Class 8 Science

NCERT Solutions For Class 8 Science Chapter 10 Sound LAQs

Question 1. The town hall building is situated close to Boojho’s house. There is a clock on the top of the town hall building that rings the bell every hour. Boojho has noticed that the sound of the clock appears to be much clearer at night. Explain
Answer:

We know that speed, pitch, and loudness are all initiated with a vibration. During the day, there are several vibrations around us. So, the sound coming from the clock gets disturbed, and the amplitude of vibrations becomes small.

But during the night, there are no such multiple vibrations in the environment. So, the sound is clearer. Further, the dew factor at night increases the speed of sound as the moisture level increases.

NCERT Class 8 Science Chapter 10 Sound LAQs

Question 2. An alarm bell is kept inside a vessel as shown in the figure. A person standing close to it can distinctly hear the sound of the alarm. Now, if the alt inside the vessel is removed completely, how will the loudness of the alarm be affected for the same person?

Answer:

Initially, the person can hear the sound coming from the air and water distinctly. But after some time, when the air is completely removed from the bottle, the sound will not pass through the vacuum in the glass. So, the man will not hear the sound that was coming through the air initially.

Question 3. How is sound produced, and how is it transmitted and heard by us? 
Answer:

Sound is produced when any object starts vibrating by any means.

These vibrations travel from the sources all around the environment through the particles, and thus they reach their destination, i.e., our ear.

Now, it enters our ear and travels down a canal at the end of which a thin membrane is stretched tightly, known as the eardrum. The eardrum sends vibrations to the inner part of the ear, and finally reaches the brain, and we hear the sounds.

NCERT Solutions for LAQs on Sound Chapter 10

Question 4. Mention the property of vibrations that determines the pitch of the sound. Briefly explain along with some examples.
Answer:

The property that determines the shrillness or pitch of a sound is the frequency. If the frequency of vibration is higher, then we can say that the sound has a higher pitch. If the frequency of vibration is lower, we can say that the sound has a lower pitch.

Example: The drum vibrates with a low frequency.

Thus, it produces a low-pitched sound. Besides this, a whistle has a high frequency that produces a sound of a higher pitch. A bird makes a high-pitched sound while a lion makes a low-pitched roar. However, the roar of a lion is very loud while the sound of a bird is quite feeble.

NCERT Solutions for Sound Chapter 10

Question 5. Kanika switched ON the television to listen to her favourite music. After some time, she heard a loudspeaker sound coming from her neighbour’s house. Then, she switched OFF the television and closed her ears, so that the loudspeaker sound would not enter her ears.

• Slate the type of sound coming from the television.
• Explain how Kanika can distinguish between the categories of sound
• Mention whether the sound coming from the TV and the loudspeaker was audible or inaudible.
• Give the value displayed by Kanika here.

Answer: The sound of the music was coming from the television.

She realised after hearing both the sounds that the sound coming from the TV is pleasant and that ling from the loudspeaker outside is noisy and painful.

The sound coming from the TV and loudspeakers was in audible range, i.e., 20 Hz to 20 kHz.

The value displayed by Kanika is an attraction towards music and a hatred towards the loudspeakers.

NCERT Solutions For Class 8 Science Chapter 10 Sound SAQs

Question 1. Boojho saw a cracker burst at night at a distance from his house. He heard the sound of the cracker a
little later after seeing the cracker burst. Give a reason for the delay in hearing the sound.
Answer:

The light travels faster than sound, so the light from the cracker reaches faster than the sound of the cracker. Speed oflight in air = 3 x 10 8 m/s Speed ofsound in air = 330 m/s

Question 2. Explain the reason for not hearing the screeches of a bat by us.
Answer:

As we know, the audible frequency range for human beings is 20 Hz to 20 kHz. So, it is an obvious thing that the frequency of bats is beyond this range, due to which we are usually unable to hear the screams of a bat.

