}=\frac{1}{2} \sqrt{\frac{G m}{R}}\)

Question 6. Reason of weightlessness in a satellite is –

1. Zero gravity
2. Centre of mass
3. Zero reaction force by satellite surface
4. None

Answer: 3. Zero reaction force by satellite surface

Question 7. The gravitational force Fgbetween two objects does not depend on –

1. Sum of the masses
2. Product of the masses
3. Gravitational constant
4. Distance between the masses

Answer: 1. Sum of the masses

Question 8. A mass M splits into two parts m and (M – m), which are then separated by a certain distance. What ratio (m/M) maximies the gravitational force between the parts?

1. \(\frac{2}{3}\)
2. \(\frac{3}{4}\)
3. \(\frac{1}{2}\)
4. \(\frac{1}{3}\)

Answer: 3. \(\frac{1}{2}\)

Question 9. On a planet (whose size is the same as that of Earth and mass 4 times of the Earth) the energy needed to lift a 2kg mass vertically upwards through a 2m distance on the planet is (g = 10m/sec² on surface of earth)

1. 16 J
2. 32 J
3. 160 J
4. 320 J

Answer: 3. 160 J

Question 10. The dimensions of universal gravitational constant are :

1. [M^-1L³T^-2]
2. [ML²T^-1]
3. [M^-2L³T^-2]
4. [M^-2L²T^-1]

Answer: 1. [M^-1L³T^-2]

Question 11. If the change in the value of ‘g’ at a height h above the surface of the earth is the same as at a depth x below it, then (both x and h being much smaller than the radius of the earth) –

1. x = h
2. x = 2h
3. x = \(\frac{h}{2}\)
4. x = h²

Answer: 2. x = 2h

Question 12. The moon’s radius is 1/4 that of the Earth and its mass is 1/80 time that of the earth. If g represents the acceleration due to gravity on the surface of the earth, that on the surface of the moon is

1. g/4
2. g/5
3. g/6
4. g/8

Answer: 2. g/5

Question 13. Assuming the earth to be a homogeneous sphere of radius R, its density in terms of G (constant of gravitation) and g (acceleration due to gravity on the surface of the earth) is

1. 3g/(4πRG)
2. 4πg/(3RG)
3. 4πRg/(3G)
4. 4πRG/(3g)

Answer: 1. 3g/(4πRG)

Question 14. An object is placed at a distance of R/2 from the centre of earth. Knowing mass is distributed uniformly, acceleration of that object due to gravity at that point is: (g = acceleration due to gravity on the surface of earth and R is the radius of earth)

1. g
2. 2 g
3. g/2
4. None of these

Answer: 3. g/2

Question 15. Altitude at which acceleration due to gravity decreases by 0.1% approximately : (Radius of earth = 6400 km)

1. 3.2 km
2. 6.4 km
3. 2.4 km
4. 1.6 km

Answer: 1. 3.2 km

Question 16. An iron ball and a wooden ball of the same radius are released from a height ‘h’ in vacuum. The time taken by both of them to reach the ground is –

1. Unequal
2. Exactly equal
3. Roughly equal
4. Zero

Answer: 2. Exactly equal

Question 17. The correct answer to above question is based on –

1. Acceleration due to gravity in vacuum is same irrespective of size and mass of the body
2. Acceleration due to gravity in v
3. acuum depends on the mass of the body
4. There is no acceleration due to gravity in vacuum
5. In vacuum there is resistance offered to the motion of the body and this resistance depends on the mass of the body

Answer: 1. Acceleration due to gravity in vacuum is same irrespective of size and mass of the body

Question 18. When a body is taken from the equator to the poles, its appearent weight –

1. Remains constant
2. Increases
3. Decreases
4. Increases at N-pole and decreases at S-pole

Answer: 2. Increases

Question 19. A body of mass m is taken to the bottom of a deep mine. Then –

1. Its mass increases
2. Its mass decreases
3. Its weight increases
4. Its weight decreases

Answer: 4. Its weight decreases

Question 20. As we go from the equator to the poles, the value of g

1. Remains the same
2. Decreases
3. Increases
4. Decreases upto a latitude of 45º

Answer: 3. Increases

Question 21. Force of gravity is least at

1. The equator
2. The poles
3. A point in between equator and any pole
4. None of these

Answer: 1. The equator

Question 22. Spot the wrong statement :

1. The acceleration due to gravity ‘g’ decreases if –
2. We go down from the surface of the earth towards its centre
3. We go up from the surface of the earth
4. We go from the equator towards the poles on the surface of the earth
5. The rotational velocity of the earth is increased

Answer: 3. We go from the equator towards the poles on the surface of the earth

Question 23. Choose the correct statement from the following : Weightlessness of an astronaut moving in a satellite is a situation of –

1. Zero g
2. No gravity
3. Zero mass
4. Free fall

Answer: 4. Free fall

Question 24. If the earth suddenly shrinks (without changing mass) to half of its present radius, the acceleration due to gravity will be –

1. g/2
2. 4g
3. g/4
4. 2g

Answer: 2. 4g

Question 25. The moon’s radius is 1/4 that of the earth and its mass is 1/80 times that of the earth. If g represents the acceleration due to gravity on the surface of the earth, that on the surface of the moon is –

1. g/4
2. g/5
3. g/6
4. g/8

Answer: 2. g/5

Question 26. The radius of the earth is around 6000 km. The weight of a body at a height of 6000 km from the earth’s surface becomes –

1. Half
2. One-fourth
3. One third
4. No change

Answer: 2. One-fourth

Question 27. At what height from the ground will the value of ‘g’ be the same as that in a 10 km deep mine below the surface of the earth –

1. 20 km
2. 10 km
3. 15 km
4. 5 km

Answer: 4. 5 km

Question 28. At what distance from the centre of the earth, the value of acceleration due to gravity g will be half that on the surface (R = Radius of earth)

1. 2R
2. R
3. 1.414 R
4. 0.414 R

Answer: 3. 1.414 R

Question 29. What will be the acceleration due to gravity at height h if h >> R. Where R is the radius of the earth and g is the acceleration due to gravity on the surface of the earth.

1. \(\frac{g}{\left(1+\frac{h}{R}\right)^2}\)
2. \(g\left(1-\frac{2 h}{R}\right)\)
3. \(\frac{g}{\left(1-\frac{h}{R}\right)^2}\)
4. \(g\left(1-\frac{h}{R}\right)\)

Answer: 1. \(\frac{g}{\left(1+\frac{h}{R}\right)^2}\)

Question 30. If the density of the earth is doubled keeping its radius constant then acceleration due to gravity will be (g = 9.8 m/s²)

1. 19.6 m/s²
2. 9.8 m/s²
3. 4.9 m/s²
4. 2.45 m/s²

Answer: 1. 19.6 m/s²

Question 31. The acceleration due to gravity at the pole and equator can be related as –

1. gp< ge
2. gp= ge= g
3. gp= ge< g
4. gp> ge

Answer: 4. gp> ge

Question 32. The depth at which the effective value of acceleration due to gravity is \(\frac{g}{4}\) is

1. R
2. \(\frac{3 R}{4}\)
3. \(\frac{R}{2}\)
4. \(\frac{R}{4}\)

Answer: 2. \(\frac{R}{2}\)

Question 33. Two bodies of mass 100 kg and 104 kg are lying one meter apart. At what distance from a 100 kg body will the intensity of the gravitational field be zero

1. \(\frac{1}{9} m\)
2. \(\frac{1}{10} m\)
3. \(\frac{1}{11} m\)
4. \(\frac{10}{11} \mathrm{~m}\)

Answer: 3. \(\frac{1}{11} m\)

Question 34. Figure shows a hemispherical shell having uniform mass density. The direction of gravitational field intensity at point P will be along:

1. a
2. b
3. c
4. d

Answer: 3. c

Question 35. Two bodies of mass 10² kg and 10³ kg are lying 1m apart. The gravitational potential at the mid-point of the line joining them is

1. 0
2. –1.47 Joule/kg
3. 1.47 Joule/kg
4. –1.47 × 10^-9 joule/kg

Answer: 4. –1.47 × 10^-9 joule/kg

Question 36. A simple pendulum has a period T₁ when on the earth’s surface, and T₂ when taken to a height R above the earth’s surface, where R is the radius of the earth. The value of T₂/T₁ is:

1. 1
2. \(\sqrt{2}\)
3. 4
4. 2

Answer: 4. 2

Question 37. Near earth time period of a satellite is 4 h. Find its time period at a distance 4R from the centre of earth:

1. 32 h
2. \(\left(\frac{1}{8^3 \sqrt{2}}\right) h\)
3. \(8^3 \sqrt{2} h\)
4. 16 h

Answer: 1. 32 h

Question 38. The radius of the orbit of a planet is two times that of the Earth. The time period of a planet is:

1. 4.2 T
2. 2.8 T
3. 5.6 T
4. 8.4 T

Answer: 2. 2.8 T

Question 39. In the case of earth:

1. The field is zero, both at the centre and infinity
2. The potential is zero, both at the centre and infinity
3. The potential is the same, both at centre and infinity but not zero
4. The potential is maximum at the centre

Answer: 1. Field is zero, both at the centre and infinity

NEET Physics Chapter 7 Gravitation MCQs and Answer Key

Question 40. What would be the angular speed of the earth, so that bodies lying on the equator may appear weightless? (g = 10m/s² and radius of earth = 6400 km)

1. 1.25 × 10^-3 rad/sec
2. 1.25 × 10^-2 rad/sec
3. 1.25 × 10^-4 rad/sec
4. 1.25 × 10^-1 rad/sec

Answer: 1. 1.25 × 10^-3 rad/sec

Question 41. The speed with which the earth has to rotate on its axis so that a person on the equator would weigh (3/5)th as much as present will be (Take the equatorial radius as 6400 km.)

1. 3.28 × 10^-4 rad/sec
2. 7.826 × 10^-4 rad/sec
3. 3.28 × 10^-3 rad/sec
4. 7.28 × 10^-3 rad/sec

Answer: 2. 7.826 × 10^-4 rad/sec

Question 42. A body of mass m is lifted up from the surface of the earth to a height three times the radius of the earth. The change in potential energy of the body is (g = gravity field at the surface of the earth)

1. mgR
2. \(\frac{3}{4} \mathrm{mgR}\)
3. \(\frac{1}{3} \mathrm{mgR}\)
4. \(\frac{2}{3} \mathrm{mgR}\)

Answer: 2. \(\frac{3}{4} \mathrm{mgR}\)

Question 43. The change in potential energy when a body of mass m is raised to a height n R from the earth’s surface is (R = Radius of earth)

1. mgR
2. nmgR
3. \(\mathrm{mgR} \frac{n^2}{n^2+1}\)
4. \(\mathrm{mgR} \frac{n}{n+1}\)

Answer: 4. \(\mathrm{mgR} \frac{n}{n+1}\)

Question 44. If the mass of the earth is M, the radius is R and the gravitational constant is G, then work done to take 1 kg mass from the earth’s surface to infinity will be –

1. \(\sqrt{\frac{G M}{2 R}}\)
2. \(\frac{G M}{R}\)
3. \(\sqrt{\frac{2 G M}{R}}\)
4. \(\frac{G M}{2 R}\)

Answer: 2. \(\frac{G M}{R}\)

Question 45. A rocket is launched with a velocity of 10 km/s. If the radius of the earth is R, then the maximum height attained by it will be

1. 2R
2. 3R
3. 4R
4. 5R

Answer: 3. 3R

Question 46. What is the intensity of the gravitational field at the centre of a spherical shell –

1. Gm/r²
2. g
3. Zero
4. None of these

Answer: 3. Zero

Question 47. The escape velocity of a body of 1 kg mass on a planet is 100 m/sec. The gravitational Potential energy of the body on the Planet is –

1. – 5000 J
2. – 1000 J
3. – 2400 J
4. 5000 J

Answer: 1. – 5000 J

Question 48. The kinetic energy needed to project a body of mass m from the earth’s surface (radius R) to infinity is –

1. mgR/2
2. 2 mgR
3. mgR
4. mgR/4

Answer: 3. mgR

Question 49. The escape velocity of a sphere of mass m from Earth having mass M and radius R is given by –

1. \(\sqrt{\frac{2 G M}{R}}\)
2. \(2 \sqrt{\frac{G M}{R}}\)
3. \(\sqrt{\frac{2 G M m}{R}}\)
4. \(\sqrt{\frac{G M}{R}}\)

Answer: 1. \(\sqrt{\frac{2 G M}{R}}\)

Question 50. If g is the acceleration due to gravity at the earth’s surface and r is the radius of the earth, the escape velocity for the body to escape out of the earth’s gravitational field is –

1. gr
2. \(\sqrt{2 g r}\)
3. g/r
4. r/g

Answer: 2. \(\sqrt{2 g r}\)

NEET Physics Class 11 Chapter 7 Gravitation Multiple Choice Questions and Answers

Question 51. For the moon to cease to remain the earth’s satellite, its orbital velocity has to increase by a factor of –

1. 2
2. \(\sqrt{2}\)
3. \(1 / \sqrt{2}\)
4. \(\sqrt{3}\)

Answer: 2. \(\sqrt{2}\)

Question 52. Escape velocity on a planet is ve. If the radius of the planet remains the same and the mass becomes 4 times, the escape velocity becomes –

1. 4v_e
2. 2v_e
3. v_e
4. v_e

Answer: 2. 2v_e

Question 53. How many times is the escape velocity (Ve), of orbital velocity (V0) for a satellite revolving near Earth –

1. \(\sqrt{2}\) times
2. 2 times
3. 3 times
4. 4 times

Answer: 1. \(\sqrt{2}\) times

Question 54. If the radius of a planet is R and its density is, the escape velocity from its surface will be –

1. \(v_e \propto R\)
2. \(\mathrm{v}_{\mathrm{e}} \propto \mathrm{R} \sqrt{p}\)
3. \(\mathrm{v}_{\mathrm{e}} \propto \frac{\sqrt{\rho}}{R}\)
4. \(\mathrm{v}_{\mathrm{e}} \propto \frac{1}{\sqrt{\rho R}}\)

Answer: 2. \(\mathrm{v}_{\mathrm{e}} \propto \mathrm{R} \sqrt{p}\)

Question 55. If V, R and g denote respectively the escape velocity from the surface of the earth radius of the earth, and acceleration due to gravity, then the correct equation is –

1. \(v=\sqrt{g R}\)
2. \(V=\sqrt{\frac{4}{3} g R^3}\)
3. \(\mathrm{V}=\mathrm{R} \sqrt{g}\)
4. \(V=\sqrt{2 g R}\)

Answer: 4. \(V=\sqrt{2 g R}\)

Question 56. If the radius of a planet is four times that of Earth and the value of g is the same for both, the escape velocity on the planet will be –

1. 11.2 km/s
2. 5.6 km/s
3. 22.4 km/s
4. None

Answer: 3. 22.4 km/s

Question 57. If the radius and acceleration due to gravity both are doubled, the escape velocity of the earth will become.

1. 11.2 km/s
2. 22.4 km/s
3. 5.6 km/s
4. 44.8 km/s

Answer: 2. 22.4 km/s

Question 58. If g is the acceleration due to gravity on the earth’s surface, the gain in P.E. of an object of mass m raised from the surface of the earth to a height of the radius R of the earth is

1. mgR
2. 2mgR
3. 12mgR
4. 14mgR

Answer: 3. 12mgR

Question 59. A missile is launched with a velocity less than the escape velocity. The sum of kinetic energy and potential energy will be

1. Positive
2. Negative
3. Negative or positive, uncertain
4. Zero

Answer: 2. Negative

Question 60. If v_e is escape velocity and v₀ is the orbital velocity of a satellite for orbit close to the earth’s surface, then these are related by :

1. \(\mathrm{v}_0=\sqrt{2} v_e\)
2. \(v_0=v_e\)
3. \(v_e=\sqrt{2 v_0}\)
4. \(v_e=\sqrt{2} v_0\)

Answer: 4. \(v_e=\sqrt{2} v_0\)

Question 61. An artificial satellite moving in a circular orbit around the earth has a total (kinetic + potential) energy E0. Its potential energy is :

1. − Eº
2. 1.5 Eº
3. 2 Eº
4. Eº

Answer: 3. 2 Eº

Question 62. The mass and radius of the earth and moon are M₁, R₁ and M₂, R₂ respectively. Their centres are d distance apart. With what velocity should a particle of mass m be projected from the midpoint of its centres so that it may escape out to infinity?

1. \(\sqrt{\frac{G\left(M_1+M_2\right)}{d}}\)
2. \(\sqrt{\frac{2 G\left(M_1+M_2\right)}{d}}\)
3. \(\sqrt{\frac{4 G\left(M_1+M_2\right)}{d}}\)
4. \(\sqrt{\frac{G M_1 M_2}{d}}\)

Answer: 3. \(\sqrt{\frac{4 G\left(M_1+M_2\right)}{d}}\)

Question 63. A satellite has to revolve around the earth in a circular orbit of radius 8 × 10³ km. The velocity of projection of the satellite in this orbit will be

1. 16 km/sec
2. 8 km/sec
3. 3 km/sec
4. 7.08 km/sec

Answer: 4. 7.08 km/sec

Question 64. The ratio of the radius of the earth to that of the moon is 10. The ratio of g an earth to the moon is 6. The ratio of the escape velocity from the Earth’s surface to that from the moon is approximately

1. 10
2. 8
3. 4
4. 2

Answer: 2. 8

Question 65. Acceleration due to gravity on a planet is 10 times the value on the Earth. Escape velocity for the planet and the earth are V_p and V_e respectively Assuming that the radii of the planet and the earth are the same, then

1. \(V_{\mathrm{P}}=10 \mathrm{~V}_{\mathrm{e}}\)
2. \(V_P=\sqrt{10} V_e\)
3. \(V_P=\frac{V_e}{\sqrt{10}}\)
4. \(V_P=\frac{V_e}{10}\)

Answer: 3. \(V_P=\frac{V_e}{\sqrt{10}}\)

Question 66. A space shuttle is launched in a circular orbit near the Earth’s surface. The additional velocity given to the space shuttle to get free from the influence of gravitational force will be

1. 1.52 km/s
2. 2.75 km/s
3. 3.28 km/s
4. 5.18 km/s

Answer: 3. 3.28 km/s

Question 67. A body of mass m is situated at a distance 4R_e above the earth’s surface, where R_e is the radius of the earth. How much minimum energy be given to the body so that it may escape

1. mgR_e
2. 2mgR_e
3. \(\frac{m g R_e}{5}\)
4. \(\frac{m g R_e}{16}\)

Answer: 3. \(\frac{m g R_e}{5}\)

Question 68. The potential energy of a body of mass 3kg on the surface of a planet is 54 joule. The escape velocity will be

1. 18m/s
2. 162 m/s
3. 36 m/s
4. 6 m/s

Answer: 4. 6 m/s

NEET Class 11 Gravitation Multiple Choice Questions

Question 69. The escape velocity from a planet is v₀. The escape velocity from a planet having twice the radius but the same density will be

1. 0.5 v₀
2. v₀
3. 2v₀
4. 4v₀

Answer: 3. 2v₀

Question 70. If the kinetic energy of a satellite orbiting around the earth is doubled then

1. The satellite will escape into space.
2. The satellite will fall down on the earth
3. The radius of its orbit will be doubled
4. The radius of its orbit will become half

Answer: 1. The satellite will escape into the space.

