NCERT Class 8 Science Chapter 9 Friction SAQs

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.