NCERT Class 8 Science Chapter 10 Sound SAQs

Question 3. Suggest three measures to limit noise pollution in your locality.
Answer:

Some measures to limit noise pollution in our locality are given as

1. The industries that produce noise should be set up away from the residential areas.
2. The television and the music systems should be run at low volumes.
3. The aircraft engines, transport vehicles, industrial machines, and home appliances must be installed with silencing devices.

Question 4. List three sources of noise pollution in your locality.
Answer:

Sources of noise pollution are

1. Horns of vehicles
2. Loudspeakers of temples
3. Generators running without silencers

Question 5. Briefly explain total hearing impairment.
Answer:

Hearing impairment means a person has damaged hearing ability and cannot hear properly. Some people are born with poor hearing ability. A person with very poor hearing ability is said to be deaf, so deafness is a total hearing impairment.

NCERT Solutions for Sound Chapter 10

Question 6. The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the period of the vibration?
Answer:

Given, number of vibrations = 500

Time taken =ls

Period time taken/ number of vibrations

= 1/500= 0.002s

Question 7. Identify the part that vibrates to produce sound in the following instruments.

1. Dholak
2. Sitar
3. Flute

Answer:

Class 8 Chapter 10 Sound Short Answer Questions

Question 8. What is the difference between noise and music? Can music become noise sometimes?
Answer:

The Differences between noise and music are:

Question 9. List the sources of noise pollution in your surroundings.
Answer:

As we know that. Noise pollution is caused by excessive sound in our surroundings. The sources of such excessive sound are as follows

1. Television and transistor radio at high volume
2. Sounds of vehicles
3. Explosions, including the bursting of crackers, machines, loudspeakers, etc
4. Honking of horns

Question 10. Explain in what way noise pollution is harmful to humans.
Answer:

Lack of sleep, hypertension (high blood pressure), and temporary or permanent impairment of hearing are harmful effects of noise pollution.

NCERT Solutions for SAQs on Sound Chapter 10

Question 11. Your parents are going to buy a house. They have been offered one on the roadside and another three lanes from the roadside. Which house would you suggest your parents should buy? Explain your answer.
Answer:

We will suggest to our parents that they should buy a horn, which is three lanes away from the roadside. Taking a house on the roadside means bearing noise pollution, which leads to harmful effects on health.

Therefore, to attain a piece of mind and to avoid noise pollution, it is better to buy a house three lanes away from the roadside.

NCERT Solutions For Class 8 Science Chapter 8 Force And Pressure VSAQs

Question 1. Can you lift or push a book lying on a table without touching it?
Answer:

No, we cannot lift or push a book lying on a table without touching it because it is a type of contact force.

Question 2. What happens when you apply a force to an inflated balloon by pressing it between your palms?
Answer:

The shape of a balloon will change if we apply a force to an inflated balloon by pressing it between our palms.

Question 3. What does the force come from when we push an object like a school bag or lift a bucket of water?
Answer: This force is caused by the action of muscles in our body.

Question 4. List a few examples of the force exerted by the muscles in our body.
Answer: Chewing of food, lifting of luggage, and squeezing a sponge ball.

NCERT Class 8 Science Chapter 8 Force and Pressure VSAQs

Question 5. Leaves and fruits fall to the ground when they get detached from the plant. Have you ever wondered why it is so?
Answer:

Leaves and fruits fall towards the ground because Earth pulls them towards it, and this attractive force is known as the force of gravity or gravitational force.

Question 6. Is there any relation between pressure and force?
Answer:

Yes, pressure is force per unit area. Thus, we can say that pressure is directly proportional to force.

Question 7. Paheli wants to understand why porters place a round piece of cloth on their heads when they carry heavy loads.
Answer:

When a porter places a round piece of cloth on his head, it reduces the pressure on the head as the area ofcontact increases, and they find it easier to carry the load.

Question 8. Can you explain why shoulder bags are provided with broad straps and not thin straps?
Answer:

School bags are provided with broad straps because they increase the surface area of contact with the shoulder, which results in reducing the pressure on the shoulder.