Question 71. The escape velocity from the earth does not depend upon

1. Mass of earth
2. Mass of the body
3. Radius of earth
4. Acceleration due to gravity

Answer: 2. Mass of the body

Question 72. There is no atmosphere on the moon because

1. It is near the earth
2. It is orbiting around the earth
3. There was no gas at all
4. The escape velocity of gas molecules is less than their root-mean-square velocity

Answer: 4. The escape velocity of gas molecules is less than their root-mean-square velocity

Question 73. The escape velocity is

1. 2gR
2. gR
3. \(\sqrt{g R}\)
4. \(\sqrt{2g R}\)

Answer: 4. \(\sqrt{2g R}\)

Question 74. A particle of mass m is taken through the gravitational field produced by a source S, from A to B, along the three paths as shown in the figure. If the work done along the paths 1, 2 and 3 is W₁, W₂ and W₃ respectively, then

1. W₁= W₂= W₃
2. W₂> W₃= W₂
3. W₃= W₂> W₁
4. W₁> W₂> W₃

Answer: 1. W₁= W₂= W₃

Question 75. The escape velocity of a particle of mass m varies as :

1. m²
2. m
3. m⁰
4. m^-1

Answer: 3. m⁰

Question 76. Acceleration due to gravity at the earth’s surface is g ms^-2. Find the effective value of gravity at a height of 32 km from sea level : (R_e= 6400 km) (R_e= 6400 km)

1. 0.5 g ms^-2
2. 0.99 g ms^-2
3. 1.01 g ms^-2
4. 0.90 g ms^-2

Answer: 2. 0.99 g ms^-2

Question 77. The radius of orbit of the satellite of earth is R. Its kinetic energy is proportional to :

1. \(\frac{1}{R}\)
2. \(\frac{1}{\sqrt{R}}\)
3. R
4. \(\frac{1}{R^{3 / 2}}\)

Answer: 1. \(\frac{1}{R}\)

Question 78. A cosmonaut is orbiting earth in a spacecraft at an altitude h = 630 km with a speed of 8 km/s. If the radius of the earth is 6400 km, the acceleration of the cosmonaut is

1. 9.10 m/s²
2. 9.80 m/s²
3. 10.0 m/s²
4. 9.88 m/s²

Answer: 1. 9.10 m/s²

Question 79. A very very large number of particles of the same mass m are kept at horizontal distances of 1m, 2m, 4m, 8m and so on from (0,0) point. The total gravitational potential at this point is (addition of G.P. of infinite terms = \(\frac{a}{1-r}\) where a = first term, r = common ratio) :

1. – 8G m
2. – 3G m
3. – 4G m
4. – 2G m

Answer: 4. – 2G m

Question 80. A body starts from rest at a point, distance R₀ from the centre of the earth of mass M, radius R. The velocity acquired by the body when it reaches the surface of the earth will be

1. \(\mathrm{GM}\left(\frac{1}{R}-\frac{1}{R_0}\right)\)
2. \(2 \mathrm{GM}\left(\frac{1}{R}-\frac{1}{R_0}\right)\)
3. \(\sqrt{2 G M\left(\frac{1}{R}-\frac{1}{R_0}\right)}\)
4. \(2 \mathrm{GM} \sqrt{\left(\frac{1}{R}-\frac{1}{R_0}\right)}\)

Answer: 3. \(\sqrt{2 G M\left(\frac{1}{R}-\frac{1}{R_0}\right)}\)

Question 81. The relation between the escape velocity from the earth and the velocity of a satellite orbiting near the earth’s surface is

1. v_e = 3v
2. v_e= v
3. v_e= 2v
4. v_e= v/2

Answer: 2. v_e= v

Question 82. A body attains a height equal to the radius of the earth. The velocity of the body with which it was projected is :

1. \(\sqrt{\frac{G M}{R}}\)
2. \(\sqrt{\frac{2 G M}{R}}\)
3. \(\sqrt{\frac{5}{4} \frac{G M}{R}}\)
4. \(\sqrt{\frac{3 G M}{R}}\)

Answer: 1. \(\sqrt{\frac{G M}{R}}\)

Question 83. A satellite of mass m is circulating around the earth with constant angular velocity. If the radius of the orbit is R₀ and the mass of the earth is M, the angular momentum about the centre of the earth is

1. \(M \sqrt{G M R_0}\)
2. \(M \sqrt{G m R_0}\)
3. \(M \sqrt{\frac{G M}{R_0}}\)
4. \(M \sqrt{\frac{G M}{R_0}}\)

Answer: 1. \(M \sqrt{G M R_0}\)

Question 84. Which of the following quantities is conserved for a satellite revolving around the earth in a particular orbit?

1. Angular velocity
2. Force
3. Angular momentum
4. Velocity

Answer: 3. Angular momentum

Question 85. The distance of Neptune and Saturn from sun are nearly 10¹³ and 10¹² meters respectively. Assuming that they move in circular orbits, their periodic times will be in the ratio –

1. \(\sqrt{10}\)
2. 100
3. \(10 \sqrt{10}\)
4. \(1 / \sqrt{10}\)

Answer: 3. \(10 \sqrt{10}\)

Question 86. The period of a satellite in a circular orbit of radius R is T, and the period of another satellite in a circular orbit of radius 4R is –

1. 4T
2. T/4
3. 8T
4. T/8

Answer: 3. 8T

Question 87. If a body describes a circular motion under an inverse square field, the time taken to complete one revolution T is related to the radius of the circular orbit as –

1. T ∝ r
2. T ∝ r²
3. T² ∝ r³
4. T ∝ r⁴

Answer: 3. T² ∝ r³

Question 88. The escape velocity of a sphere of mass m from Earth having mass M and radius R is given by –

1. \(\sqrt{\frac{2 G M}{R}}\)
2. \(2 \sqrt{\frac{G M}{R}}\)
3. \(\sqrt{\frac{2 G M m}{R}}\)
4. \(\sqrt{\frac{G M}{R}}\)

Answer: 1. \(\sqrt{\frac{2 G M}{R}}\)

Question 89. The escape velocity from the earth is about 11 km/second. The escape velocity from a planet having twice the radius and the same mean density as the Earth is –

1. 22km/sec
2. 11 km/sec
3. 5.5 km/sec
4. 15.5 km/sec

Answer: 1. 22km/sec

Question 90. A satellite which is geostationary in a particular orbit is taken to another orbit. Its distance from the centre of the earth in the new orbit is 2 times that of the earlier orbit. The time period in the second orbit is –

1. 4.8 hours
2. \(48 \sqrt{2}\) hours
3. 24 hrs
4. Infinite

Answer: 2. \(48 \sqrt{2}\) hours

Question 91. Two satellites A and B go around planet P in circular orbits having radial 4R and R respectively. If the speed of the satellite A is 3V, the speed of the satellite B will be

1. 12 V
2. 6 V
3. 4/3 V
4. 3/2 V

Answer: 2. 6 V

Question 92. The escape velocity for a rocket from earth is 11.2 km/sec. Its value on a planet where the acceleration due to gravity is double that on the earth and the diameter of the planet is twice that of the earth will be in km/sec-

1. 11.2
2. 5.6
3. 22.4
4. 53.6

Answer: 3. 22.4

Question 93. A satellite revolves around the earth in an elliptical orbit. Its speed

1. Is the same at all points in the orbit
2. Is greatest when it is closest to the earth
3. Is greatest when it is farthest from the earth
4. Goes on increasing or decreasing continuously depending upon the mass of the satellite

Answer: 2. Is greatest when it is closest to the earth

Question 94. Time period of revolution of a satellite around a planet of radius R is T. The Period of revolution around another planet, whose radius is 3R but has the same density is –

1. \(\frac{T}{3 \sqrt{3}}\)
2. 3T
3. 9T
4. \(3 \sqrt{3} T\)

Answer: 1. \(\frac{T}{3 \sqrt{3}}\)

Question 95. If Veand V₀ represent the escape velocity and orbital velocity of a satellite corresponding to a circular orbit of radius R, then –

1. \(V_e=V_0\)
2. \(\sqrt{2} V_0=V_e\)
3. \(V_e=\frac{1}{\sqrt{2}} V_o\)
4. None of these

Answer: 2. \(\sqrt{2} V_0=V_e\)

Question 96. A spherical planet far out in space has a mass of M₀ and a diameter D₀. A particle will experience acceleration due to gravity which is equal to

1. GM₀/D_0²
2. 2mGM₀/D_0²
3. 4GM₀/D_0²
4. GmM₀/D_0²

Answer: 3.4GM₀/D_0²

Gravitation NEET Class 11 MCQs with Detailed Solutions

Question 97. A satellite can be in a geostationary orbit around a planet at a distance r from the centre of the planet. If the angular velocity of the planet about its axis doubles, a satellite can now be in a geostationary orbit around the planet if its distance from the centre of the planet is

1. \(\frac{r}{2}\)
2. \(\frac{r}{2 \sqrt{2}}\)
3. \(\frac{r}{(4)^{1 / 3}}\)
4. \(\frac{r}{(2)^{1 / 3}}\)

Answer: 3. \(\frac{r}{(4)^{1 / 3}}\)

Question 98. Consider a satellite going around the earth in an orbit. Which of the following statements is wrong –

1. It is a freely falling body
2. It suffers no acceleration
3. It is moving at a constant speed
4. Its angular momentum remains constant

Answer: 2. It suffers no acceleration

Question 99. The period of a satellite in a circular orbit around a planet is independent of –

1. The mass of the planet
2. The radius of the planet
3. The mass of the satellite
4. All the three parameters (1), (2) and (3)

Answer: 3. The mass of the satellite

Question 100. A small satellite is revolving near the earth’s surface. Its orbital velocity will be nearly.

1. 8 km/sec
2. 11.2 km/sec
3. 4 km/sec
4. 6 km/sec

Answer: 1. 8 km/sec

Question 101. A satellite revolves around the earth in an elliptical orbit. Its speed.

1. Is the same at all points in the orbit
2. Is greatest when it is closest to the earth
3. Is greatest when it is farthest from the earth
4. Goes on increasing or decreasing continuously depending upon the mass of the satellite

Answer: 2. Is greatest when it is closest to the earth

Question 102. If the height of a satellite from the earth is negligible in comparison to the radius of the earth R, the orbital velocity of the satellite is –

1. gR
2. gR/2
3. \(\sqrt{g / R}\)
4. \(\sqrt{g R}\)

Answer: 4. \(\sqrt{g R}\)

Question 103. Orbital velocity of an artificial satellite does not depend upon –

1. Mass of the earth
2. Mass of the satellite
3. Radius of the earth
4. Acceleration due to gravity

Answer: 2. Mass of the satellite

Question 104. The time period of a geostationary satellite is –

1. 24 hours
2. 12 hours
3. 365 days
4. One month

Answer: 1. 24 hours

Question 105. Which one of the following statements regarding artificial satellites of the earth is incorrect –

1. The orbital velocity depends on the mass of the satellite
2. A minimum velocity of 8 km/sec is required by a satellite to orbit quite close to the earth
3. The period of revolution is large if the radius of its orbit is large
4. The height of a geostationary satellite is about 36000 km from earth

Answer: 1. The orbital velocity depends on the mass of the satellite

Question 106. Two identical satellites are at R and 7R away from the earth’s surface, the wrong statement is (R = Radius of the earth)

1. The ratio of total energy will be 4
2. The ratio of kinetic energies will be 4
3. The ratio of potential energies will be 4
4. The ratio of total energy will be 4 but the ratio of potential and kinetic energies will be 2

Answer: 4. Ratio of total energy will be 4 but the ratio of potential and kinetic energies will be 2

Question 107. For a satellite escape velocity is 11 km/s. If the satellite is launched at an angle of 60º with the vertical, then the escape velocity will be –

1. 11 km/s
2. \(11 \sqrt{3} \mathrm{~km} / \mathrm{s}\)
3. \(\frac{11}{\sqrt{3}} \mathrm{~km} / \mathrm{s}\)
4. 33 km/s

Answer: 1. 11 km/s

Question 108. The distance of a geo-stationary satellite from the centre of the earth (Radius R = 6400 km) is nearest to –

1. 5 R
2. 7 R
3. 10 R
4. 18 R

Answer: 2. 7 R

Question 109. Periodic time of a satellite revolving above Earth’s surface at a height equal to R, radius of Earth, is [g is acceleration due to gravity at Earth’s surface]

1. \(2 \pi \sqrt{\frac{2 R}{g}}\)
2. \(4 \sqrt{2} \pi \sqrt{\frac{R}{g}}\)
3. \(2 \pi \sqrt{\frac{R}{g}}\)
4. \(8 \pi \sqrt{\frac{R}{g}}\)

Answer: 2. \(4 \sqrt{2} \pi \sqrt{\frac{R}{g}}\)

Question 110. Given the radius of Earth ‘R’ and length of a day ‘T’ the height of a geostationary satellite is [G-Gravitational constant. M-Mass of Earth]

1. +R
2. – R
3. – R
4. None

Answer: 3. – R

Question 111. The distance of a geostationary satellite from the surface of the earth radius (Re= 6400 km) in terms of Re is –

1. 13.76 R_e
2. 10.76 R_e
3. 5.56 R_e
4. 2.56 R_e

Answer: 3. 5.56 R_e

Question 112. The orbital velocity of a planet revolving close to the earth’s surface is –

1. \(\sqrt{2 g R}\)
2. \(\sqrt{g R}\)
3. \(\sqrt{\frac{2 g}{R}}\)
4. \(\sqrt{\frac{g}{R}}\)

Answer: 2. \(\sqrt{g R}\)

Question 113. A satellite moves around the earth in a circular orbit of radius r with speed v. If the mass of the satellite is M, its total energy is –

1. \(-\frac{1}{2} \mathrm{Mv}^2\)
2. \(\frac{1}{2} M v^2\)
3. \(\frac{3}{2} M v^2\)
4. Mv²

Answer: 1. \(-\frac{1}{2} \mathrm{Mv}^2\)

Question 114. If a satellite is shifted towards the earth. The time period of the satellite will be –

1. Increase
2. Decrease
3. Unchanged
4. Nothing can be said

Answer: 2. Decrease

Question 115. Two satellites A and B go around a planet in circular orbits having radii 4R and R, respectively. If the speed of satellite A is 3v, then the speed of satellite B is –

1. \(\frac{3 v}{2}\)
2. \(\frac{4 v}{2}\)
3. 6v
4. 12v

Answer: 3. 6v

Question 116. If gravity field due to a point mass follows \(\mathrm{g} \propto \frac{1}{r^3}\) instead of \(\frac{1}{r^2}\), then the relation between time period of a satellite near earth’s surface and radius of its orbit r will be –

1. T² ∝ r³
2. T ∝ r²
3. T² ∝ r
4. T ∝ r

Answer: 2. T ∝ r²

Question 117. A satellite appears to be at rest when seen from the equator. Its height from the earth’s surface is nearly

1. 35800km
2. 358000 km
3. 6400km
4. Such a satellite cannot exist

Answer: 1. 35800km

Question 118. A body is dropped by a satellite in its geostationary orbit

1. It will burn on entering the atmosphere
2. It will remain in the same place with respect to the earth
3. It will reach the earth in 24 hours
4. It will perform uncertain motion

Answer: 2. It will remain in the same place with respect to the earth

Question 119. A satellite of Earth can move only in those orbits whose plane coincides with

1. The plane of a great circle of the earth
2. The plane passing through the poles of the earth
3. The plane of a circle at any latitude on earth
4. None of these

Answer: 1. The plane of a great circle of the earth

Question 120. A satellite launching station should be

1. Near the equatorial region
2. Near the polar region
3. On the polar axis
4. All locations are equally good

Answer: 1. Near the equatorial region

Question 121. The minimum number of satellites needed to be placed at the surface of the earth for worldwide communication between any two locations is –

1. 6
2. 4
3. 3
4. 5

Answer: 3. 3

NEET Physics Gravitation Chapter 7 MCQs and Solutions

Question 122. A geostationary satellite orbits around the earth in a circular orbit with a radius of 36000 km. Then, the time period of a spy satellite orbiting a few hundred kilometres above the earth’s surface (R_Earth = 6400 km) will approximately be :

1. 1/2 hr
2. 1 hr
3. 2 hr
4. 4 hr

Answer: 3. 2 hr

Question 123. A satellite is moving with a constant speed ‘V’ in a circular orbit about the earth. An object of mass ‘m’ is ejected from the satellite such that it just escapes from the gravitational pull of the earth. At the time of its ejection, the kinetic energy of the object is

1. \(\frac{1}{2} m V^2\)
2. mV²
3. \(\frac{3}{2} m V^2\)
4. 2mV²

Answer: 2. mV²

Question 124. Two satellites of earth, S₁ and S₂ are moving in the same orbit. The mass of S₁ is four times the mass of S₂. Which one of the following statements is true:

1. The time period of S₁ is four times that of S₂
2. The potential energies of the earth and satellite in the two cases are equal
3. S₁ and S₂ are moving at the same speed
4. The kinetic energies of the two satellites are equal

Answer: 3. S₁ and S₂ are moving at the same speed

Question 125. The orbital speed of a satellite revolving near the earth is :

1. \(\sqrt{2 g R}\)
2. \(\sqrt{g R}\)
3. \(\sqrt{g / R}\)
4. \(\sqrt{2 g / R}\)

Answer: 2. \(\sqrt{g R}\)

Question 126. If the radius of the earth is decreased by 1% and mass remains constant, then the acceleration due to gravity

1. Decrease by 2%
2. Decrease by 1%
3. Increase by 1%
4. Increase by 2%

Answer: 4. Increase by 2%

Question 127. The escape velocity for a rocket is 11.2 km/s. If it is taken to a planet where the radius and acceleration due to gravity are double that of earth, then the escape velocity will be :

