## Q1: Fill in the blanks:

(a) Friction opposes the ………. between the surfaces in contact with each other.

(b) Friction depends on the ………. of surfaces.

(c) Friction produces ………. .

(d) Sprinkling of powder on the carrom board ………. friction.

(e) Sliding friction is ………. than the static friction.

Ans.

(a) relative motion

(b) smoothness (or irregularities or nature)

(c) heat

(d) reduces

(e) smaller.

## (d) sliding, static, rolling

Ans. (c) static, sliding, rolling.

## (d) wet marble floor, dry marble floor, towel, newspaper.

Ans. (a) wet marble floor, dry marble floor, newspaper and towel.

## Q4: Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.

Ans. Frictional force will act upward i.e., direction opposite to that of sliding book.

## Q5: Explain why sportsmen use shoes with spikes.

Ans. It is done to provide the shoes better grip on the ground.

## Q6: Name the force responsible for wearing out of bicycle tyres.

Ans. Frictional force.

Ans.

(a) South

(b) North.

## Q8: What is the cause of friction?

Ans. The cause of friction is the irregularities on the two surfaces in contact.

## Q9: On which kind of surface the friction will be greater (i) smooth surface (ii) rough surface.

Ans. Friction will be greater in case of a rough surface.

## Q10: Does the use of ball bearing reduce or increase friction?

Ans. Use of ball bearing reduces the friction.

## Q11: Why do we sprinkle fine powder on the carrom board?

Ans. We want to reduce friction in order to increase efficiency.

## Q12: What are lubricants?

Ans. The substances which reduce friction are called lubricants.

## Q13: What is drag?

Ans. The frictional force exerted by fluids is also called drag.