NCERT Solutions for Force and Pressure Chapter 8

Question 9. Boojho has seen fountains of water coming out of the leaking joints or holes in pipes supplying water. Is it due to the pressure exerted by water on the walls of the pipes?
Answer:

Yes, water coming out of the leaking joints or holes in pipes supplying water is due to the pressure exerted by water on the surface of the pipes.

Question 10. Why is it easier to cut the fruit with a sharp knife as compared to a blunt knife?
Answer:

The surface area of a sharp knife is less than that of a blunt knife, so the pressure applied by a sharp knife is higher than blunt knife.

Question 11. In the following situation, identify the agent exerting the force and the object on which it acts. State the effect of the force in each case.

1. Squeezing a piece of lemon between the fingers to extract its juice.
2. Taking out paste from a toothpaste tube.
3. A load is suspended from a spring while its other end is on a hook fixed to a wall.
4. An athlete is making a high jump to clear the bar at a certain height.

Answer:

Force and Pressure VSAQs Class 8 NCERT Solutions

Question 12. A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?
Answer:

When a blacksmith hammers a hot piece of iron, the force due to hammering can change the shape of the piece of iron. In other words, we can say that the force applied through the hammer by the blacksmith can mould the hot piece of iron into any kind of tool.

Question 13. An inflated balloon was pressed against a wall after it had been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?
Answer:

As the balloon has been rubbed with a piece of synthetic cloth, it has acquired some electrostatic charge and become a charged body. Now, when this charged body (which is a balloon) is pressed against the wall, it will get attracted. Thus, the electrostatic force is responsible for the attraction between the balloon and the wall.

Question 14. Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.
Answer:

The forces acting on a plastic bucket are the gravitational force and the muscular force. These forces do not bring a change in its state of motion because, being equal and opposite in magnitude, the effect of the net force on the bucket becomes zero.

NCERT Solutions for VSAQs on Force and Pressure

Question 15. A rocket has been fired upwards to launch a satellite into orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.
Answer: Two forces are as follows:

1. Gravitational force
2. Friction due to air or the force of friction

Question 16. When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water fills the dropper. The rise of water in the dropper is due to

1. Pressure of water
2. Gravity of the Earth
3. Shape of rubber bulb
4. Atmospheric pressure

Answer: 4. Atmospheric pressure.

NCERT Solutions For Class 8 Science Chapter 8 Force And Pressure SAQs

Question 1. The figure shows a magnet at the top of a ramp and paper clips at the base of the ramp. He observed that the paper clip moved up the ramp and attached to the magnet. What forces were acting on the paper clip as it moved up the ramp?

Answer:

The paper clip moved up the ramp because it was attracted to the magnet, therefore, there was a magnetic force acting on it.

Gravitational and frictional forces also continue to act on the paper clip as it moves up the ramp.

NCERT Solutions for Force and Pressure SAQs Class 8

Question 2. A chapati maker is a machine that converts balls of dough into chapatis. What effect of force comes into play in this process?
Answer:

The force per unit area is called pressure, which works on the chapatis. This is the pressure that works on the dough balls and makes them chapatis with the help of a machine.

Question 3. Wooden or concrete sleepers are kept below the railway line. Explain why?
Answer:

Since the area on which the weight of the train acts increases which resulting in a decrease in the pressure on the ground which the train moves easily on the railway line without any risk of an accident. So, this is the reason for keeping the wooden or concrete below the railway line.

NCERT Solutions for Class 8 Science Force and Pressure SAQs

Question 4. Determine the pressure when a force of 200 N acts on the area

1. 20 m² and
2. 8m²

Answer:

⇒ \(\text { Pressure }=\frac{\text { Force }}{\text { Area }}\)

Given, F = 200N

For area, A=20m2

⇒ \(p=\frac{200}{20}=10 \mathrm{~N} / \mathrm{m}^2 \text { or } 10 \mathrm{~Pa}\)

⇒ \(p=\frac{200}{8}=25 \mathrm{~N} / \mathrm{m}^2 \text { or } 25 \mathrm{~Pa}\)

Question 5. Raman was very curious to know how the porters carry a heavy load on their heads easily. Suddenly, he asked his teacher, and the teacher told him that by reducing the pressure on the head, the porters can carry a heavy load.