1. 5.6 m/s
2. 11.2 m/s
3. 22.4 km/s
4. 44.2 m/s

Answer: 3. 22.4 km/s

Question 128. Suppose the radius of the moon’s orbit around the earth is doubled. Its period around the earth will become:

1. 1/2 times
2. \(\sqrt{2}\) times
3. 22/3 times
4. 23/2 times

Answer: 4. 23/2 times

Question 129. In the case of an orbiting satellite if the radius of the orbit is decreased :

1. Its Kinetic Energy decreases
2. Its Potential Energy increase
3. Its Mechanical Energy decreases
4. Its speed decreases

Answer: 3. Its Mechanical Energy decreases

Question 130. A satellite of the earth is revolving in a circular orbit with a uniform speed v. If the gravitational force suddenly disappears, the satellite will

1. Continue to move with velocity v along the original orbit
2. Move with a velocity v, tangentially to the original orbit
3. Fall down with increasing velocity
4. Ultimately come to rest somewhere in the original orbit

Answer: 2. Move with a velocity v, tangentially to the original orbit

Question 131. The time period of a satellite of earth is 5 hours. If the separation between the earth and the satellite is increased to 4 times the previous value, the new time period becomes

1. 10 hour
2. 80 hour
3. 40 hour
4. 20 hour

Answer: 3. 40 hour

NEET Class 11 Physics Gravitation Multiple Choice Questions and Solutions

Question 132. The escape velocity for a body projected vertically upwards from the surface of the earth is 11 km/s. If the body is projected at an angle of 45º with the vertical, the escape velocity will be :

1. \(11 \sqrt{2} \mathrm{~km} / \mathrm{s}\)
2. 22 km/s
3. 11 km/s
4. \(11 / \sqrt{2} \mathrm{~m} / \mathrm{s}\) m/s

Answer: 3. 11 km/s

Question 133. A satellite of mass m revolves around the earth of radius R at a height x from its surface. If g is the acceleration due to gravity on the surface of the earth, the orbital speed of the satellite is :

1. gx
2. \(\frac{g R}{R-x}\)
3. \(\frac{g R^2}{R+x}\)
4. \(\left(\frac{g R^2}{R+x}\right)^{1 / 2}\)

Answer: 4. \(\frac{g R}{R-x}\)

Question 134. The time period of an earth satellite in a circular orbit is independent of :

1. The mass of the satellite
2. The radius of its orbit
3. Both the mass and radius of the orbit
4. Neither the mass of the satellite nor the radius of its orbit

Answer: 1. The mass of the satellite

Question 135. If g is the acceleration due to gravity on the earth’s surface, the gain in the potential energy of an object of mass m raised from the surface of the earth to a height equal to the radius R of the earth, is :

1. 2mgR
2. \(\frac{1}{2} m g R\)
3. \(\frac{1}{4} m g R\)
4. mgR

Answer: 2. \(\frac{1}{2} m g R\)

Question 136. The change in the value of ‘g’ at a height ‘h’ above the surface of the earth is the same as at a depth ‘d’ below the surface of the earth. When both ‘d’ and ‘h’ are much smaller than the radius of the earth, then, which one of the following is correct?

1. \(\mathrm{d}=\frac{h}{2}\)
2. \(\mathrm{d}=\frac{3 h}{2}\)
3. d = 2h
4. d = h

Answer: 3. d = 2h

Question 137. A particle of mass 10 kg is kept on the surface of a uniform sphere of mass 100 kg and radius 10 cm. Find the work to be done against the gravitational force between them, to take the particle far away from the sphere (you may take G = 6.67 × 10^-11 Nm²/kg²);

1. 13.34 × 10^-10 J
2. 3.33 × 10^-10 J
3. 6.67 × 10^-9 J
4. 6.67 × 10^-7 J

Answer: 4. 6.67 × 10^-7 J

Question 138. If g_E and g_m are the accelerations due to gravity on the surfaces of the earth and the moon respectively and if Millikan’s oil drop experiment could be performed on the two surfaces, one will find the ratio

1. 1
2. 0
3. g_E/g_M
4. g_M/g_E

Answer: 1. 1

Question 139. A planet in a distant solar system is 10 times more massive than the earth and its radius is 10 times smaller. Given that the escape velocity from the earth is 11 km s^-1, the escape velocity from the surface of the planet would be

1. 11 km s^-1
2. 110 km s^-1
3. 0.11 km s^-1
4. 1.1 km s^-1

Answer: 2. 110 km s^-1

Question 140. The distance of neptune and saturn from the sun is nearly 10¹³ and 10¹² meters respectively. Assuming that they move in circular orbits, their periodic times will be in the ratio –

1. \(\sqrt{10}\)
2. 100
3. 10
4. 1/10

Answer: 3. 10

Question 141. The period of a satellite in a circular orbit of eradius R is T, and the period of another satellite in a circular orbit of radius 4R is.

1. 4T
2. T/4
3. 8T
4. T/8

Answer: 3. 8T

Question 142. Two planets move around the sun. The periodic times and the mean radii of the orbits are T₁, T₂ and r₁, r₂ respectively. The ratio T₁/ T₂ is equal to –

1. (r₁/ r₂)^1/2
2. r₁/ r₂
3. (r₁/ r₂)²
4. (r₁/ r₂)^3/2

Answer: 4. (r₁/ r₂)^3/2

Question 143. The rotation period of an earth satellite close to the surface of the earth is 83 minutes. The time period of another earth satellite in an orbit at a distance of three earth radii from its surface will be –

1. 83 minute
2. 83 × \(\sqrt{8}\) minutes
3. 664 minutes
4. 249 minutes

Answer: 3. 664 minutes

Question 144. A satellite of mass m is circulating around the earth with constant angular velocity. If the radius of the orbit is R₀ and the mass of the earth is M, the angular momentum about the centre of the earth is –

1. \(\mathrm{m} \sqrt{G M R_0}\)
2. \(\mathrm{M} \sqrt{G M R_0}\)
3. \(\mathrm{m} \sqrt{\frac{G M}{R_0}}\)
4. \(\mathrm{M} \sqrt{\frac{G M}{R_0}}\)

Answer: 1. \(\mathrm{m} \sqrt{G M R_0}\)

Question 145. A planet revolves around the sun whose mean distance is 1.588 times the mean distance between the earth and the sun. The revolution time of the planet will be –

1. 1.25 years
2. 1.59 years
3. 0.89 years
4. 2 years

Answer: 4. 2 years

Question 146. If the mass of a satellite is doubled and the time period remains constant the ratio of orbit in the two cases will be –

1. 1: 2
2. 1: 1
3. 1 : 3
4. None of these

Answer: 2. 1:1

Question 147. The earth revolves around the sun in one year. If the distance between them becomes double, the new period of revolution will be –

1. 1/2 years
2. \(2 \sqrt{2}\) years
3. 4 years
4. 8 years

Answer: 2. \(2 \sqrt{2}\) years

Question 148. A body revolved around the sun 27 times faster than the earth what is the ratio of their radii

1. 1/3
2. 1/9
3. 1/27
4. 1/4

Answer: 2. 1/9

Question 149. The orbital angular momentum of a satellite revolving at a distance r from the centre is L. If the distance is increased to 16r, then the new angular momentum will be –

1. 16 L
2. 64 L
3. \(\frac{L}{4}\)
4. 4 L

Answer: 4. 4 L

Question 150. The ratio of the distance of two planets from the sun is 1.38. The ratio of their period of revolution around the sun is –

1. 1.38
2. 1.38^3/2
3. 1.38^1/2
4. 1.38³

Answer: 2. 1.38^3/2

Question 151. Kepler’s second law (law of areas) is nothing but a statement of –

1. Work energy theorem
2. Conservation of linear momentum
3. Conservation of angular momentum
4. Conservation of energy

Answer: 3. Conservation of angular momentum

Question 152. In an elliptical orbit under gravitational force, in general.

1. Tangential velocity is constant
2. Angular velocity is constant
3. Radial velocity is constant
4. Areal velocity is constant

Answer: 4. Areal velocity is constant

Question 153. What does not change in the field of central force?

1. Potential energy
2. Kinetic energy
3. Linear momentum
4. Angular momentum

Answer: 4. Angular momentum

Question 154. A planet is moving in an elliptic orbit. If T, V, E, L stand respectively for their kinetic energy, gravitational potential energy, total energy and magnitude of angular momentum about the centre of force, which of the following statements is correct

1. T is conserved
2. V is always positive
3. E is always negative
4. L is conserved but the direction of the vector changes continuously

Answer: 3. E is always negative

Question 155. Three identical stars of mass M are located at the vertices of an equilateral triangle with side L. The speed at which they will move if they all revolve under the influence of one another’s gravitational force in a circular orbit circumscribing the triangle while still preserving the equilateral triangle :

1. \(\sqrt{\frac{2 G M}{L}}\)
2. \(\sqrt{\frac{G M}{L}}\)
3. \(2 \sqrt{\frac{G M}{L}}\)
4. Not possible at all

Answer: 2. \(\sqrt{\frac{G M}{L}}\)

Question 156. Periodic-time of a satellite revolving very near to the surface of the earth is – (ρ is the density of the earth)

1. Proportional to \(\frac{1}{\rho}\)
2. Proportional to \(\frac{1}{\sqrt{\rho}}\)
3. Proportional ρ
4. Does not depend on ρ.

Answer: 2. Proportional to \(\frac{1}{\sqrt{\rho}}\)

Question 157. A satellite is moving around the earth. In order to make it move to infinity, its velocity must be increased by

1. 20%
2. It is impossible to do so
3. 82.8%
4. 41.4%

Answer: 4. 41.4%

Question 158. If the radius of the earth is to decrease by 4% and its density remains the same, then its escape velocity will

1. Remain same
2. Increase by 4%
3. Decrease by 4%
4. Increase by 2%

Answer: 3. Decrease by 4%

NEET Class 11 Chapter 7 Gravitation Practice MCQs with Answers

Question 159. An earth satellite is moved from one stable circular orbit to another higher stable circular orbit. Which one of the following quantities increases for the satellite as a result of this change

1. Gravitational force
2. Gravitational potential energy
3. Centripetal acceleration
4. Linear orbital speed

Answer: 2. Gravitational potential energy

Question 160. The relay satellite transmits the television programme continuously from one part of the world to another because its

1. A period is greater than the period of rotation of the earth
2. Period is less than the period of rotation of the earth about its axis
3. Period has no relation with the period of the earth about its axis
4. Period is equal to the period of rotation of the earth about its axis

Answer: 4. Period is equal to the period of rotation of the earth about its axis

Question 161. If the universal constant of gravitation were decreasing uniformly with time, then a satellite in orbit would still maintain its

1. Radius
2. Tangential speed
3. Angular momentum
4. Period of revolution

Answer: 3. Angular momentum

Question 162. A satellite S is moving in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth :

1. The acceleration of S is always directed towards the centre of the earth
2. The angular momentum of S about the centre of the earth changes in direction, but its magnitude remains constant
3. The total mechanical energy of S varies periodically with time
4. The linear momentum of S remains constant in magnitude.

Answer: 1. The acceleration of S is always directed towards the centre of the earth

Question 163. The moon revolves around the Earth 13 times in one year. If the ratio of sun-earth distance to earth-moon distance is 392, then the ratio of masses of sun and earth will be

1. 3.56 × 10⁵
2. 3.56 × 10⁶
3. 3.56 × 10⁷
4. 3.56 × 10⁸

Answer: 1. 3.56 × 10⁵

Question 164. The earth revolves around the sun in an elliptical orbit. If \(\frac{O A}{O B}\)= x, the ratio of speeds of earth at B and A will be

1. x
2. \(\sqrt{x}\)
3. x2
4. \(x \sqrt{x}\)

Answer: 1. x

Question 165. The time period of a satellite of earth is 5 h. If the separation between the earth and the satellite is increased to 4 times the previous value, the new time period will become

1. 10 h
2. 80 h
3. 40 h
4. 20 h

Answer: 3. 40 h

Question 166. If two spheres of the same masses and radius are brought in contact, then the force of attraction between them will be proportional to (for a given density ρ) :

1. r²
2. r³
3. r⁶
4. r⁴

Answer: 4. r⁴

Question 167. Assume the earth to be a sphere of radius R. If g is the acceleration due to gravity at any point on the earth’s surface, the mass of the earth is :

1. \(\frac{g R}{G}\)
2. \(\frac{g^2 R^2}{G}\)
3. \(\frac{g R^2}{G}\)
4. \(\frac{g^2 R}{G}\)

Answer: 3. \(\frac{g R^2}{G}\)

Question 168. Energy required to transfer a 400 kg satellite in a circular orbit of radius 2 R to a circular orbit of radius 4 R, where R is the radius of the earth. [Given g = 9.8 ms^-2, R = 6.4 × 10⁶ m]

1. 1.65 × 10⁹ J
2. 3.13 × 10⁹ J
3. 6.26 × 10⁹ H
4. 4.80 × 10⁹ J

Answer: 2. 3.13 × 10⁹ J

Question 169. Suppose the gravitational force varies inversely as the 4th power of the distance. If a satellite describes a circular orbit of radius R under the influence of this force, then the time period T of the orbit is proportional to

1. R^3/2
2. R^5/2
3. R²
4. R^7/2

Answer: 2. R^5/2

Question 170. A double star system consists of two stars A and B which have time periods T_A and T_B. Radius R_A and R_B and mass M_A and M_B. Choose the correct option.

1. If T_A> T_B then R_A> R_B
2. If T_A> T_B then M_A> M_B
3. \(\left(\frac{T_A}{T_B}\right)^2=\left(\frac{R_A}{R_B}\right)^3\)
4. T_A = T_B

Answer: 4. T_A = T_B

Question 171. Mass M is uniformly distributed only on the curved surface of a thin hemispherical shell. A, B and C are three points on the circular base of a hemisphere, such that A is the centre. Let the gravitational potential at points A, B and C be V_A, V_B, V_C respectively. Then

1. V_A> V_B>V_C
2. V_C> V_B>V_A
3. V_B>V_A and V_B> V_C
4. V_A= V_B=V_C

Answer: 4. V_A= V_B=V_C

Question 172. The figure shows the elliptical orbit of a planet m about the sun S. The shaded area SCD is twice the shaded area SAB. If t1is the time for the planet to move from C to D and t₂ is the time to move from A to B, then:

1. t₁> t₂
2. t₁= 4t₂
3. t₁= 2t₂
4. t₁= t₂

Answer: 3. t₁= 2t₂

Question 173. A particle of mass M is situated at the centre of a spherical shell of the same mass and radius a. The gravitational potential at a point situated at \(\frac{a}{2}\) distance from the centre, will be

1. \(-\frac{3 G M}{a}\)
2. \(-\frac{2 G M}{a}\)
3. \(-\frac{G M}{a}\)
4. \(-\frac{4 G M}{a}\)

Answer: 1. \(-\frac{3 G M}{a}\)

Question 174. The additional kinetic energy to be provided to a satellite of mass m revolving around a planet of mass M, to transfer it from a circular orbit of radius R₁ to another of radius R₂(R₂> R₁) is

1. \(G m M\left(\frac{1}{R_1^2}-\frac{1}{R_2^2}\right)\)
2. \({GmM}\left(\frac{1}{R_1}-\frac{1}{R_2}\right)\)
3. \(-\frac{G M}{a}\)
4. \(-\frac{4 G M}{a}\)

Answer: 4. \(-\frac{4 G M}{a}\)

Question 175. The radii of circular orbits of two satellites A and B of the earth, are 4R and R, respectively. If the speed of satellite A is 3V, then the speed of satellite B will be

1. \(\frac{3 V}{4}\)
2. 6V
3. 12 V
4. \(\frac{3 V}{2}\)

Answer: 2. 6V

Question 176. The dependence of acceleration due to gravity g on the distance r from the centre of the earth, assumed to be a sphere of radius R of uniform density is as shown in the figures below. The correct figure is.

Answer: 4

Question 177. A planet moving along an elliptical orbit is closest to the sun at a distance r₁ and farthest away at a distance of r₂. If v₁ and v₂ are the linear velocities at these points respectively, then the ratio \(\frac{v_1}{v_2}\) is:

1. (r₁/r₂)²
2. r₂/r₁
3. (r₂/r₁)²
4. r₁/r₂

Answer: 2. r₂/r₁

Question 178. A body projected vertically from the Earth reaches a height equal to the earth’s radius before returning to the earth. The power exerted by the gravitational force is greatest :

1. At the highest position of the body
2. At the instant just before the body hits the earth
3. It remains constant all through
4. At the instant just after the body is projected

Answer: 2. At the instant just before the body hits the earth

Question 179. A particle of mass m is thrown upwards from the surface of the earth, with a velocity u. The mass and the radius of the earth are, respectively, M and R. G is gravitational constant and g is acceleration due to gravity on the surface of the earth. The minimum value of u so that the particle does not return back to earth, is :

1. \(\sqrt{\frac{2 G M}{R}}\)
2. \(\sqrt{\frac{2 G M}{R^2}}\)
3. \(\sqrt{2 g R^2}\)
4. \(\sqrt{\frac{2 G M}{R^2}}\)

Answer: 1. \(\sqrt{\frac{2 G M}{R}}\)

Question 180. A particle of mass M is situated at the centre of a spherical shell of mass and radius a. The magnitude of the gravitational potential at a point situated at a/2 distance from the centre will be:

1. \(\frac{2 G M}{a}\)
2. \(\frac{3 G M}{a}\)
3. \(\frac{4 G M}{a}\)
4. \(\frac{G M}{a}\)

Answer: 2. \(\frac{3 G M}{a}\)

Question 181. Which one of the following plots represents the variation of gravitational field on a particle with distance r due to a thin spherical shell of radius R ? (r is measured from the centre of the spherical shell)

Answer: 2

Question 182. The height at which the weight of a body becomes 1/16th, its weight on the surface of the earth (radius R), is :

1. 5R
2. 15R
3. 3R
4. 4R

Answer: 3. 3R

Question 183. A spherical planet has a mass MP and diameter DP. A particle of mass m falling freely near the surface of this planet will experience an acceleration due to gravity, equal to :

1. 4GMP/DP²
2. GMPm/DP²
3. GMP/DP²
4. 4GMPm/DP²

Answer: 1. 4GMP/DP²

Question 184. A geostationary satellite is orbiting the earth at a height of 5R above the surface of the earth, R is the radius of the earth. The time period of another satellite in hours at a height of 2R from the surface of the earth is :

1. 5
2. 10
3. \(6 \sqrt{2}\)
4. \(\frac{6}{\sqrt{2}}\)

Answer: 3. \(6 \sqrt{2}\)

Gravitation NEET Physics MCQs for Class 11 with Correct Answers

Question 185. A body of mass ‘m’ is taken from the earth’s surface to a height equal to twice the radius (R) of the earth. The change in potential energy of the body will be:

1. \(\frac{2}{3} m g R\)
2. 3mgR
3. \(\frac{1}{3} m g R\)
4. mg2R

Answer: 1. \(\frac{2}{3} m g R\)

Question 186. Infinite number of bodies, each of mass 2 kg are situated on the x-axis at distances 1m, 2m, 4m, 8m, …….. respectively, from the origin. The resulting gravitational potential due to this system at the origin will be :

1. \(-\frac{8}{3} G\)
2. \(-\frac{4}{3} G\)
3. –4G
4. – G

Answer: 3. –4G

Question 187. A block hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass = 5.98×10²⁴ kg) have to be compressed to be a black hole?

