Class 8th Science Chapter Friction

Class 8 Science - Chapter: Friction

1. Fill in the blanks:

• (a) Friction opposes the motion between the surfaces in contact with each other.
• (b) Friction depends on the nature of surfaces.
• (c) Friction produces heat.
• (d) Sprinkling of powder on the carrom board reduces friction.
• (e) Sliding friction is less than the static friction.

2. Four children were asked to arrange forces due to rolling, static, and sliding frictions in decreasing order. Choose the correct arrangement.

Answer: (c) static, sliding, rolling

3. Alida runs her toy car on different surfaces. The force of friction in increasing order will be:

Answer: (c) towel, newspaper, dry marble floor, wet marble floor

4. Suppose your writing desk is tilted a little. A book on it starts sliding down. Show the direction of the frictional force acting on it.

Frictional force acts in the opposite direction of motion. So, it will act upward along the slope, against the sliding book.

5. You spill a bucket of soapy water on a marble floor. Would it make it easier or more difficult to walk on the floor? Why?

It will make walking more difficult. Soapy water reduces friction between your feet and the floor, making it slippery and unsafe.

6. Explain why sportsmen use shoes with spikes.

Shoes with spikes increase friction with the ground. This helps sportsmen run faster and prevents them from slipping during the game.

7. Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who has to apply a larger force and why?

Seema has to apply more force because the heavier box presses more on the surface, increasing friction that resists motion.

8. Explain why sliding friction is less than static friction.

Sliding friction is less because once an object starts moving, the contact points don’t lock tightly, so less force is needed to keep it moving.

9. Give examples to show that friction is both a friend and a foe.

Friction as a Friend:

• Helps us walk safely without slipping.
• Helps us hold and grip objects firmly.
• Allows vehicles to stop when brakes are used.

Friction as a Foe:

• Causes wear and tear in machines and shoes.
• Wastes energy by producing heat in engines and moving parts.

10. Explain why objects moving in fluids must have special shapes.

Fluids like air and water resist motion. So, objects moving in them are given streamlined shapes to reduce drag and move easily.