1. Explain how the porters carry heavy loads easily.
2. Mention your views about Raman.

Answer:

The porters usually cover their heads with thick, round cloths before carrying the load. This increases the area ofcontact, therefore reducing pressure on the head. So, the porters carry a heavy load easily.

According to me, Raman is very curious to know about science.

NCERT Solutions for Force and Pressure Chapter 8 SAQs

Question 6. Two rods of the same weight and equal length have different thicknesses. They are held vertically on the surface of the sand as shown in the figure. Which one of them will sink more? Why?

Answer:

As we know, pressure exerted by the body is inversely proportional to the area where force is applied. So, the thinner rod, i.e., rod B, will sink more because it has less area of cross-section in contact with the surface, hence it will exert more pressure on the sand than rod A.

Question 7. What type of force is involved in each of the given conditions? Put a tick mark for the response in terms of push or pull.
Answer:

Force and Pressure Class 8 NCERT SAQs

Question 8. If the area of my head were 15 cm x 15 cm, how much force would air exert on my head?
Answer:

We know that. 1 atmospheric pressure =10 s N/m: = 10N/cm2

⇒ \(\text { Pressure }=\frac{\text { Force }}{\text { Area }}\)

Force = Pressure x Area =10x(15xl5) =2250 N.

Question 9. Give two examples each of situations in which you push or pull to change the state of motion of objects.
Answer:

The two examples are as follows:

1. We push the door open.
2. We pull a drawer to open it.

Force and Pressure SAQs NCERT Solutions Class 8

Question 10. Give two examples of situations in which applied force causes a change in the shape of an object.
Answer: The two examples are as follows:

• Spring: When we compress or stretch the spring, it changes its shape.
• Foam: When we compress the foam or sponge, it changes its shape.

NCERT Solutions For Class 8 Science Chapter 8 Force And Pressure Multiple Choice Questions

Question 1. Force due to the charged particles is known as

1. Muscular force
2. Magnetic force
3. Electrostatic force
4. Gravitational force

Answer: 3. Electrostatic force

Question 2. The pressure exerted by liquid due to an Increase In depth

1. Reduces
2. Increases
3. Remains same
4. Depends on the nature of the liquid

Answer: 2. Increases

NCERT Solutions for Force and Pressure MCQs Class 8

Question 3. Some mustard oil is kept in the beaker. It will exert pressure

1. Upward
2. Downward
3. Sideways
4. In all the directions

Answer: 4. In all the directions

Question 4. During dry weather, while combing hair, sometimes we experience hair flying apart. The force responsible for this is

1. Force of gravity
2. Electrostatic force
3. Force of friction
4. Magnetic force

Answer: 2. Electrostatic force

NCERT Solutions for Class 8 Science Force and Pressure MCQs

Question 5. Which one of the following forces is a contact force?

1. Force of gravity
2. Force of friction
3. Magnetic force
4. Electrostatic force

Answer: 2. Force of friction

Question 6. The standard value of atmospheric pressure is

1. 78 cm of Hg
2. 76 mm of Hg
3. 45 cm of Hg
4. 0.76 cm of Hg

Answer: 2 76 mm of Hg

NCERT Solutions for Force and Pressure Chapter 8 MCQs

Question 7. Two objects repel each other; this repulsion could be due to

1. Tractional force
2. Electrostatic force
3. Magnetic force
4. Either a magnetic or an electrostatic force

Answer: 3. Magnetic force

Question 8. How much pressure would be exerted by a block exerting 20 N of force on a 0.5 m 2 area?