1. 10^-9 m
2. 10^-6 m
3. 10^-2 m
4. 100 m

Answer: 3. 10^-2 m

Question 188. Dependence of intensity of gravitational field (E) of the earth with distance (r) from the centre of the earth is correctly represented by:

Answer: 1

Question 189. Kepler’s third law states that the square of the period of revolution (T) of a planet around the sun, is proportional to the third power of average distance r between the sun and planet i.e. T² = Kr³ here K is constant. If the masses of the sun and planet are M and m respectively then as per Newton’s law of gravitation force of attraction between them is \(\mathrm{F}=\frac{G M m}{r^2}\) r, here G is gravitational constant. The relation between G and K is described as:

1. GMK = 4π²
2. K = G
3. \(\mathrm{K}=\frac{1}{G}\)
4. GK = 4π²

Answer: 1. GMK = 4π²

Question 190. A remote-sensing satellite of the earth revolves in a circular orbit at a height of 0.25 × 10⁶ m above the surface of the earth. If the earth’s radius is 6.38 × 10⁶ m and g = 9.8 ms^-2, then the orbital speed of the satellite is :

1. 8.56 km s^-1
2. 9.13 km s^-1
3. 6.67 km s^-1
4. 7.76 km s^-1

Answer: 4. 7.76 km s^-1

Question 191. At what height from the surface of the earth are the gravitational potential and the value of g –5.4 × 107 J kg^-2 and 6.0 ms^-2 respectively? Take the radius of the earth as 6400 km.

1. 2000 km
2. 2600 km
3. 1600 km
4. 1400 km

Answer: 2. 2600 km

Question 192. A satellite S is moving in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth. Then,

1. The total mechanical energy of S varies periodically with time.
2. The linear momentum of S remains constant in magnitude.
3. The acceleration of S is always directed towards the centre of the earth.
4. The angular momentum of S about the centre of the earth changes in direction, but its magnitude remains constant.

Answer: 3. The acceleration of S is always directed towards the centre of the earth.

Question 193. The ratio of escape velocity at earth (ve) to the escape velocity at a planet (vp) whose radius and mean density are twice that of earth is:

1. \(1: \sqrt{2}\)
2. 1: 2
3. \(1: 2 \sqrt{2}\)
4. 1: 4

Answer: 3. \(1: 2 \sqrt{2}\)

Question 194. Starting from the centre of the earth having radius r, the variation of g (acceleration due to gravity) is shown by

Answer: 3

Question 195. A satellite of mass m is orbiting the earth (of radius R) at a height h from its surface. The total energy of the satellite in terms of g0, the value of acceleration due to gravity at the earth’s surface, is

1. \(-\frac{2 m g_0 R^2}{R+h}\)
2. \(\frac{\mathrm{mg}_0 \mathrm{R}^2}{2(\mathrm{R}+\mathrm{h})}\)
3. \(-\frac{m g_0 R^2}{2(R+h)}\)
4. \(\frac{\mathrm{Rmg}_0 \mathrm{R}^2}{\mathrm{R}+\mathrm{h}}\)

Answer: 3. \(-\frac{m g_0 R^2}{2(R+h)}\)

Question 196. A physical quantity of the dimensions of length that can be formed out of c, G and \(\frac{e^2}{4 \pi \epsilon_0}\) is the velocity of light, G is a universal constant of gravitation and e is charge] :

1. \(\frac{1}{c^2}\left[G \frac{e^2}{4 \pi \epsilon_0}\right]^{1 / 2}\)
2. \(c^2\left[G \frac{e^2}{4 \pi \epsilon_0}\right]^{1 / 2}\)
3. \(\frac{1}{c^2}\left[\frac{e^2}{G 4 \pi \epsilon_0}\right]^{1 / 2}\)
4. \(\frac{1}{c} G \frac{e^2}{4 \pi \epsilon_0}\)

Answer: 1. \(\frac{1}{c^2}\left[G \frac{e^2}{4 \pi \epsilon_0}\right]^{1 / 2}\)

Question 197. Suppose the charge of a proton and an electron differ slightly. One of them is – e, and the other is (e + Δe). If the net of electrostatic force and the gravitational force between two hydrogen atoms placed at a distance d (much greater than atomic size) apart is zero, then Δe is of the order of [Given the mass of hydrogen mh = 1.67 × 10^-27 kg]

1. 10^-20 C
2. 10^-23 C
3. 10^-37 C
4. 10^-47 C

Answer: 3. 10^-37 C

Question 198. Two astronauts are floating in gravitational-free space after having lost contact with their spaceship. The two will :

1. Keep floating at the same distance between them
2. Move towards each other
3. Move away from each other
4. Will become stationary

Answer: 2. Move towards each other

Question 199. The kinetic energies of a planet in an elliptical orbit about the Sun, at positions A, B and C are KA, KB and KC, respectively. AC is the major axis and SB is perpendicular to AB at the position of the Sun S as shown in the figure. Then

1. K_A < K_B < K_C
2. K_B > K_A > K_C
3. K_B < K_A < K_C
4. K_A > K_B > K_C

Answer: 4. K_A > K_B > K_C

Question 200. If the mass of the Sun were ten times smaller and the universal gravitational constant were ten times larger in magnitude, which of the following is not correct?

1. Raindrops will fall faster.
2. ‘g’ on the Earth will not change
3. Time period of a simple pendulum on the Earth would decrease.
4. Walking on the ground would become more difficult.

Answer: 2. ‘g’ on the Earth will not change

Question 201. The work done to raise a mass m from the surface of the earth to a height h, which is equal to the radius of the earth, is :

1. \(\frac{3}{2} \mathrm{mgR}\)
2. mgR
3. 2 mgR
4. \(\frac{1}{2} \mathrm{mgR}\)

Answer: 4. \(\frac{1}{2} \mathrm{mgR}\)

Question 202. The time period of a geostationary satellite is 24 h, at a height of 6R_E (R_E is the radius of the earth) from the surface of the earth. The time period of another satellite whose height is 2.5 R_E from the surface will be :

1. \(6 \sqrt{2} h\)
2. \(12 \sqrt{2} h\)
3. \(\frac{24}{2.5} h\)
4. \(\frac{12}{2.5} h\)

Answer: 1. \(6 \sqrt{2} h\)

Question 203. Assuming that the gravitational potential energy of an object at infinity is zero, the change in potential energy (final – initial) of an object of mass m, when taken to a height h from the surface of the earth (of radius R), is given by :

1. \(-\frac{\mathrm{GMm}}{\mathrm{R}+\mathrm{h}}\)
2. \(\frac{\mathrm{GMmh}}{\mathrm{R}(\mathrm{R}+\mathrm{h})}\)
3. mgh
4. \(\frac{\mathrm{GMm}}{\mathrm{R}+\mathrm{h}}\)

Answer: 2. \(\frac{\mathrm{GMmh}}{\mathrm{R}(\mathrm{R}+\mathrm{h})}\)

Question 204. A body weight of 72N on the surface of the earth. What is the gravitational force on it at a height equal to half the radius of the earth?

1. 24N
2. 48 N
3. 32 N
4. 30 N

Answer: 3. 32 N

Question 205. The escape velocity from the Earth’s surface is υ. The escape velocity from the surface of another planet having a radius, four times that of Earth and the same mass density is:

1. 2υ
2. 3υ
3. 4υ
4. υ

Answer: 3. 4υ

Question 206. A particle of mass ‘m’ is projected with a velocity u = kV_e (k < 1) from the surface of the earth. (V_e = escape velocity) The maximum height above the surface reached by the particle is

1. \(\mathrm{R}\left(\frac{\mathrm{k}}{1+\mathrm{k}}\right)^2\)
2. \(\frac{\mathrm{R}^2 \mathrm{k}}{1+\mathrm{k}}\)
3. \(\frac{\mathrm{Rk}^2}{1-\mathrm{k}^2}\)
4. \(R\left(\frac{k}{1-k}\right)^2\)

Answer: 3. \(\frac{\mathrm{Rk}^2}{1-\mathrm{k}^2}\)

Question 207. The height at which the acceleration due to gravity becomes \(\) (where g = the acceleration due to gravity on the surface of the earth) in terms of R, the radius of the earth, is

1. \(\frac{R}{\sqrt{2}}\)
2. \(\frac{R}{2}\)
3. \(\sqrt{2} R\)
4. 2R

Answer: 4. 2R

Question 208. Two bodies of masses m and 4 m are placed at a distance r. The gravitational potential at a point on the line joining them where the gravitational field is zero is:

1. Zero
2. \(-\frac{4 G m}{r}\)
3. \(-\frac{6 G m}{r}\)
4. \(-\frac{9 G m}{r}\)

Answer: 4. \(-\frac{9 G m}{r}\)

Question 209. Two particles of equal mass ‘m’ go around a circle of radius R under the action of their mutual gravitational attraction. The speed of each particle with respect to its centre of mass is:

1. \(\sqrt{\frac{G m}{4 R}}\)
2. \(\sqrt{\frac{G m}{3 R}}\)
3. \(\frac{G m M}{2 R}\)
4. \(\frac{G m M}{3 R}\)

Answer: 1. \(\sqrt{\frac{G m}{4 R}}\)

Question 210. What is the minimum energy required to launch a satellite of mass m from the surface of a planet of mass M and radius R in a circular orbit at an altitude of 2R?

1. \(\frac{5 G m M}{6 R}\)
2. \(\frac{2 G m M}{3 R}\)
3. \(\frac{G m M}{2 R}\)
4. \(\frac{G m M}{3 R}\)

Answer: 1. \(\frac{5 G m M}{6 R}\)

Question 211. Four particles, each of mass M and equidistant from each other move along a circle of radius R under the action of their mutual gravitational attraction. the speed of each particle is:

1. \(\sqrt{\frac{G M}{R}}\)
2. \(\sqrt{2 \sqrt{2} \frac{G M}{R}}\)
3. \(\sqrt{\frac{G M}{R}(1+2 \sqrt{2})}\)
4. \(\frac{1}{2} \sqrt{\frac{G M}{R}(1+2 \sqrt{2})}\)

Answer: 4. \(\frac{1}{2} \sqrt{\frac{G M}{R}(1+2 \sqrt{2})}\)

Question 212. From a solid sphere of mass M and radius R, a spherical portion of radius R/2 is removed, as shown in the figure. Taking gravitational potential V = 0 at r = ∞, the potential at the centre of the cavity thus formed is :(G = gravitational constant)

1. \(\frac{-G M}{2 R}\)
2. \(\frac{-G M}{R}\)
3. \(\frac{-2 G M}{3 R}\)
4. \(\frac{-2 G M}{R}\)

Answer: 2. \(\frac{-G M}{R}\)

Question 213. If the angular momentum of a planet of mass m, moving around the sun in a circular orbit is L, about the centre of the Sun, its areal velocity is:

1. \(\frac{2 L}{m}\)
2. \(\frac{4 \mathrm{~L}}{\mathrm{~m}}\)
3. \(\frac{L}{2 m}\)
4. \(\frac{\mathrm{L}}{\mathrm{m}}\)

Answer: 3. \(\frac{L}{2 m}\)

Question 214. The energy required to take a satellite to a height ‘h’ above Earth’s surface (radius or Earth = 6.4 × 10³ km) is E₁ and the kinetic energy required for the satellite to be in a circular orbit at this height is E₂. The value of h for which E₁ and E₂ are equal is :

1. 1.28 × 10⁴ km
2. 6.4 × 10³ km
3. 3.2 × 10³ km
4. 1.6 × 10³ km

Answer: 3. 3.2 × 10³ km

Question 215. A satellite is moving with a constant speed v in a circular orbit around the earth. An object of mass ‘m’ is ejected from the satellite such that it just escapes from the gravitational pull of the earth. At the time of ejection, the kinetic energy of the object is :

1. \(\frac{3}{2} m v^2\)
2. \(\frac{1}{2} m v^2\)
3. 2mv²
4. mv²

Answer: 4. mv²

Question 216. Two stars of masses 3 × 10³¹ kg each, and at distance 2 × 10¹¹ m rotate in a plane about their common centre of mass O. A meteorite passes through O moving perpendicular to the star’s rotation plane. In order to escape from the gravitational field of this double star, the minimum speed that a meteorite should have at O is (Take Gravitational constant G = 6.67 × 10^-11 Nm2 kg^-2) What is the order of energy of the gas due to its thermal motion?

1. 3.8 × 10⁴ m/s
2. 1.4 × 10⁵ m/s
3. 2.8 × 10⁵ m/s
4. 2.4 × 10⁴ m/s

Answer: 3. 2.8 × 10⁵ m/s

Question 217. A satellite is revolving in a circular orbit at a height h from the earth’s surface, such that h<<R where R is the radius of the earth. Assuming that the effect of the earth’s atmosphere can be neglected. The minimum increase in the speed required so that the satellite could escape from the gravitational field of the earth is :

1. \(\sqrt{g R}(\sqrt{2}-1)\)
2. \(\sqrt{\frac{g R}{2}}\)
3. \(\sqrt{2 \mathrm{gR}}\)
4. \(\sqrt{g R}\)

Answer: 1. \(\sqrt{g R}(\sqrt{2}-1)\)

Chapter 7 Gravitation NEET MCQs and Answer Explanations

Question 218. The mass and the diameter of a planet are three times the respective values for the Earth. The period of oscillation of a simple pendulum on the Earth is 2 s. The period of oscillation of the same pendulum on the planet would be: 

1. \(\frac{3}{2} s\)
2. \(\frac{2}{\sqrt{3}} \mathrm{~s}\)
3. \(\frac{\sqrt{3}}{2} s\)
4. \(2 \sqrt{3} \mathrm{~s}\)

Answer: 4. \(2 \sqrt{3} \mathrm{~s}\)

Question 219. A straight rod of length L extends from x = a to x = L + a. The gravitational force it exerts on a point mass ‘m’ at x = 0, if the mass per unit length of the rod is A + Bx², is given by

1. \(G m\left[A\left(\frac{1}{a+L}-\frac{1}{a}\right)-B L\right]\)
2. \({Gm}\left[A\left(\frac{1}{a+L}-\frac{1}{a}\right)+B L\right]\)
3. \({Gm}\left[A\left(\frac{1}{a}-\frac{1}{a+L}\right)+B L\right]\)
4. \(G m\left[A\left(\frac{1}{a}-\frac{1}{a+L}\right)-B L\right]\)

Answer: 3. \({Gm}\left[A\left(\frac{1}{a}-\frac{1}{a+L}\right)+B L\right]\)

NEET Class 11 Physics Gravitation Multiple Choice Questions and Solutions

Question 220. A satellite of mass M is in a circular orbit of radius R about the centre of the earth. A meteorite of the same mass, falling towards the earth, collides with the satellite completely inelastically. The speeds of the satellite and the meteorite are the same, just before the collision. the subsequent motion of the combined body will be :

1. In the same circular orbit of radius R
2. Such that it escapes to infinity
3. In an elliptical orbit
4. In a circular orbit of a different radius

Answer: 3. In an elliptical orbit

Question 221. Two satellites, A and B, have masses of m and 2m respectively. A is in a circular orbit of radius R, and B is in a circular orbit of radius 2R around the earth. The ratio of their kinetic energies, \(\frac{T_{\mathrm{A}}}{\mathrm{T}_{\mathrm{B}}}\) is:

1. 1
2. \(\sqrt{\frac{1}{2}}\)
3. 2
4. \(\frac{1}{2}\)

Answer: 1. 1

Friction Multiple Choice Question And Answers

Question 1. If the normal force is doubled, the coefficient of friction is:

1. Halved
2. Doubled
3. Tripled
4. Not changed

Answer: 4. Halved

Question 2. If the coefficient of friction of a plane inclined at 45º is 0.5, then the acceleration of a body sliding freely on it is (g = 9.8m/s²)-

1. 4.9 m/s²
2. 9.8 m/s²
3. \(\frac{9.8}{\sqrt{2}} \mathrm{~m} / \mathrm{s}^2\)
4. \(\frac{9.8}{2 \sqrt{2}} \mathrm{~m} / \mathrm{s}^2 \)

Answer: 4. \(\frac{9.8}{2 \sqrt{2}} \mathrm{~m} / \mathrm{s}^2 \)

Question 3. A body of mass 100 g is sliding downward from an inclined plane of inclination 30°. What is the frictional force experienced if µ = 1.7 –

1. \(1.7 \times \sqrt{2} \times \frac{1}{\sqrt{3}} \mathrm{~N}\)
2. \(1.7 \times \sqrt{3} \times \frac{1}{2} \mathrm{~N}\)
3. \(1.7 \times \sqrt{3} \mathrm{~N}\)
4. \(1.7 \times \sqrt{2} \times \frac{1}{3} \mathrm{~N}\)

Answer: 2. \(1.7 \times \sqrt{3} \times \frac{1}{2} \mathrm{~N}\)

Friction MCQs for NEET Physics Class 11 with Answers

Question 4. A car is moving along a straight horizontal road with a speed v₀. If the coefficient of friction between the tyres and the road is µ then the shortest distance in which the car can be stopped is-

1. \(\frac{v_0^2}{2 \mu \mathrm{g}}\)
2. \(\frac{v_0}{\mu g}\)
3. \(\left(\frac{v_0}{\mu g}\right)^2\)
4. \(\frac{1}{\sqrt{3}}\)

Answer: 1. \(\frac{v_0^2}{2 \mu \mathrm{g}}\)

Question 5. A block of mass 10 kg is moving up an inclined plane of inclination 30° with an initial speed of 5 m/s. It stops after 0.5 s, what is the value of the coefficient of kinetic friction?