1. 10N/m²
2. 20 N/m²
3. 30 N/m²
4. 40 N/m²

Answer: 4. 20 N/m²

Question 9. Which of these is an example of a contact force?

1. A guava falling from the tree.
2. A magnet attracts a hanging iron nail.
3. A plastic comb attracts small pieces of hair.
4. A boat moving on water by the action of wind on its sail.

Answer: 4. A boat moving on water by the action of wind on its sail.

Force and Pressure Class 8 NCERT MCQs

Question 10. Which of these is not true for force?

1. A force can change the state of motion of an object
2. A force can change the shape of an object
3. A force can act between two solid objects only
4. Forces applied on an object in the same direction add to one another.

Answer: 3. A force can act between two solid objects only

NCERT Solutions For Class 8 Science Chapter 5 Conservation Of Plants: Very Short Answer Questions

Question 1. Can a forest regenerate naturally in a short period?
Answer:

Restoration can take place naturally by leaving the drenched area undisturbed for a long period. During this period, the area re-establishes itself without the interference of human beings.

Question 2. Paheli is curious to know the purpose of making National Parks, Wildlife Sanctuaries, and Biosphere Reserves.
Answer:

National parks, Wildlife sanctuaries, and Biosphere reserves are made to protect the flora and fauna whose numbers are diminishing.

NCERT Class 8 Science Chapter 5 Conservation of Plants VSAQs

Question 3. Animal life is also affected by deforestation. How?
Answer:

The natural habitats of wild animals get destroyed due to deforestation, and they tend to move to other habitats or are left to die without proper shelter.

Question 4. List the factors disturbing the biodiversity of your area. Some of these factors and human activities may disturb the biodiversity unknowingly. List these human activities. How can these be checked?
Answer:

Various factors can disturb the biodiversity of an area, such as volcanic eruptions, earthquakes, thunderstorms, etc. Some human activities, such as deforestation pollution, poaching, etc., also destroy the biodiversity of an area. These human activities can be checked by educating people or applying strict laws.

Question 5. Paheli has heard that some of the endemic species may vanish. Is it true
Answer:

Yes, endemic species may vanish due to the destruction of their habitat, increasing population, and the introduction of new species.

NCERT Solutions for Conservation of Plants Chapter 5

Question 6. Boojho wants to know whether tigers are still found in the forest. He is excited to see a tiger.
Answer:

The Tiger is one of the many species that are slowly disappearing from forests. But the Satpura tiger reserve is unique in the sense that a significant increase in the population of tigers has been seen here.

Question 7. Pahcli wants to know whether only big animals are facing the danger of extinction.
Answer:

No, the small animals are much more in danger of becoming extinct than the bigger animals. This is because the small animals like snakes, frogs, etc., get killed ruthlessly without realising their importance in the ecosystem. They might be small in size, but their role in the ecosystem cannot be ignored.

NCERT Class 8 Science Chapter 9 Friction VSAQs

Question 1. Why is it difficult to move on a wet marble floor?
Answer: On a wot marble Door, the frictional force between the foot and Door decreases to make it slippery, thus we feel difficult to move on a wet wooden marble floor.

NCERT Solutions for Friction VSAQs Class 8

Question 2. State the reason why we slip when we step on a banana peel.
Answer: As we step on a banana peel, there is no grip between our foot and the banana peel due to very less friction. So, we slipped accidentally.

Question 3. Is the friction the same for all the surfaces?
Answer: No, because friction depends on the nature surface in contact.

Question 5. Can you imagine being able to walk at all if there were no friction?
Answer: No, we can’t walk at all if there is no friction.

Question 6. Could you write, if there were no friction between
Answer: No, we wouldn’t be able to write on a blackboard if there were no friction between the chalk and the board.

Question 7. How do you feel if you vigorously rub your palms together for a few minutes?
Answer: We will feel that our hands feel warm. This warmth is caused by a force called friction.