1. 0.5
2. 0.6 cm
3. \(\sqrt{3}\)
4. \(\frac{1}{\sqrt{3}}\)

Answer: 4. \(\frac{1}{\sqrt{3}}\)

Question 6. A particle is projected along a rough plane inclined at an angle of 45° with the horizontal if the \(\frac{1}{2}\) coefficient of friction is g

1. \(\frac{\mathrm{g}}{\sqrt{2}}\)
2. \(\frac{\mathrm{g}}{2}\)
3. \(\frac{g}{\sqrt{2}}\left(1+\frac{1}{2}\right)\)
4. \(\frac{g}{\sqrt{2}}\left(1-\frac{1}{2}\right)\)
5. Answer: 3. \(\frac{g}{\sqrt{2}}\left(1+\frac{1}{2}\right)\)

Question 7. A body of mass 10 kg lies on a rough horizontal surface. When a horizontal force of F newtons acts on it, it gets an acceleration of 5 m/s². And when the horizontal force is doubled, it gets an acceleration of 18 m/s². The coefficient of friction between the body and the horizontal surface is- (Take g = 10 m/s²)

1. 0.2
2. 0.4
3. 0.6
4. 0.8

Answer: 4. 0.8

Question 8. On the horizontal surface of a truck, a block of mass 1kg is placed (μ = 0.6) and the truck is moving with acceleration 5 m/sec², then frictional force on the block will be –

1. 5 N
2. 6 N
3. 5.88 N
4. 8 N

Answer: 1. 5 N

Question 9. A 10 kg box is placed on a surface. The coefficient of friction between the surface and box is μ = 0.5. If horizontal force 100 N is applied acceleration of the box will be (g = 10 m/sec²) –

1. 2.5 m/s²
2. 5 m/s²
3. 7.5 m/s²
4. None

Answer: 2. 5 m/s²

Question 10. A block B is pushed momentarily along a horizontal surface with an initial velocity v. If μ is the coefficient of sliding friction between B and the surface, block B will come to rest after a time:

1. \(\frac{v}{g \mu}\)
2. \(\frac{g \mu}{v}\)
3. \(\frac{g}{v}\)
4. \(\frac{v}{g}\)

Answer: 1. \(\frac{v}{g \mu}\)

Question 11. A block of mass 5 kg is placed on a horizontal surface and a pushing force of 20 N is acting on the back as shown in the figure. If the coefficient of friction between the block and surface is 0.2, then calculate the frictional force and speed of the block after 15 seconds. (Given g = 10 m/s²)

1. 2.936 MS^-1
2. 4.936 MS^-1
3. 3.936 MS^-1
4. None of these

Answer: 3. 3.936 MS^-1

Question 12. A marble block of mass 2 kg lying on ice when given a velocity of 6 m/s is stopped by friction in 10s. Then the coefficient of friction is :

1. 0.02
2. 0.03
3. 0.06
4. 0.01

Answer: 3. 0.06

NEET Physics Chapter 6 Friction MCQs and Answer Key

Question 13. Consider a car moving on a straight road with a speed of 100 m/s. The distance at which the car can be stopped is (µ_k= 0.5)

1. 100 m
2. 400 m
3. 800 m
4. 1000 m

Answer: 4. 1000 m

Question 14. Starting from rest a body slides down a 45º inclined plane in twice the time it takes to slide down the same distance in the absence of friction. The coefficient of friction between the body and the inclined plane is:

1. 0.75
2. 0.33
3. 0.25
4. 0.80

Answer: 1. 0.75

Question 15. A wooden block of mass m resting on a rough horizontal table (coefficient of friction = μ) is pulled by a force F as shown in the figure. The acceleration of the block moving horizontally is :

1. \(\frac{F \cos \theta}{m}\)
2. \(\frac{\mu F \sin \theta}{M}\)
3. \(\frac{F}{m}(\cos \theta+\mu \sin \theta)-\mu g\)
4. None

Answer: 3. \(\frac{F}{m}(\cos \theta+\mu \sin \theta)-\mu g\)

Question 16. A block of mass M = 5 kg is resting on a rough horizontal surface for which the coefficient of friction is 0.2. When a force F = 40 N is applied, the acceleration of the block will be (g = 10 m/s²) :

1. 5.73 m/sec²
2. 8.0 m/sec²
3. 3.17 m/sec²
4. 10.0 m/sec²

Answer: 1. 5.73 m/sec²

Question 17. A body is projected up a rough inclined plane from the bottom with some velocity. It travels up the incline and then returns back. If the time of ascent is and time of descent is td, then

1. t_a= t_d
2. t_a> t_d
3. t_a< t_d
4. Data insufficient

Answer: 3. t_a< t_d

Question 18. The upper half of an inclined plane with inclination φ is perfectly smooth while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom of the coefficient of friction for the lower half is given by

1. 2 tan φ
2. tan φ
3. 2 sin φ
4. 2 cos φ

Answer: 1. 2 tan φ

Question 19. The frictional force is –

1. Self-adjustable
2. Not self-adjustable
3. scalar quantity
4. Equal to the limiting force

Answer: 1. Self-adjustable

Question 20. A block is placed on a rough floor and a horizontal force F is applied to it. The force of friction f by the floor on the block is measured for different values of F and a graph is plotted between them-

1. The graph is a straight line of slope 45°
2. The graph is a straight line parallel to the F-axis
3. The graph is a straight line of slope 45° for small F and a straight line parallel to the F-axis for large F.
4. There is a small kink on the graph

1. 3, 4
2. 1, 4
3. 1, 2
4. 1, 3

Answer: 1. 3, 4

Question 21. A block A kept on an inclined surface just begins to slide if the inclination is 30°. The block is replaced by another block B and it is found that it just begins to slide if the inclination is 40° –

1. Mass of A > mass of B
2. Mass of A < mass of B
3. Mass of A = mass of B
4. All three are possible

Answer: 4. All the three are possible

Question 22. It is easier to pull a body than to push, because-

1. The coefficient of friction is more in pushing than in pulling
2. The friction force is more in pushing than in pulling
3. The body does not move forward when pushed.
4. None of these

Answer: 2. The friction force is more in pushing than that in pulling

Question 23. The coefficient of static friction between two surfaces depends on –

1. Nature of surfaces
2. The shape of the surfaces in contact
3. The area of contact
4. All of the above

Answer: 1. Nature of surfaces

Question 24. A box is lying on an inclined plane. If the box starts sliding when the angle of inclination is 60°, then the coefficient of static friction of the box and plane is-

1. 2.732
2. 1.732
3. 0.267
4. 0.176

Answer: 2. 1.732

Question 25. A 20 kg block is initially at rest. A 75 N force is required to set the block in motion. After the motion, a force of 60 N is applied to keep the block moving at a constant speed. The coefficient of static friction is-

1. 0.6
2. 0.52
3. 0.44
4. 0.35

Answer: 4. 0.35

Question 26. A block of metal is lying on the floor of a bus. The maximum acceleration which can be given to the bus so that the block may remain at rest will be

1. µg
2. \(\frac{\mu}{g}\)
3. µ²g
4. µg²

Answer: 1. µg

Question 27. A box ‘A’ is lying on the horizontal floor of the compartment of a train running along horizontal rails from left to right. At time ‘t’, it decelerates. Then the reaction R by the floor on the box is given best by :

Answer: 3

Question 28. A block of mass 0.1 kg is held against a wall by applying a horizontal force of 5N on the block. If the coefficient of friction between the block and the wall is 0.5, the magnitude of frictional force acting on the block is (g = 9.8m/s²)

1. 2.5 N
2. 0.98 N
3. 4.9 N
4. 0.49 N

Answer: 2. 0.98 N

Question 29. A block of mass 2 kg rests on a rough inclined plane making an angle of 300 with the horizontal. The coefficient of static friction between the block and the plane is 0.7. The frictional force on the block is (g = 9.8m/s²) :

1. 9.8 N
2. 0.7 × 9.8 N
3. 9.8 × 7 N
4. 0.8 × 9.8 N

Answer: 1. 9.8 N

NEET Class 11 Friction Multiple Choice Questions

Question 30. A block of mass 5 kg and surface area 2 m² just begins to slide down on an inclined plane when the angle of inclination is 30º. Keeping the mass the same, the surface area of the block is doubled. The angle at which it starts sliding down is :

1. 30º
2. 60º
3. 15º
4. None

Answer: 1. 30º

Question 31. A 60 kg body is pushed horizontally with just enough force to start it moving across a floor and the same force continues to act afterwards. The coefficient of static friction and sliding friction are 0.5 and 0.4 respectively. The acceleration of the body is (g = 10m/s²) :

1. 6 m/s²
2. 4.9 m/s²
3. 3.92 m/s²
4. 1 m/s²

Answer: 4. 1 m/s²

Question 32. The blocks A and B are arranged as shown in the figure. The pulley is frictionless. The mass of A is 10 kg. The coefficient of friction between block A and the horizontal surface is 0.20. The minimum mass of B to start the motion will be

1. 2 kg
2. 0.2 kg
3. 5 kg
4. 10 kg

Answer: 1. 2 kg

Question 33. In the case of a horse pulling a cart, the force that causes the horse to move forward is the force that :

1. The horse exerts on the ground
2. The horse exerts on the cart
3. The ground exerts on the horse
4. The cart exerts on the horse

Answer: 3. The ground exerts on the horse

Question 34. A uniform rope of length l lies on a table. If the coefficient of friction is μ then the maximum length I₁ of the part of this rope which can overhang from the edge of the table without sliding down is

1. \(\frac{\ell}{\mu}\)
2. \(\frac{\ell}{\mu+1}\)
3. \(\frac{\mu \ell}{1+\mu}\)
4. \(\frac{\mu \ell}{1-\mu}\)

Answer: 3. \(\frac{\mu \ell}{1+\mu}\)

Question 35. Block A of mass 4 kg and block B of mass 6 kg are resting on a horizontal surface as shown in the figure. There is no friction between the block B and the horizontal surface. The coefficient of friction between the blocks is 0.2. If the value of g = 10 ms^-2, the maximum horizontal force F that can be applied on block B without any relative motion between A and B is

1. 20 N
2. 40 N
3. 60 N
4. 100 N

Answer: 1. 20 N

Question 36. Consider the situation. The wall is smooth but the surfaces of A and B in contact are rough. The friction on B due to A in equilibrium-

1. Is upward
2. Is downward
3. Is zero
4. The system cannot remain in equilibrium

Answer: 4. The system cannot remain in equilibrium

Question 37. Suppose all the surfaces in the previous problem are rough. The direction of friction on B due to A-

1. Is upward
2. Is downward
3. Is zero
4. Depends on the masses of A and B

Answer: 1. Is upward

NEET Physics Class 11 Chapter 6 Friction Multiple Choice Questions and Answers

Question 38. A body of mass M is kept on a rough horizontal surface (friction coefficient = µ). A person is trying to pull the body by applying a horizontal force but the body is not moving. The force by the surface on A is F where-

1. F = Mg
2. F = µMg
3. \(M g \leq F \leq M g \sqrt{1+\mu^2}\)
4. \(M g \geq F \geq M g \sqrt{1+\mu^2}\)

Answer: 3. \(M g \leq F \leq M g \sqrt{1+\mu^2}\)

Question 39. In a situation where the contact force by a rough horizontal surface on a body placed on it has constant magnitude if the angle between this force and the vertical is decreased the frictional force between the surface and the body will-

1. Increase
2. Decrease
3. Remain the same
4. May increase or decrease

Answer: 2. Decrease

Question 40. An inclined plane is inclined at an angle θ with the horizontal. A body of mass m rests on it, if the coefficient of friction is µ, then the minimum force that has to be applied to the inclined plane to make the body just move up the inclined plane is-

1. mgsinθ
2. µmgcosθ
3. µmgcosθ – mgsinθ
4. µmgcosθ + mgsinθ

Answer: 4. µmgcosθ + mgsinθ

Question 41. A block W is held against a vertical wall by applying a horizontal force F. The minimum value of F needed to hold the block is if μ < 1

1. Less than W
2. Equal to W
3. Greater than W
4. Data is insufficient

Answer: 3. Greater than W

Question 42. The system shown in the figure is in equilibrium. The maximum value of W, so that the maximum value of static frictional force on 100 kg body is 450 N, will be:-

1. 100 N
2. 250 N
3. 450 N
4. 1000 N

Answer: 3. 450 N

Friction NEET Class 11 MCQs with Detailed Solutions

Question 43. A block of mass 20 kg is kept on a rough incline plane. If the angle of repose is 30°, then what should be the value of F_ext so that the block does not move over the inclined plane?

1. 120 N
2. 200 N
3. 110 N
4. Both 1 and 2

Answer: 4. Both 1 and 2

Question 44. What is the maximum value of the force F such that the block shown in the arrangement, does not move :

1. 20 N
2. 10 N
3. 12 N
4. 15 N

Answer: 1. 20 N

Question 45. The coefficient of static friction, μs, between block A of mass 2kg and the table as shown in the figure, is 0.2. What would be the maximum mass value of block B so that the two blocks do not move? The string and the pulley are assumed to be smooth and massless : (g = 10 m/s²)

1. 2.0 kg
2. 4.0 kg
3. 0.2 kg
4. 0.4 kg

Answer: 4. 0.4 kg

Question 46. A horizontal force of 10 N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is 0.2. The weight of the block is :

1. 2 kg
2. 50 N
3. 100 N
4. 2 N

Answer: 4. 2 N

Question 47. A block rests on a rough inclined plane making an angle of 30º with the horizontal. The coefficient of static friction between the block and the plane is 0.8. If the frictional force on the block is 10 N, the mass of the block (in kg) is (take g = 10 m/s²) :

1. 2.0
2. 4.0
3. 1.6
4. 2.5

Answer: 1. 2.0

Question 48. A block of mass 20 kg is acted upon by a force F = 30 N at an angle of 53° with the horizontal in a downward direction as shown. The coefficient of friction between the block and the horizontal surface is 0.2. The friction force acting on the block by the ground is (g = 10 m/s²)

1. 40.0 N
2. 30.0 N
3. 18.0 N
4. 44.8 N

Answer: 3. 18.0 N

Question 49. A block of mass m lying on a rough horizontal plane is acted upon by a horizontal force P and another force Q inclined at an angle θ to the vertical. The block will remain in equilibrium if the coefficient of friction between it and the surface is:-

1. \(\frac{P+Q \sin \theta}{m g+Q \cos \theta}\)
2. \(\frac{P \cos \theta+Q}{m g-Q \sin \theta}\)
3. \(\frac{P+Q \cos \theta}{m g+Q \sin \theta}\)
4. \(\frac{P \sin \theta+Q}{m g-Q \cos \theta}\)

Answer: 1. \(\frac{P+Q \sin \theta}{m g+Q \cos \theta}\)

Question 50. In the arrangement shown in the figure, a 5 kg block is placed on a rough table (μ =0.4) and a 3kg mass is connected at one end. then the range of mass m, for which the system will remain in equilibrium is

1. 1 kg to 3 kg
2. 1 kg to 5 kg
3. Any value greater than 8 kg
4. 3 kg to 5 kg

Answer: 2. 1 kg to 5 kg

Question 51. Two masses A and B of 10 kg and 5 kg respectively are connected with a string passing over a frictionless pulley fixed at the corner of a table as shown. The coefficient of static friction of A with table is 0.2. The minimum mass of C that may be placed on A to prevent it from moving is

1. 15 kg
2. 10 kg
3. 5 kg
4. 12 kg

Answer: 1. 15 kg

Question 52. A block of mass m is at rest relative to the stationary wedge of mass M. The coefficient of friction between block and wedge is µ. The wedge is now pulled horizontally with acceleration ‘a’ as shown in the figure. Then the minimum magnitude of ‘a’ for the friction between block and wedge to be zero is :

1. g tan θ
2. µ g tan θ
3. g cot θ
4. µ g cot θ

Answer: 3. g cot θ

Question 53. A uniform rope of length l lies on a table. If the coefficient of friction is
μ, then the maximum length l₁ of the part of this rope which can overhang from the edge of the table without sliding down is

1. \(\frac{l}{\mu}\)
2. \(\frac{l}{\mu+l}\)
3. \(\frac{\mu l}{1+\mu}\)
4. \(\frac{\mu l}{\mu-1}\)

Answer: 3. \(\frac{\mu l}{1+\mu}\)

Question 54. A heavy uniform chain lies on a horizontal tabletop. If the coefficient of friction between the chain and table surface is 0.25, then the maximum fraction of the length of the chain, that can hang over one edge of the table is

1. 20%
2. 25%
3. 35%
4. 15%

Answer: 1. 20%

Question 55. A uniform chain of length L changes partly from a table which is kept in equilibrium by friction. The maximum length that can withstand without slipping is l, and then the coefficient of friction between the table and the chain is

1. \(\frac{l}{L}\)
2. \(\frac{l}{L+l}\)
3. \(\frac{l}{L-1}\)
4. \(\frac{L}{L+l}\)

Answer: 3. \(\frac{l}{L-1}\)

Question 56. A uniform metal chain is placed on a rough table such that one end of the chain hangs down over the edge of the table. When one-third of its length hangs over the edge, the chain starts sliding. Then, the coefficient of static friction is

1. \(\frac{3}{4}\)
2. \(\frac{1}{4}\)
3. \(\frac{2}{3}\)
4. \(\frac{1}{2}\)

Answer: 4. \(\frac{1}{2}\)

Question 57. A rope lies on a table such that part of it lays over. The rope begins to slide when the length of the hanging part is 25 % of the entire length. The coefficient of friction between the rope and the table is:

1. 0.33
2. 0.25
3. 0.5
4. 0.2

Answer: 1. 0.33

Question 58. Two blocks A and B placed on a plane surface as shown in the figure. The mass of block A is 100 kg and that of block B is 200 kg. Block A is tied to a stand and block B is pulled by a force F. If the coefficient of friction between the surfaces of A and B is 0.2 and the coefficient of friction between B and the plane is 0.3 then for the motion of B the minimum value of F will be

1. 700 N
2. 1050 N
3. 900 N
4. 1100 N

Answer: 4. 1100N

NEET Physics Gravitation Chapter 6 Friction MCQs and Answers

Question 59. A 40 kg slab rests on a frictionless floor. A 10 kg block rests on top of the slab. The static coefficient of friction between the block and slab is 0.60 while the kinetic coefficient is 0.40. The 10 kg block is acted upon by a horizontal force of 100N. If g = 9.8 m/s², the resulting acceleration of the slab will be

1. 0.98 m/s²
2. 1.47 m/s²
3. 1.52 m/s²
4. 6.1 m/s²

Answer: 1. 0.98 m/s²

Question 60. A body A of mass 1kg rests on a smooth surface. Another body B of mass 0.2 kg is placed over A as shown. The coefficient of static friction between A and B is 0.15. B will bring to slide on A if a pulled with a force greater than-

1. 1.764 N
2. 0.1764 N
3. 0.3 N
4. It will not slide for any F

Answer: 1. 1.764 N

Question 61. A ramp is constructed with a parabolic shape such that the height y at any point on its surface is given in terms of its horizontal distance x from the bottom of the ramp (x = y = 0) by y =. A small block is to be set on the ramp. The maximum height from the bottom level at which the block can be kept on the ramp without sliding is (Given that μ_s= 0.5)

1. 2.5 m
2. 5 m
3. 1.25 m
4. 2.75 m

Answer: 3. 1.25 m

Question 62. Two blocks A and B of equal masses are sliding down along straight parallel lines on an inclined plane of 45°. Their coefficients of kinetic friction are μ_A= 0.2 and μ_B= 0.3 respectively. At t = 0, both the blocks are at rest and block A is \(\sqrt{2}\) 2 meters behind block B. The time and distance from the initial position where the front faces of the blocks come in line on the inclined plane as shown in the figure. (Use g = 10 ms^-2.)

1. \(2 \mathrm{~s}, 8 \sqrt{2} \mathrm{~m}\)
2. \(\sqrt{2} \mathrm{~s}, 7 \mathrm{~m}\)
3. \(\sqrt{2} \mathrm{~s}, 7 \sqrt{2} \mathrm{~m}\)
4. \(2 \mathrm{~s}, 7 / \sqrt{2} \mathrm{~m}\)

Answer: 1. \(2 \mathrm{~s}, 8 \sqrt{2} \mathrm{~m}\)

Question 63. A block of mass m is on an inclined plane of angle θ. The coefficient of friction between the block and the plane is μ and tanθ > μ. The block is held stationary by applying a force P parallel to the plane. The direction of force pointing up the plane is taken to be positive. As P is varied from P₁= mg(sinθ – μcosθ) to P₂= mg(sinθ + μcosθ), the frictional force f versus P graph will look like :

Answer: 1

Question 64. A smooth block is released at rest on a 45º incline and then slides a distance d. The time taken to slide is n times as much to slide on a rough incline than on a smooth incline. The coefficient of friction is-

1. \(\mu_s=1-\frac{1}{n^2}\)
2. \(\mu_s=\sqrt{1-\frac{1}{n^2}}\)
3. \(\mu_k=1-\frac{1}{n^2}\)
4. \(\mu_k=\sqrt{1-\frac{1}{n^2}}\)

Answer: 3. \(\mu_k=1-\frac{1}{n^2}\)

NEET Class 11 Friction MCQ Practice Test with Answers

Question 65. Two blocks m₁= 4kg and m₂= 2kg, are connected by a weightless rod on a plane having an inclination of 370. The coefficients of dynamic friction of m₁ and m₂ with the inclined plane are μ = 0.25. Then the common acceleration of the two blocks and the tension in the rod are:

1. 4 m/s², T = 0
2. 2 m/s², T = 5 N
3. 10 m/s²,T = 10 N
4. 15 m/s², T = 9N

Answer: 1. 4 m/s2, T = 0

Question 66. A force F = t is applied to block A as shown in the figure. The force is applied at t = 0 seconds when the system is at rest and the string is just straight without tension. Which of the following graphs gives the friction force between B and the horizontal surface as a function of time ‘t’?

Answer: 1

Question 67. If the coefficient of friction between A and B is μ, the maximum horizontal acceleration of the wedge A for which B will remain at rest w.r.t the wedge is :

1. μ g
2. \(g\left(\frac{1+\mu}{1-\mu}\right)\)
3. \(\frac{\mathrm{g}}{\mu}\)
4. \(g\left(\frac{1-\mu}{1+\mu}\right)\)

Answer: 2. \(g\left(\frac{1+\mu}{1-\mu}\right)\)

Question 68. What is the minimum stopping distance for a vehicle of mass m moving with speed v along a level road? If the coefficient of friction between the tyres and the road is μ.

1. \(\frac{v^2}{2 \mu \mathrm{g}}\)
2. \(\frac{2 v^2}{\mu \mathrm{g}}\)
3. \(\frac{v^2}{\mu g}\)
4. None of these

Answer: 1. \(\frac{v^2}{2 \mu \mathrm{g}}\)

Question 69. A block of mass m₁= 1 kg and another mass m₂= 2 kg, are placed together (see figure) on an inclined plane with angle of inclination θ. Various values of θ are given in List 1. The coefficient of friction between the block m₁ and the plane is always zero. The coefficient of static and dynamic friction between the block m₂ and the plane is equal to μ = 0.3. In List 2 expression for the friction on block m₂ is given. Match the correct expression of the friction in List II with the angles given in List 1, and choose the correct option. The acceleration due to gravity is denoted by g.

[Useful information : tan(5.5°) ≈ 0.1 ; tan (11.5°) ≈ 0.2 ; tan(16.5º ≈ 0.3)]

List-1

P. θ = 5°

Q. θ = 10°

R. θ = 15°

S. θ = 20°

List-2

1. m₂g sin θ

2. (m₁+ m₂)g sin θ

3. μm₂g cos θ

4. μ(m₁+ m₂)g cos θ

Code:

1. P-1, Q-1, R-1,S-3
2. P-2, Q-2, R-2,S-3
3. P-2, Q-2, R-2,S-4
4. P-2, Q-2, R-3,S-3

Answer: 4. P-2, Q-2, R-3,S-3

Question 70. A block of mass m is in contact with cart C as shown in the figure.

Friction in NEET Physics Class 11 MCQs and Explanations

The coefficient of static friction between the block and the cart is μ. The acceleration α of the cart that will prevent the block from falling satisfies

1. \(\alpha>\frac{m g}{\mu}\)
2. \(\alpha>\frac{g}{\mu m}\)
3. \(\alpha \geq \frac{g}{\mu}\)
4. \(\alpha<\frac{g}{\mu}\)

Answer: 3. \(\alpha \geq \frac{g}{\mu}\)

Question 71. A conveyor belt is moving at a constant speed of 2m/s. A box is gently dropped on it. The coefficient of friction between them is µ= 0.5. The distance that the box will move relative to the belt before coming to rest on it taking g = 10 ms^-2, is :

1. 1.2 m
2. 0.6 m
3. Zero
4. 0.4 m

Answer: 4. 0.4 m

Question 72. A gramophone record is revolving with an angular velocity ω. A coin is placed at a distance r from the centre of the record. The static coefficient of friction is μ. The coin will revolve with the record if

1. \(\mathrm{r}=\mu \mathrm{g} \omega^2\)
2. \(r=\frac{\omega^2}{\mu g}\)
3. \(r \leq \frac{\mu g}{\omega^2}\)
4. \(r \geq \frac{\mu g}{\omega^2}\)

Answer: 3. \(r \leq \frac{\mu g}{\omega^2}\)

Question 73. A car of mass m is moving on a level circular track of radius R. If μ_s represents the static friction between the road and tyres of the car, the maximum speed of the car in circular motion is given by :

1. \(\sqrt{\mu_s m R g}\)
2. \(\sqrt{R g / \mu_s}\)
3. \(\sqrt{m R g / \mu_s}\)
4. \(\sqrt{\mu_s R g}\)

Answer: 4. \(\sqrt{\mu_s R g}\)

Question 74. A system consists of three masses m₁, m₂ and m₃ connected by a string passing over a pulley P. The mass m₃ hangs freely and m₂ and m₁ are on a rough horizontal table (the coefficient of friction = μ). The pulley is frictionless and of negligible mass. The downward acceleration of mass m₁ is : (Assume m₁= m₂= m₃= m)

1. \(\frac{g(1-g \mu)}{9}\)
2. \(\frac{2 g \mu}{3}\)
3. \(\frac{g(1-2 \mu)}{3}\)
4. \(\frac{g(1-2 \mu)}{2}\)

Answer: 3. \(\frac{g(1-2 \mu)}{3}\)

Question 75. A Block A of mass m₁ rests on a horizontal table. A light string connected to it passes over a frictionless pulley at the edge of a table and from its other end, another block B of mass m₂ is suspended. The coefficient of kinetic friction between the block and the table is μ_k. When the block A is sliding on the table, the tension in the string is :

1. \(\frac{g(1-g \mu)}{9}\)
2. \(\frac{2 g \mu}{3}\)
3. \(\frac{g(1-2 \mu)}{3}\)
4. \(\frac{g(1-2 \mu)}{2}\)

Answer: 2. \(\frac{2 g \mu}{3}\)

Question 76. A plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches 30º the box starts to slip and slides 4.0 m down the plank in 4.0s. The coefficients of static and kinetic friction between the box and the plank will be, respectively :

1. 0.6 and 0.5
2. 0.5 and 0.6
3. 0.4 and 0.3
4. 0.6 and 0.6

Answer: 1. 0.6 and 0.5

Question 77. Which one of the following statements is incorrect?

1. Rolling friction is smaller than sliding friction.
2. The coefficient of sliding friction has dimensions of length.
3. Frictional force opposes the relative motion.
4. The limiting value of static friction is directly proportional to normal reaction.

Answer: 2. Coefficient of sliding friction has dimensions of length.

Question 78. The minimum force required to start pushing a body up a rough (frictional coefficient μ) inclined plane is F₁ while the minimum force needed to prevent it from sliding down is F₂. If the inclined plane makes an F angle θ from the horizontal such that tan θ = 2μ then the ratio \(\frac{F_1}{F_2}\) is :

1. 1
2. 2
3. 3
4. 4

Answer: 3. 3

NEET Physics Chapter 6 Friction: MCQs for Exam Preparation

Question 79. A block of mass m is placed on a surface with a vertical cross-section given by
y =\(\frac{x^3}{6}\). If the coefficient of friction is 0.5, the maximum height above the ground at which the block can be placed without slipping is:

1. \(\frac{1}{6} m\)
2. \(\frac{2}{3} m\)
3. \(\frac{1}{3} m\)
4. \(\frac{1}{2} m\)

Answer: 1. \(\frac{1}{6} m\)

Question 80. Given in the figure are two blocks A and B of weight 20 N and 100 N, respectively. These are being pressed against a wall by a force F as shown. If the coefficient of friction between the blocks is 0.1 and between block B and the wall is 0.15, the frictional force applied by the wall on block B is:

1. 100N
2. 80N
3. 120N
4. 150N

Answer: 3. 120N

Question 81. Two masses m₁ = 5kg and m₂ = 10kg connected by an inextensible string over a frictionless pulley are moving as shown in the figure. The coefficient of friction of the horizontal surface is 0.15. The minimum weight m that should be put on top of m₂ to stop the motion is :

1. 43.3 kg
2. 10.3 kg
3. 18.3 kg
4. 27.3 kg

Answer: 4. 27.3 kg

Question 82. A block of mass 10 kg is kept on a rough inclined plane as shown in the figure. A force of 3N is applied to the block. The coefficient of static friction between the plane and the block is 0.6. What should be the minimum value of force P, such that the block does not move downward (take g = 10 m/s²)

1. 32 N
2. 23 N
3. 25 N
4. 18 N

Answer: 1. 32 N

NEET Class 11 Friction Multiple Choice Questions and Solutions

Question 83. A block kept on a rough inclined plane, as shown in the figure, remains at rest upto a maximum force of 2N down the inclined plane. The maximum external force up the inclined plane that does not move the block is 10 N. The coefficient of static friction between the block and the plane is : (Take g = 10 m/s²)

1. \(\frac{\sqrt{3}}{4}\)
2. \(\frac{1}{2}\)
3. \(\frac{\sqrt{3}}{2}\)
4. \(\frac{2}{3}\)

Answer: 3. \(\frac{\sqrt{3}}{2}\)

Fluid Mechanics Multiple Choice Questions And Answers

Question 1. The height of a mercury barometer is 75 cm at sea level and 50 cm at the top of a hill. The ratio of the density of mercury to that of air is 104. The height of the hill is

1. 250 m
2. 2.5 km
3. 1.25 km
4. 750 m

Answer: 2. 2.5 km

Question 2. If pressure at half the depth of a lake is equal to 2/3 of pressure at the bottom of the lake then what is the depth of the lake

1. 10m
2. 20m
3. 60m
4. 30m

Answer: 2. 20m

Question 3. A uniform tapering vessel is filled with a liquid of density 900 kg/m³. The force that acts on the base of the vessel due to the liquid is (g = 10 ms^-2 )

1. 3.6 N
2. 7.2 N
3. 9.0 N
4. 14.4 N

Answer: 2. 7.2 N

Fluid Mechanics MCQs for NEET Physics Class 11 with Answers

Question 4. The pressure at the bottom of a tank containing a liquid does not depend on

1. Acceleration due to gravity
2. Height of the liquid column
3. Area of the bottom surface
4. Nature of the liquid

Answer: 3. Area of the bottom surface

Question 5. When a large bubble rises from the bottom of a lake to the surface. Its radius doubles. If atmospheric pressure is equal to that of a column of water height H, then the depth of the lake is

1. H
2. 2H
3. 7H
4. 8H

Answer: 3. 7H

Question 6. The volume of an air bubble becomes three times as it rises from the bottom of a lake to its surface. Assuming atmospheric pressure to be 75 cm of Hg and the density of water to be 1/10 of the density of mercury, the depth of the lake is

1. 5m
2. 10m
3. 15m
4. 20m

Answer: 3. 15m

Question 7. The value of g at a place decreases by 2%.The barometric height of mercury

1. Increases by 2%
2. Decreases by 2%
3. Remains unchanged
4. Sometimes increases and sometimes decreases

Answer: 1. Increases by 2%

Question 8. A barometer kept in a stationary elevator reads 76 cm. If the elevator starts accelerating the reading will be

1. Zero
2. Equal to 76 cm
3. More than 76 cm
4. Less than 76 cm

Answer: 4. Less than 76 cm

Question 9. A beaker containing a liquid is kept inside a big closed jar. If the air inside the jar is continuously pumped out, the pressure in the liquid near the bottom of the liquid will

1. Increases
2. Decreases
3. Remain constant
4. First decrease and then increase

Answer: 2. Decreases

Question 10. A vertical U-tube of the uniform inner cross-section contains mercury on both sides of its arms. A glycerin (density =1.3g/cm³)column of length 10cm is introduced into one of its arms. Oil of density 0.8 gm/cm³ is poured into the other arm until the upper surfaces of the oil and glycerin are at the same horizontal level. Find the length of the oil column, Density of mercury = 13.6 g/cm³

1. 10.4cm
2. 8.2 cm
3. 7.2cm
4. 9.6cm

Answer: 4. 9.6cm

Question 11. From the adjacent figure, the correct observation is

1. The pressure on the bottom of the tank is greater than at the bottom of (2).
2. The pressure on the bottom of the tank is smaller than at the bottom of
3. The pressure depends on the shape of the container
4. The pressure on the bottom of and is the same

Answer: 4. The pressure on the bottom of and is the same

Question 12. Air is blown through a hole in a closed pipe containing liquid. Then the pressure will

1. Increase on sides
2. Increase downwards
3. Increase in all direction
4. Never increases

Answer: 4. Never increases

Question 13. The radius of an air bubble at the bottom of the lake is r and it becomes 2r when the air bubbles rise to the top surface of the lake. If P cm water is the atmospheric pressure, then the depth of the lake is

1. 2p
2. 8p
3. 4p
4. 7p

Answer: 4. 7p

Question 14. A closed rectangular tank is completely filled with water and is accelerated horizontally with an acceleration towards the right. Pressure is

1. Maximum at, and
2. Minimum at

1. (1)B (2)D
2. (1)C (2)D
3. (1)B (2)C
4. (1)B (2)A

Answer: 1. (1)B (2)D

Question 15. A given-shaped glass tube having a uniform cross-section is filled with water and is mounted on a rotatable shaft as shown in the figure. If the tube is rotated with a constant angular velocity ω then

1. Water levels in both sections A and B go up
2. The water level in Section A goes up and that in B comes down
3. The water level in Section A comes down and in B it goes up
4. Water levels remain the same in both sections

Answer: 1. Water levels in both sections A and B go up

NEET Physics Chapter 5 Fluid Mechanics Multiple Choice Questions

Question 16. A siphon in use is demonstrated in the following figure. The density of the liquid flowing in the siphon is 1.5 gm/cc. The pressure difference between the points P and S will be

1. 10⁵ N/m
2. 2 × 10⁵ N/m
3. Zero
4. Infinity

Answer: 3. Zero

Question 17. Figure here shows the vertical cross-section of a vessel filled with a liquid of density ρ. The normal thrust per unit area on the walls of the vessel at point. P, as shown, will be

1. h ρ g
2. H ρ g
3. (H – h) ρ g
4. (H – h) ρ g cosθ

Answer: 3. (H – h) ρ g

Question 18. A tank with a length of 10 m, breadth of 8m, and depth of 6m is filled with water to the top. If g = 10 m s^-2 and the density of water is 1000 kg m^-3, then the thrust on the bottom is

1. 6 × 1000 × 10 × 80 N
2. 3 × 1000 × 10 × 48 N
3. 3 × 1000 × 10 × 60 N
4. 3 × 1000 × 10 × 80 N

Answer: 1. 6 × 1000 × 10 × 80 N

Question 19. In a hydraulic lift, used at a service station the radius of the large and small piston are in the ratio of 20:1. What weight placed on the small piston will be sufficient to lift a car of mass 1500 kg?

1. 3.75 kg
2. 37.5 kg
3. 7.5 kg
4. 75 kg.