NCERT Solutions for Class 8 Science Friction VSAQs

Question 8. Have you ever thought why the sole of your shoe is grooved?
Answer: It is done to provide the shoes better grip. The groove on shoes increases the friction between the shoes and the floor.

Question 9. Why do you sprinkle fine powder on the carrom board?
Answer: Powder is sprinkled on the carrom board to reduce friction.

Question 10. The pieces of luggage were fitted with the rollers. Explain why?
Answer: To reduce friction, pieces of luggage are fitted with rollers so that even a child can pull the luggage easily.

NCERT Solutions for Friction Chapter 9 VSAQs

Question 11. Can we reduce friction to zero by polishing surfaces or using a large amount of lubricant?
Answer: No, friction can never be eliminated. Some irregularities are always there.

Question 12. Where do you think scientists got hints for the streamlined shapes?
Answer: Scientists got hints for the streamlined shapes from the body shapes of birds and fishes who have to move about in fluids all the time.

Question 13. Do you find any similarity in the shape of an aeroplane and that of a bird?
Answer: Yes, both have streamlined bodies, which help them to move easily through fluid.

NCERT Solutions For Class 8 Science Chapter 5 Conservation Of Plants SAQs

Question 1. Boojho wants to know if there is any permanent solution to the problem of deforestation.
Answer:

The permanent solution to the problem of deforestation is reforestation. It is the restocking of the destroyed forests by planting new trees.

Question 2. Difference between the following.

1. Wildlife sanctuary and Biosphere reserve
2. Zoo and Wildlife Sanctuary
3. Endangered and Extinct Species
4. Horn and Found

Answer:

1. The Difference between a wildlife sanctuary and a biosphere reserve is as follows:

NCERT Class 8 Science Chapter 5 Conservation of Plants SAQs

2. Differences between the zoo and a wildlife sanctuary are as follows

3. The difference between an endangered species and an extinct species is as follows

4. The difference between flora and fauna is as follows

NCERT Solutions for Conservation of Plants Chapter 5

Question 3. Discuss the effects of deforestation on the following.

1. Wild animals
2. Environment
3. Villages (rural areas)
4. Cities (urban areas)
5. Earth
6. The next generation

Answer:

1. Wild animals:

Deforestation destroys the habitat of wild animals. This leads them to the danger of extinction.

2. Deforestation:

Increases the amount of CO₂ in the environment, which increases the temperature. Due to this, the water cycle is disturbed, which may lead to drought. It also reduces the water holding capacity of soil, which leads to floods.

3. Villages (rural areas):

The lifestyle of villagers depends much on forests for wood, vegetables, fruits, meat, grass, etc. Deforestation leads their life to struggles for all of these. Also, their life become threatened by wild animals.

4. Cities (urban areas):

Deforestation causes drought, flooding, and environmental pollution, which affect the lives of people living in cities.

5. Earth:

The various gases on Earth, like water, oxygen, and carbon dioxide, are disturbed due to deforestation. It increases the temperature and pollution level on the Earth and is also the main cause of global warming.

6. The next generation:

The major effect of deforestation on the next generation is the limitation of natural resources like wood, oxygen, water, etc.

Conservation of Plants SAQs Class 8 NCERT Solutions

Question 4. What will happen if
Answer:

1. We go on cutting trees.
Answer:

If we continue cutting trees, then

1. Many animals will lose their shelters.
2. There would be a scarcity of materials like fruits, paper, which we get from forests.
3. Floods and droughts will become more frequent.
4. Earth will lose its most fertile layer and transform into a desert.

2. The habitat of an animal is disturbed.
Answer:

The habitat of an animal provides it with necessities such as shelter, food, and protection. If the habitat of an animal is disturbed, then it will be forced to go to other places in search of food and shelter. As a result, the animal could be killed.

3.  The top layer of soil is exposed.
Answer:

Removal of the top layer of the soil exposes the lower, hard, and rocky layers. This soil has less humus and is less fertile. Gradually, the fertile land gets converted into deserts. It is called desertification.