Answer: 1. 3.75 kg

Question 20. Two vessels A and B of different shapes have the same base area and are filled with water up to the same height h (see figure). The force exerted by water on the base is F_A for vessel A and F_B for vessel B. The respective weights of the water-filled vessels are W_A and W_B. Then

1. F_A> F_B ; W_A> W_B
2. F_A= F_B ; W_A> W_B
3. F_A= F_B ; W_A< W_B
4. F_A> F_B ; W_A= W_B

Answer: 2. F_A= FB ; W_A> W_B

Question 21. A hydrogen balloon released on the moon would:

1. Climb up with an acceleration of 9.8 m/s²
2. Climb up with an acceleration of 9.8 × 6 m/s²
3. Neither climb nor fall
4. Fall with an acceleration of 9.8/6 m/s²

Answer: 4. Fall with an acceleration of 9.8/6 m/s²

Question 22. Reason for weightlessness in satellite :

1. Zero gravity
2. Centre of gravity
3. Zero reaction force on a plane of the satellite
4. None of these

Answer: 3. Zero reaction force on a plane of the satellite

Question 22. A hemispherical bowl just floats without sinking in a liquid of density 1.2 × 10³ kg/m³. If the outer diameter and the density of the bowl are 1 m and 2 × 10⁴ kgm³ respectively, then the inner diameter of the bowl will be

1. 0.94 m
2. 0.97 m
3. 0.98 m
4. 0.99 m

Answer: 3. 0.98 m

Question 23. In making an alloy, a substance of specific gravity s₁ and mass m₁ is mixed with another substance of specific gravity s₂ and mass m₂; then the specific gravity of the alloy is

1. \(\left(\frac{m_1+m_2}{s_1+s_2}\right)\)
2. \(\left(\frac{\mathrm{s}_1 \mathrm{~s}_2}{\mathrm{~m}_1+\mathrm{m}_2}\right)\)
3. \(\frac{m_1+m_2}{\left(\frac{m_1}{s_1}+\frac{m_2}{s_2}\right)}\)
4. \(\frac{\left(\frac{m_1}{s_1}+\frac{m_2}{s_2}\right)}{m_1+m_2}\)

Answer: 3. \(\frac{m_1+m_2}{\left(\frac{m_1}{s_1}+\frac{m_2}{s_2}\right)}\)

Question 24. Two solids A and B float in water. It is observed that A floats with half its volume immersed and B floats with 2/3 of its volume immersed. Compare the densities of A and B

1. 4 :3
2. 2 :3
3. 3:4
4. 1 :3

Answer: 4. 1 :3

Question 25. A body is just floating on the surface of a liquid. The density of the body is the same as that of the liquid. The body is slightly pushed down. What will happen to the body?

1. It will slowly come back to its earlier position position
2. It will remain submerged, where it is left
3. It will sink
4. It will come out violently

Answer: 2. It will remain submerged, where it is left

Question 26. A rectangular block is 5 cm × 5 cm × 10 cm in size. The block is floating in water with a 5 cm side vertical. If it floats with a 10 cm side vertical, what change will occur in the level of water?

1. No change
2. It will rise
3. It will fall
4. It may rise or fall depending on the density of a block

Answer: 1. No change

Question 27. A boat carrying steel balls is floating on the surface of water in a tank. If the balls are thrown into the tank one by one how will it affect the level of water

1. It will remain unchanged
2. It will rise
3. It will fall
4. First, it will first rise and then fall

Answer: 3. It will fall

Question 28. Two pieces of metal when immersed in a liquid have equal upthrust on them; then

1. Both pieces must have equal weights
2. Both pieces must have equal densities
3. Both pieces must have equal volumes
4. Both are floating to the same depth

Answer: 3. Both pieces must have equal volumes

Question 29. A wooden cylinder floats vertically in water with half of its length immersed. The density of wood is

1. Equal to that of water
2. Half the density of water
3. Double the density of water
4. The question is incomplete

Answer: 2. Half the density of water

Question 30. An ice block contains a glass ball when the ice melts within the water, the level of water

1. Rises
2. Falls
3. Unchanged
4. First rises and then falls

Answer: 2. Falls

Fluid Mechanics NEET Class 11 MCQs with Detailed Solutions

Question 31. The construction of submarines is based on

1. Archimedes’ principle
2. Bernoulli’s theorem
3. Pascal’s law
4. Newton’s laws

Answer: 1. Archimedes’ principle

Question 32. A concrete sphere of radius R has a cavity of radius r which is packed with sawdust. The specific gravities of concrete and sawdust are respectively 2.4 and 0.3 for this sphere to float with its entire volume submerged under water. The ratio of the mass of concrete to the mass of sawdust will be

1. 8
2. 4
3. 3
4. Zero

Answer: 2. 4

Question 33. A cubical block is floating in a liquid with half of its volume immersed in the liquid. When the whole system accelerates upwards with an acceleration of g/3, the fraction of volume immersed in the liquid will be

1. \(\frac{1}{2}\)
2. \(\frac{3}{8}\)
3. \(\frac{2}{3}\)
4. \(\frac{3}{4}\)

Answer: 1. \(\frac{1}{2}\)

Question 34. A silver ingot weighing 2.1 kg is held by a string so as to be completely immersed in a liquid of relative density 0.8. The relative density of silver is 10.5. The tension in the string in kg-wt is

1. 1.6
2. 1.94
3. 3.1
4. 5.25

Answer: 2. 1.94

Question 35. A solid sphere of density η ( > times lighter than water is suspended in a water tank by a string. If the mass of the sphere is m then the tension in the string is given by

1. \(\left(\frac{\eta-1}{\eta}\right) \mathrm{mg}\)
2. ηmg
3. \(\frac{\mathrm{mg}}{\eta-1}\)
4. (η−1)mg

Answer: 4. (η−1)mg

Question 36. A hollow sphere of volume V is floating on a water surface with half immersed in it. What should be the minimum volume of water poured inside the sphere so that the sphere now sinks into the water?

1. V/2
2. V/3
3. V/4
4. V

Answer: 1. V/2

Question 37. Two solids A and B float in water. It is observed that A floats with half its volume immersed and B floats with 2/3 of its volume immersed. Compare the densities of A and B

1. 4 : 3
2. 2 : 3
3. 3: 4
4. 1 : 3

Answer: 3. 3: 4

Question 38. The fraction of a floating object of volume V₀ and density d₀ above the surface of a liquid of density d will be

1. \(\frac{d_0}{d}\)
2. \(\frac{\mathrm{dd}_0}{\mathrm{~d}+\mathrm{d}_0}\)
3. \(\frac{d-d_0}{d}\)
4. \(\frac{\mathrm{dd}_0}{\mathrm{~d}-\mathrm{d}_0}\)

Answer: 3. \(\frac{d-d_0}{d}\)

Question 39. The density of the ice is ρ and that of water is σ. What will be the decrease in volume when a mass M of ice melts?

1. \(\frac{M}{\sigma-\rho}\)
2. \(\frac{\sigma-\rho}{M}\)
3. \(M\left[\frac{1}{\rho}-\frac{1}{\sigma}\right]\)
4. \(\frac{1}{\mathrm{M}}\left[\frac{1}{\rho}-\frac{1}{\sigma}\right]\)

Answer: 3. \(M\left[\frac{1}{\rho}-\frac{1}{\sigma}\right]\)

Question 40. The reading of a spring balance when a block is suspended from it in the air is 60 newton. This reading is changed to 40 newtons when the block is submerged in water. The specific gravity of the block must be therefore :

1. 3
2. 2
3. 6
4. 3/2

Answer: 1. 3

Question 41. A block of steel of size 5 cm × 5 cm × 5 cm is weighed in water. If the relative density of steel is 7. Its apparent weight is :

1. 6 × 5 × 5 × 5 gf
2. 4 × 4 × 4 × 7 gf
3. 5 × 5 × 5 × 7 gf
4. 4 × 4 × 4 × 6 gf

Answer: 1. 6 × 5 × 5 × 5 gf

Question 42. Two bodies are in equilibrium when suspended in water from the arms of a balance. The mass of one body is 36 g and its density is 9 g/cc. If the mass of the other is 48 g, its density in g/cc is :

1. 4/3
2. 3/2
3. 3
4. 5

Answer: 3. 3

Question 43. In order for a floating object to be in a stable rotation at equilibrium, its center of buoyancy should be

1. Vertically above its center of gravity
2. Vertically below its center of gravity
3. Horizontally in line with its center of gravity
4. May be anywhere

Answer: 1. Vertically above its center of gravity

Question 44. A cork is submerged in water by a spring attached to the bottom of a bowl. When the bowl is kept in an elevator moving with acceleration downwards, the length of the spring

1. Increases
2. Decreases
3. Remains unchanged
4. None of these

Answer: 2. Decreases

Question 45. A hollow sphere of volume V is floating on a water surface with half immersed in it. What should be the minimum volume of water poured inside the sphere so that the sphere now sinks into the water?

1. V/2
2. V/3
3. V/4
4. V

Answer: 1. V / 2

Question 46. An ice block contains a glass ball when the ice melts within the water-containing vessel, the level of water

1. Rises
2. Falls
3. Unchanged
4. First rises and then falls

Answer: 2. Falls

Question 47. A large ship can float but a steel needle sinks because of

1. Viscosity
2. Surface tension
3. Density
4. None of these

Answer: 4. None of these

Question 48. An iceberg of density 900 kg/m³ is floating in water of density 1000 Kg/m³. The percentage of the volume of ice-cube outside the water is

1. 20%
2. 35%
3. 10%
4. 25%

Answer: 3. 10%

Question 49. A hemispherical portion of radius R is removed from the bottom of a cylinder of radius R. The volume of the remaining cylinder is V and its mass M. It is suspended by a string in a liquid of density ρ where it stays vertical. The upper surface of the cylinder is at a depth h below the liquid surface. The force on the bottom of the cylinder by the liquid is:

1. Mg
2. Mg – Vρg
3. Mg + πR²hρg
4. ρg(V + πR²h)

Answer: 4. ρg(V + πR²h)

NEET Class 11 Fluid Mechanics MCQs for Exam Preparation

Question 50. A wooden block with a coin placed on its top floats in water as shown in the figure. The distance and h are shown here. After some time the coin falls into the water. Then

1. l decreases and h increase
2. l increases and h decreases
3. Both l and h increases
4. Both l and h decrease

Answer: 4. Both l and h decrease

Question 51. If a sphere is inserted in water, then it flows with \(\frac{1}{3}\) rd of it outside the water, When it is inserted in an unknown liquid then it flows with \(\frac{3}{4}\) th of it outside, then the density of the unknown liquid is:

1. 4.9 gm/c.c
2. \(\frac{9}{4}\) gm/c.c
3. \(\frac{8}{3}\) gm/c.c
4. \(\frac{3}{8}\) gm/c.c

Answer: 3. \(\frac{8}{3}\) gm/c.c

Question 52. A body of uniform cross-sectional area floats in a liquid of density thrice its value. The fraction of exposed height will be:

1. \(\frac{2}{3}\)
2. \(\frac{5}{6}\)
3. \(\frac{1}{6}\)
4. \(\frac{1}{3}\)

Answer: 1. \(\frac{2}{3}\)

Question 53. A raft of wood of mass 120 kg floats in water. The weight that can be put on the raft to make it just sing, should be : (draft = 600 kg/m³)

1. 80 kg
2. 50 kg
3. 60 kg
4. 30 kg

Answer: 1. 80 kg

Question 54. A rectangular block of mass m and area of cross-section A floats in a liquid of density ρ. If it is given a small vertical displacement from equilibrium it undergoes oscillation with a time period T. Them :

1. \(\mathrm{T} \propto \sqrt{\rho}\)
2. \(\mathrm{T} \propto \frac{1}{\sqrt{\mathrm{A}}}\)
3. \(T \propto \frac{1}{\rho}\)
4. \(\mathrm{T} \propto \frac{1}{\sqrt{\mathrm{m}}}\)

Answer: 2. \(\mathrm{T} \propto \frac{1}{\sqrt{\mathrm{A}}}\)

Question 55. The bob of a simple pendulum executes simple harmonic motion in water with a period t, while the period of oscillation of the bob is t₀ in air. Neglecting the frictional force of water and given that the density of the bob is (4/3)× 1000 kg/m³. What relationship between t and t₀ is true?

1. t = t₀
2. t = t₀/2
3. t = 2t₀
4. t = 4t₀

Answer: 3. t = 2t₀

Question 56. A jar is filled with two non-mixing liquids 1 and 2 having densities ρ₁ and ρ₂, respectively. A solid ball, made of a material of density ρ₃, is dropped in the jar. It comes to equilibrium in the position shown in the figure.

Which of the following is true for ρ₁, ρ₂ and ρ₃?

1. ρ₁> ρ₃> ρ₂
2. ρ₁< ρ₂< ρ₃
3. ρ₁< ρ₃< ρ₂
4. ρ₃< ρ₁< ρ₂

Answer: 3. ρ₁< ρ₃< ρ₂

Question 57. A ball is made of a material of density ρ where ρoil < ρ < ρwater with ρoil and ρwater representing the densities of oil and water, respectively. The oil and water are immiscible. If the above ball is in equilibrium in a mixture of this oil and water, which of the following pictures represents its equilibrium position?

Answer: 2

Question 58. A block of volume V and of density σb is placed in a liquid of density σ_l (σ_l > σ_b), then the block is moved upward upto a height h and it is still in the liquid. The increase in gravitational potential energy of the system is :

1. σ_b Vgh
2. (σ_b + σ_l)Vgh
3. (σ_b – σ_l)Vgh
4. None of these

Answer: 3. (σ_b – σ_l)Vgh

Question 59. A metallic sphere floats (just sink) in an immiscible mixture of water (_ρw = 103 kg/mand a liquid (_ρL= 13.5 × 10 with (1/5)th portion by volume in the liquid. The density of the metal is :

1. 4.5 × 10³ kg/m³
2. 4.0 × 10³ kg/m³
3. 3.5 × 10³ kg/m³
4. 1.9 × 10³ kg/m³

Answer: 3. 3.5 × 10³ kg/m³

Question 60. Three liquids of densities d, 2d, and 3d are mixed in equal volumes. Then the density of the mixture is

1. d
2. 2d
3. 3d
4. 5d

Answer: 2. 2d

Question 61. Three liquids of densities d, 2d, and 3d are mixed in equal proportions of weights. The relative density of the mixture is

1. \(\frac{11 d}{7}\)
2. \(\frac{18 d}{11}\)
3. \(\frac{13 d}{9}\)
4. \(\frac{23 d}{18}\)

Answer: 2. \(\frac{18 d}{11}\)

Question 62. Figure shows a weigh-bridge, with a beaker P with water on one pan and a balancing weight R on the other. A solid ball Q is hanging with a thread outside the water. It has a volume of 40 cm³ and weighs 80 g. If this solid is lowered to sink fully in water, but not touching the beaker anywhere, the balancing weight R’ will be

1. Same as R
2. 40 g less than R
3. 40 g more than R
4. 80 g more than R

Answer: 3. 40 g more than R

Question 63. In which one of the following cases will the liquid flow in a pipe be most streamlined

1. Liquid of high viscosity and high density flowing through a pipe of small radius
2. Liquid of high viscosity and low density flowing through a pipe of small radius
3. Liquid of low viscosity and low density flowing through a pipe of large radius
4. Liquid of low viscosity and high density flowing through a pipe of large radius

Answer: 2. Liquid of high viscosity and low density flowing through a pipe of small radius

Fluid Mechanics Multiple Choice Questions for NEET Physics Class 11

Question 64. Two water pipes of diameters 2 cm and 4 cm are connected with the main supply line. The velocity of the flow of water in the pipe of 2 cm diameter is

1. 4 times that in the other pipe
2. 14 times than in the other pipe
3. 2 times that in the other pipe
4. 12 times than in the other pipe

Answer: 1. 4 times that in the other pipe

Question 65. Water enters through end A with speed υ1 and leaves through end B with speed υ2 of a cylindrical tube AB. The tube is always completely filled with water. In case I tube is horizontal in case II it is vertical with end A upwards and in case III it is vertical with end B upwards. We have υ₁ = υ₂ for

1. Case 1
2. Case 2
3. Case 3
4. Each case

Answer: 4. Each case

Question 66. Water is moving with a speed of 5.18 ms^-1 through a pipe with a cross-sectional area of 4.20 cm². The water gradually descends 9.66 m as the pipe increases in area to 7.60 cm2. The speed of flow at the lower level is

1. 3.0 ms^-1
2. 5.7 ms^-1
3. 3.82 ms^-1
4. 2.86 ms^-1

Answer: 4. 2.86 ms^-1

Question 67. In the following flag. Is shown the flow of liquid through a horizontal pipe. Three tubes A, B, and C are connected to the pipe. The radii of tubes A, B, and c at the junction are respectively 2 cm, 1 cm, and 2cm. It can be said that the

1. The height of the liquid in tube A is the maximum
2. Height of the liquid in the tubes A and B is the same
3. The height of the liquid in all three tubes is the same
4. Height of the liquid in the tubes A and C is the same

Answer: 4. Height of the liquid in the tubes A and C is the same

Question 68. Air is steaming past a horizontal airplane wing such that its speed is 120 m/s over the upper surface and 90 m/s at the lower surface. If the density of air is 1.3 kg per metre3 and the wing is 10 m long and has an average width of 2 m, then the difference of the pressure on the two sides of the wing of

1. 4095.0 Pascal
2. 409.50 Pascal
3. 40.950 Pascal
4. 4.0950 Pascal

Answer: 1. 4095.0 Pascal

Question 69. A cylinder of height 20 m is filled with water. The velocity of efflux of water (in m/s) through a small hole on the side wall of the cylinder near its bottom is

1. 10
2. 20
3. 25.5
4. 5

Answer: 2. 20

Question 70. There is a hole in the bottom of the tank having water. If the total pressure at the bottom is 3 atm (1 atm = 10⁵ N/mthen the velocity of water flowing from the hole is

1. \(\sqrt{400} \mathrm{~m} / \mathrm{s}\)
2. \(\sqrt{600} \mathrm{~m} / \mathrm{s}\)
3. \(\sqrt{60} \mathrm{~m} / \mathrm{s}\)
4. None of these

Answer: 1. \(\sqrt{400} \mathrm{~m} / \mathrm{s}\)

Question 71. In a turbulent flow, the velocity of the liquid molecules in contact with the walls of the tube is

1. Zero
2. Maximum
3. Equal to critical velocity
4. May have any value

Answer: 4. May have any value

Question 72. Water is flowing through a tube of non-uniform cross-section ratio of the radius at the entry and exit end of the pipe is 3: 2. Then the ratio of velocities at the entry and exit of liquid is

1. 4: 9
2. 9: 4
3. 8: 27
4. 1: 1

Answer: 1. 4: 9

Fluid Mechanics MCQ Practice Test with Answers for NEET Class 11

Question 73. Water is flowing through a horizontal pipe of non-uniform cross-section. At the extremely narrow portion of the pipe, the water will have

1. Maximum speed and least pressure
2. Maximum pressure and least speed
3. Both pressure and speed maximum
4. Both pressure and speed least

Answer: 1. Maximum speed and least pressure

Question 74. A liquid flows in a tube from left to right as shown in the figure. A₁ and A₂ are the cross-sections of the portions of the tube as shown. Then the ratio of speeds ν₁/ ν₂ will be

1. A₁/ A₂
2. A₂/ A₁
3. \(\sqrt{A_2} / \sqrt{A_1}\)
4. \(\sqrt{A_1} / \sqrt{A_2}\)

Answer: 2. A₂/ A₁

Question 75. A large tank filled with water to a height of ‘h’ is to be emptied through a small hole at the bottom. The ratio of time taken for the level of water to fall from h to \(\frac{h}{2}\) and from \(\frac{h}{2}\) to zero is

1. \(\sqrt{2}\)
2. \(\frac{1}{\sqrt{2}}\)
3. \(\sqrt{2}-1\)
4. \(\frac{1}{\sqrt{2}-1}\)

Answer: 3. \(\sqrt{2}-1\)

Question 76. There is a hole in area A at the bottom of the cylindrical vessel. Water is filled up to a height of h and water flows out in t second. If water is filled to a height of 4h, it will flow out in time equal to

1. t
2. 4t
3. 2 t
4. t/4

Answer: 3. 2 t

Question 77. In this figure, an ideal liquid flows through the tube, which is of uniform cross-section. The liquid has velocities v_A and v_B, and pressure P_A and P_B at points A and B respectively

1. v_A = v_B
2. v_B > v_A
3. P_A = P_B
4. P_B > P_A

Answer: (1,4)

Question 78. A liquid flows through a horizontal tube. The velocities of the liquid in the two sections, which have areas of cross-section A₁ and A₂, are v₁ and v₂ respectively. The difference in the levels of the liquid in the two vertical tubes is h

1. The volume of the liquid flowing through the tube in unit time is A₁v₁
2. \(v_2-v_1=\sqrt{2 g h}\)
3. \(v_2^2-v_1^2=2 g h\)
4. The energy per unit mass of the liquid is the same in both sections of the tube

Answer: (1,3,4)

Question 79. An L-shaped glass tube is just immersed in flowing water such that its opening is pointing against flowing water. If the speed of the water current is v, then

1. The water in the tube rises to height \(\frac{v^2}{2 \mathrm{~g}}\)
2. The water in the tube rises to height \(\frac{\mathrm{g}}{2 \mathrm{v}^2}\)
3. The water in the tube does not rise at all
4. None of these

Answer: 1. The water in the tube rises to height \(\frac{v^2}{2 \mathrm{~g}}\)

Question 80. A streamlined body falls through the air from a height of h on the surface of a liquid. If d and D(D > d) represent the densities of the material of the body and liquid respectively, then the time after which the body will be instantaneously at rest is

1. \(\sqrt{\frac{2 h}{g}}\)
2. \(\sqrt{\frac{2 h}{g} \cdot \frac{D}{d}}\)
3. \(\sqrt{\frac{2 h}{g} \cdot \frac{d}{D}}\)
4. \(\sqrt{\frac{2 h}{g}}\left(\frac{d}{D-d}\right)\)

Answer: 4. \(\sqrt{\frac{2 h}{g}}\left(\frac{d}{D-d}\right)\)

Question 81. A large tank is filled with water to a height of H. A small hole is made at the base of the tank. It takes T₁ time to decrease the height of water to \(\frac{H}{\eta}(\eta>1)\), and it takes T₂ time to take out the rest of the water. T₁ = T₂ then the value of η is

1. 2
2. 3
3. 4
4. \(2 \sqrt{2}\)

Answer: 3. 4

Question 82. Bernoulli’s principle is based on the law of conservation:

1. Mass
2. Momentum
3. Energy
4. None of these

Answer: 3. Energy

Question 83. The action of the paint gun is based on:

1. Bernoulli’s principle
2. Boyle’s law
3. Faraday’s law
4. Archimedes principle

Answer: 1. Bernoulli’s principle

NEET Physics Chapter 5 Fluid Mechanics MCQs: Key Concepts and Solutions

Question 84. Bernoulli’s equation is applicable to points:

1. In a steadily flowing liquid
2. In a streamlined
3. In a straight line perpendicular to a streamline
4. For ideal liquid streamline flow on a streamline

Answer: 4. For ideal liquid streamline flow on a streamline

Question 85. Bernoulli’s equation is based upon:

1. Isochoric process
2. Isobaric process
3. Isothermal process
4. Adiabatic process

Answer: 3. Isothermal process

Question 86. The horizontal flow of fluid depends upon

1. Pressure difference
2. Amount of fluid
3. Density of fluid
4. All the above

Answer: 1. Pressure difference

Question 87. In steady horizontal flow:

1. The pressure is greatest where the speed is least
2. The pressure is independent of speed
3. The pressure is the least where the speed is the least
4. (1) and (3) are correct

Answer: 1. The pressure is greatest where the speed is least

Question 88. In a laminar flow, the velocity of the liquid in contact with the walls of the tube is

1. Zero
2. Maximum
3. In between zero and maximum
4. Equal to critical velocity

Answer: 1. Zero

Question 89. In a turbulent flow, the velocity of the liquid molecules in contact with the walls of the tube is –

1. Zero
2. Maximum
3. Equal to critical velocity
4. May have any value

Answer: 4. May have any value

Question 90. The Reynolds number of a flow is the ratio of

1. Gravity to viscous force
2. Gravity force to pressure force
3. Inertia forces to viscous force
4. Viscous forces to pressure forces

Answer: 3. Inertia forces to viscous force

Question 91. A tank is filled with water up to height H. Water is allowed to come out of a hole P in one of the walls at a depth D below the surface of the water. Express the horizontal distance x in terms of H and D :

1. \(x=\sqrt{D(H-D)}\)
2. \(x=\sqrt{\frac{D(H-D)}{2}}\)
3. \(x=2 \sqrt{D(H-D)}\)
4. \(x=4 \sqrt{D(H-D)}\)

Answer: 3. \(x=2 \sqrt{D(H-D)}\)

Fluid Mechanics MCQs for NEET Class 11: Complete Question Bank

Question 92. A fixed cylindrical vessel is filled with water up to height H. A hole is bored in the wall at a depth of h from the free surface of the water. For maximum horizontal range, h is equal to :

1. H
2. 3H/4
3. H/2
4. H/4

Answer: 3. H/2

Question 93. An incompressible liquid flows through a horizontal tube as shown in the figure. Then the velocity ‘ v ‘ of the fluid is :

1. 3.0 m/s
2. 1.5 m/s
3. 1.0 m/s
4. 2.25 m/s

Answer: 3. 1.0 m/s

Question 94. For a fluid that is flowing steadily, the level in the vertical tubes is best represented by

Answer: 1

Question 95. Water flows through a frictionless duct with a cross-section varying as shown in the figure. Pressure p at points along the axis is represented by

Answer: 1

Question 96. Air is blown through a hole in a closed pipe containing liquid. Then the pressure will :

1. Increase on sides
2. Increase downwards
3. Increase in all directions
4. Never increases

Answer: 3. Increase in all directions

Question 97. The Working of an atomizer depends upon

1. Bernoulli’s theorem
2. Boyle’s law
3. Archimedes principle
4. Newton’s law of motion

Answer: 1. Bernoulli’s theorem

Question 98. A cylinder of height 20m is completely filled with water. The velocity of efflux of water (in ms–through a small hole on the side wall of the cylinder near its bottom, is :

1. 10
2. 20
3. 25.5
4. 5

Answer: 2. 20

Question 99. An application of Bernoulli’s equation for fluid flow is found in

1. Dynamic lift of an aeroplane
2. Viscosity meter
3. Capillary rise
4. Hydraulic press

Answer: 1. Dynamic lift of an aeroplane

Question 100. A large open tank has two holes in the wall. One is a square hole of side L at a depth y from the top and the other is a circular hole of radius R at a depth 4y from the top. When the tank is completely filled with water, the quantities of water flowing out per second from both holes are the same. Then radius R, is equal to :

1. \(\frac{\mathrm{L}}{\sqrt{2 \pi}}\)
2. 2 π L
3. L
4. \(\frac{L}{2 \pi}\)

Answer: 1. \(\frac{\mathrm{L}}{\sqrt{2 \pi}}\)

Question 101. Water is filled in a container upto height 3m. A small hole of area ‘a’ is punched in the wall of the container at a height of 52.5 cm from the bottom. The cross-sectional area of the container is A. If a/A = 0.1 then v² is : (where v is the velocity of water coming out of the hole) (g = 10 m/s²)

1. 50
2. 51
3. 48
4. 51.5

Answer: 1. 50

Question 102. Statement -1 

The stream of water flowing at high speed from a garden hose pipe tends to spread like a fountain when held vertically up but tends to narrow down when held vertically down.

Statement -2

In any steady flow of an incompressible fluid, the volume flow rate of the fluid remains constant.

1. Statement -1 is True, Statement -2 is True; Statement -2 is a correct explanation for Statement -1
2. Statement -1 is True, Statement -2 is True; Statement -2 is NOT a correct explanation for Statement -1
3. Statement -1 is True, Statement -2 is False
4. Statement -1 is False, Statement -2 is True.

Answer: 1. Statement -1 is True, Statement -2 is True; Statement -2 is a correct explanation for Statement -1

NEET Physics Chapter 5 Fluid Mechanics: Practice MCQs and Answers

Question 103. Water is flowing inside a tube of a uniform radius ratio of the radius of entry and exit terminals of the tube is 3: 2. Then the ratio of velocities at entry and exit terminals will be :

1. 4: 9
2. 9: 4
3. 8: 27
4. 1: 1

Answer: 1. 4: 9

Question 104. At what speed, the velocity head of water is equal to the pressure head of 40 cm of hg?

1. 10.3 m/s
2. 2.8 m/s
3. 5.6 m/s
4. 8.4 m/s

Answer: 1. 10.3 m/s

Question 105. A hole in the bottom of the tank has water. If the total pressure at the bottom is 3 atm (1 atm = 10⁵ Nm^-2), then the velocity of water flowing from the hole is :

1. \(\sqrt{400} \mathrm{~ms}^{-1}\)
2. \(\sqrt{600} \mathrm{~ms}^{-1}\)
3. \(\sqrt{60} \mathrm{~ms}^{-1}\)
4. None of these

Answer: 1. \(\sqrt{400} \mathrm{~ms}^{-1}\)

Question 106. The velocity of water flowing in a non-uniform tube is 20 cm/s at a point where the tube radius is 0.2 cm. The velocity at another point, where the radius is 0.1 cm is:

1. 80 cm/s
2. 40 cm/s
3. 20 cm/s
4. 5 cm/s

Answer: 1. 80 cm/s

Question 107. Water is poured into a vessel at a constant rate β m³/s. There is a small hole of area α at the bottom of the vessel. The maximum level of water in the vessel is proportional to

1. β/α
2. β²/α
3. β²/ α²
4. α²/ β²

Answer: 3. β²/ α²

Question 108. A manometer connected to a closed tap reads 3.5 × 10⁵ N/m², When the value is opened, the reading of the manometer falls to 3.0 × 10⁵ N/m², then the velocity of the flow of water is

1. 100 m/s
2. 10 m/s
3. 1 m/s
4. 1010m/s

Answer: 2. 10 m/s

Question 109. According to Bernoulli’s equation \(\frac{P}{p g}+h \frac{1}{2} \frac{v}{g}\)= Constant

The terms A, B, and C are generally called respectively :

1. Gravitational head, pressure head, and velocity head
2. Gravity, gravitational head, and velocity head
3. Pressure head, gravitational head, and velocity head
4. Gravity, Pressure, and velocity head

Answer: 3. Pressure head, gravitational head, and velocity head

NEET Physics Class 11 Chapter 5 Fluid Mechanics MCQs and Answers

Question 110. The weight of the sphere in the air is 50g. Its weight is 40 g in a liquid, at a temperature of 20°C. When the temperature increases to 70°C, it weight becomes 45 g. Find

1. The ratio of densities of liquid at given two temperatures,

Answer: \(\frac{\rho_1}{\rho_2}=\frac{2}{1}\) the ratio of densities of liquid at given two temperatures,

2. The coefficient of cubical expansion of liquid assumes that there is no expansion of the volume of a sphere.

Answer: \(\frac{1}{(70-20)}=0.02 /{ }^{\circ} \mathrm{C}\)

Question 111. The cubical container ABCDEFGH which is completely filled with an ideal (nonviscous and incompressible) fluid, moves in a gravity-free space with an acceleration of a = \(a_0(\hat{i}-\hat{j}+\hat{k})\) where a₀ is a positive constant. Then the only point in the container where pressure is maximum is

1. B
2. C
3. E
4. F

Answer: 1. B

Question 112. In the previous question pressure will be minimal at point –

1. A
2. B
3. H
4. F

Answer: 4. F

Question 113. A cylindrical tank of height 0.4 m is open at the top and has a diameter of 0.16 m. Water is filled in it up to a height of 0.16 m. how long it will take to empty the tank through a hole of radius 5×10^-3 m in its bottom?

1. 46.26 sec.
2. 4.6 sec.
3. 462.6 sec.
4. 4.46 sec.

Answer: 1. 46.26 sec.

Question 114. A narrow tube completely filled with a liquid is lying on a series of cylinders as shown in the figure. Assuming no sliding between any surfaces, the value of the acceleration of the cylinders for which liquid will not come out of the tube from anywhere is given by opening to the atmosphere

1. \(\frac{\mathrm{gH}}{2 \mathrm{~L}}\)
2. \(\frac{\mathrm{gH}}{\mathrm{L}}\)
3. \(\frac{2 \mathrm{gH}}{\mathrm{L}}\)
4. \(\frac{\mathrm{gH}}{\sqrt{2 \mathrm{~L}}}\)

Answer: 1. \(\frac{\mathrm{gH}}{2 \mathrm{~L}}\)

Question 115. A liquid is kept in a cylindrical vessel that is rotated along its axis. The liquid rises at the sides. If the radius of the vessel is 0.05 m and the speed of rotation is 2 rev/s, The difference in the height of the liquid at the center of the vessel and its sides will be (π² = 10) :

1. 3 cm
2. 2 cm
3. 3/2 cm
4. 2/3 cm

Answer: 2. 2 cm

Question 116. A container of liquid is released from the rest, on a smooth inclined plane as shown in the figure. The length of the inclined plane is sufficient, and assume liquid is finally in equilibrium. Finally liquid surface makes an angle horizontal.

1. 60º
2. 45º
3. 30º
4. None of these

Answer: 3. 30º

Question 117. A U-tube of base length “l” filled with the same volume of two liquids of densities ρ and 2ρ is moving with an acceleration “a” on the horizontal plane. If the height difference between the two surfaces (open to atmosphere) becomes zero, then the height h is given by:

1. \(\frac{\mathrm{a}}{2 \mathrm{~g}} \ell\)
2. \(\frac{3 \mathrm{a}}{2 \mathrm{~g}} \ell\)
3. \(\frac{\mathrm{a}}{\mathrm{g}} \ell\)
4. \(\frac{2 \mathrm{a}}{3 \mathrm{~g}} \ell\)

Answer: 2. \(\frac{3 \mathrm{a}}{2 \mathrm{~g}} \ell\)

Question 118. A given-shaped glass tube having a uniform cross-section is filled with water and is mounted on a rotatable shaft as shown in the figure. If the tube is rotated with a constant angular velocity ω then:

1. Water levels in both sections A and B go up
2. The water level in Section A goes up and that in B comes down
3. The water level in Section A comes down and in B it goes up
4. Water levels remain the same in both sections

Answer: 1. Water levels in both sections A and B go up

Question 119. A candle of diameter d is floating on a liquid in a cylindrical container of diameter D (D > > d) as shown in the figure. If it is burning at the rate of 2cm/hour then the top of the candle will

1. Remain at the same height
2. Fall at the rate of 1 cm/hour
3. Fall at the rate of 2 cm/hour
4. Go up the rate of 1 cm/hour

Answer: 2. Fall at the rate of 1 cm/hour

NEET Physics Class 11 Chapter 5 Fluid Mechanics MCQs and Answers

Question 120. There are two identical small holes on the opposite sides of a tank containing a liquid. The tank is open at the top. The difference in height between the two holes is h. As the liquid comes out of the two holes, the tank will experience a net horizontal force proportional to:

1. h^1/2
2. h
3. h^3/2
4. h²

Answer: 2. h

Question 121. The diagram shows a cup of tea seen from above. The tea has been stirred and is now rotating without turbulence. A graph showing the speed υ with which the liquid is crossing points at a distance X from O along a radius XO would look like

Answer: 4

Question 122. A wind with a speed of 40 m/s blows parallel to the roof of a house. The area of the roof is 250 m². Assuming that the pressure inside the house is atmospheric pressure, the force exerted by the wind on the roof and the direction of the direction of the force will be : (Pair = 1.2 kg / m³)

1. 4.8 x 10⁵ N, upwards
2. 2.4 x 10⁵ N, upwards
3. 2.4 x 10⁵ N, downwards
4. 4.8 x 10⁵ N, downwards

Answer: 2. 2.4 x 10⁵ N, upwards

Question 123. The heart of a man pumps 5 liters of through the arteries per minute at a pressure of 150 mm of mercury. If the density of mercury be 13.6 ×103 kg/m³ and g = 10m/s² then the power of heart in watt is:

1. 2.35
2. 3.0
3. 1.50
4. 1.70

Answer: 4. 1.70

Question 124. The cylindrical tube of a spray pump has radius, R, one end of which has n fine holes, each of radius r. If the speed of the liquid in the tube is V, the speed of the ejection of the liquid through the holes is:

1. \(\frac{\mathrm{VR}^2}{\mathrm{nr}^2}\)
2. \(\frac{V R^2}{n^3 r^2}\)
3. \(\frac{\mathrm{V}^2 \mathrm{R}}{\mathrm{nr}}\)
4. \(\frac{V R^2}{n^2 r^2}\)

Answer: 1. \(\frac{\mathrm{VR}^2}{\mathrm{nr}^2}\)

Question 125. Two non-mixing liquids of densities ρ and nρ (n > are put in a container. The height of each liquid is h. A solid cylinder of length L and density d is put in this container. The cylinder floats with its axis vertical and length pL (p < in the denser liquid. The density d is equal to

1. {1 + (n – 1)p}ρ
2. {1 + (n + 1)p}ρ
3. {2+(n + 1)p}ρ
4. {2 + (n – 1)p}ρ