Question 5. Answer in brief.
Answer:

1. Why should we conserve biodiversity?
Answer:

We should conserve biodiversity because every organism in nature plays an important role in balancing of natural system.

2.  Protected forests are also not completely safe for wild animals. Why?
Answer:

Protected forests are not completely safe for wildlife because some local people kill animals on a large scale for their valuable skin, teeth, etc.

SAQs for Conservation of Plants Chapter 5 Class 8

3.  Some trials depend on the Jungle. How?
Answer:

Some tribals depend on the jungle because they get most of their resource to live from the jungle, like shelter, wood, food, etc.

4. What are the causes and consequences of deforestation?
Answer:

The main causes of deforestation are the cutting of trees for wood and the use of land for industries and houses. Its consequences are flooding, drought, extinction of species, and many more harmful activities.

5. What is the Red Data Book?
Answer:

The Red Data Book is a source book that maintains an international list of all endangered animals and plant species.

6. What do you understand by the term migration?
Answer:

Migration refers to the movement of an organism or a group oforganisms from its natural habitat to another place at a particular time because of climatic change. Birds that cover long distances to reach another land are known as migratory birds.

Question 6. To meet the ever-increasing demand in factories and for shelter, trees are being continually cut down. Is it justified to cut trees for such projects? Discuss and prepare a brief report.
Answer:

The continuous cutting of trees is not justified for any project because it leads to deforestation, desertification, flooding, and danger to the lives of wild animals. It also disturbs the balance of nature.

Question 7. How can you contribute to the development of the green wealth of your locality? Mnko, n list of notions to be taken by you.
Answer:

We can contribute to the maintenance of the green wealth of our locality by taking these actions.

1. Taking care of the plants and trees growing in or around the locality.
2. Encourage people to plant more trees by informing them about the importance of growing trees.

NCERT Solutions for SAQs on Conservation of Plants

Question 8. Find out about the National parks in your state. Identify and show their location on the outline map of India.

Answer:

One of the National parks located near Delhi is the Jim Corbett National Park in Uttarakhand.

Question 9. Why should paper be saved? Prepare a list of ways by which you can save paper.
Answer:

Paper should be saved because it takes our important natural resource, i.e., trees, to make it (around 17 full-grown trees to make one tonne of paper). Trees, as we know, are important to maintain a balance in nature.

Therefore, to save trees and prevent the impact of their loss in the living world, we need to save paper. We can save paper by following these ways

1. Paper should be recycled.
2. Use both sides of a paper for writing purposes.
3. Spread awareness regarding the value of saving paper.

NCERT Solutions For Class 8 Science Chapter 5 Conservation Of Plants Long Answer Question

Question 1. The Gangetic Dolphin is a freshwater aquatic mammal. Which of these measures will protect the Gangetic Dolphin species?

Circle ‘Yes’ or ‘No’ for the correct response

Answer: No, No, Yes

Question 2. The table shows an example of the different types of threats to the Gangetic Dolphin.

Surface runoffs containing pesticides also threaten the survival of the Gangetic Dolphin. Which type of threat in the table does this belong to? Explain your answer.

Answer:

Surface runoffs containing pesticides are an example of water pollution. Pesticides are harmful chemicals that pollute water bodies and threaten the survival of the Gangetic Dolphin.

NCERT Class 8 Science Chapter 5 Conservation of Plants LAQs

Question 3. The table shows two groups of natural resources.

1. Radha visited a protected forest area where she could enter at her own will and collect samples of herbs. Which type of protected forest area did Radha visit? Explain your answer.

Answer:

Radha visited wildlife sanctuary as in the wildlife sanctuary, where visitors are allowed without permission and can collect plant samples.

NCERT Solutions for Conservation of Plants Chapter 5

2. Which of these statements is supported by the table?

1. Mining is allowed in National parks
2. A zoo is an example of a wildlife sanctuary
3. National parks are larger than wildlife sanctuaries
4. Wildlife sanctuaries are always found in river basins

Answer: 3. National parks are larger than wildlife sanctuaries.

NCERT Class 8 Science Chapter 9 Friction Short Answer Questions

Question 1. Two friends are trying to push a heavy load as shown in figure below. Suggest a way which will make this task easier for them.

NCERT Solutions for Friction SAQs Class 8

Answer:

Both friends can put rollers below the heavy load. Since the rolling friction is smaller than the sliding friction. Therefore, putting rollers below the heavy load will make this task easier for them.

Question 2. It is easier to move the box from rest or to move it when it is already in motion. Explain why?
Answer:

When the object is at rest, we have to apply more force to overcome interlocking between irregularities. On the other hand, when the object starts moving, the contact points on its surface do not get enough time to lock into the contact points on the ground. So, it is easier to move the block when it is already in motion.

Question 3. Four children were asked to name forces due to rolling, static, and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement.

1. Rolling, static, sliding
2. Rolling, sliding, static
3. Static, sliding, rolling
4. Sliding, static, rolling

Answer:

3. We know that static friction is more powerful than all other frictions. Hence, it will take first place in decreasing order. Similarly, sliding friction is smaller than static friction but greater than rolling friction. Thus, the decreasing order of the forces due to these frictions is as follows

NCERT Solutions for Class 8 Science Friction SAQs

Static > Sliding > Rolling

Question 4. Alida runs her toy car on the dry marble floor, the wet marble floor, the newspaper, and a towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be

1. Wet marble floor, dry marble floor, newspaper, and towel
2. Newspaper, towel, dry marble floor, wet marble floor
3. Towel, newspaper, dry marble floor, wet marble floor
4. Wet marble floor, dry marble floor, towel, newspaper

Answer:

1. The correct arrangement is as follows:

Wet marble floor, dry marble floor, newspaper, and towel.

Question 5. Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of the frictional force acting on it.
Answer:

A book kept on a tilted writing desk starts sliding down. The direction frictional force is in the opposite direction, thus the frictional force will act in an upward direction.

Question 6. You spill a bucket of soapy water on a marble floor accidentally. Would it make it easier or more difficult for you to walk on the floor? Why?
Answer:

After spilling a bucket of soapy water on a marble floor, it would be more difficult for us to walk on the floor. Because the layer of soapy water reduces the friction and the foot cannot make a proper grip on the floor.

NCERT Solutions for Friction Chapter 9 SAQs

Question 7. Explain why sportsmon uao ahoea with splkea?
Answer:

Sportsmen use shoes with spikes in order to avoid slipping in the field. The spikes in the shoes increase the friction, so they can run on the ground easily.

Question 8. Iqbal has to push a lighter box, and Scema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?
Answer:

The heavy object will be pressed hard against the opposite surface and produce more friction. So, Secma will have to apply a larger force due to more friction.

Question 9. Explain why sliding friction is less than the static friction.
Answer:

We know that friction is caused by the interlocking of irregularities on the two surfaces.

In case of static friction, interlocking between two objects is very strong but in case ofsliding friction, there is less time ofgetting interlocked with each other. Thus, the sliding friction is less than the static friction.

NCERT Class 8 Science Chapter 9 Friction SAQs

Question 10. Give examples to show that friction is both a friend and a foe.
Answer:

Friction as a friend

1. It allows us to walk comfortably.
2. It allows us to minimise the speed or to stop the moving objects.
3. It allows us to write on a board with chalk.

Friction as a foe

1. It causes wear and tear in objects.
2. It causes damage to the parts of machines.
3. It does not allow the free movement of objects.

Friction Class 8 NCERT SAQs

Question 11. Explain why objects moving in fluids must have special shapes.
Answer:

The frictional force exerted by fluids is also called drag. When objects move through fluids, they have to overcome the friction acting on them. In this process, they lose their energy.

Efforts are made to minimise friction. So, objects are given special shapes, and this type of shape is known as a streamlined shape.