Friction Worksheet-5

Friction Worksheet-5

1. John carried out an experiment to find out how different surfaces (P, Q, R and S) effect the distance a car travelling at 50 km/h needed to stop once the brakes are applied. The results are shown below:

Which type of road will provide the most friction for the car to stop?

(a) P                    (b) Q                   (c) R                    (d) S

2. Frictional force exists in which of the following cases?

(a) Exists only for moving bodies

(b) Exists only for bodies which are at rest

(c) Exists for both moving and non-moving bodies

(d) None of these

3. A person is moving on a rough horizontal surface towards east. Then the direction of friction forces is towards

(a) West             (b) East              (c) North            (d) South

4. When the applied force is doubled and the object is still at rest, then friction becomes

(a) Doubled                                   (b) Halved

(c) Quadrupled                             (d) Zero

5. It is difficult to move a cycle with brakes on because

(a) Rolling friction opposes motion on road

(b) Sliding friction opposes motion on road

(c) Rolling friction is more than sliding friction

(d) Sliding friction is more than rolling friction.

6. It is easier to pull a lawn roller than to push it because pulling

(a) Involves sliding friction

(b) Involves rolling friction

(c) Increases the effective weight

(d) Decreases normal reaction

7. To avoid slipping while walking on ice, one should take smaller steps because

(a) Frictional force of ice is large

(b) Of larger normal reaction

(c) Frictional force of ice is small

(d) Of smaller normal reaction.

8. Why does a horse need to pull harder during the first few steps in pulling the cart?

(a) Static friction is greater than sliding friction

(b) Sliding friction is greater than rolling friction

(c) No frictional force acts after the cart comes in motion

(d) Air friction is greater during first few steps of motion

9. Smoother the surface,

(a) Lesser is the friction it exerts on a given body in contact

(b) More is the friction it exerts on a given body in contact

(c) Sometimes less and sometimes more force depending on area of the body in contact

(d) All of these

10. Select the incorrect statement?

(a) Friction always acts in direction of motion of the surface

(b) Irregularities between two surfaces interlock to produce friction

(c) Soapy floor is slippery due to increased friction

(d) Friction is a necessary evil.

Answer Key:

(1)-(b); (2)-(c); (3)-(a); (4)-(a); (5)-(b); (6)-(b); (7)-(c); (8)-(a); (9)-(a); (10)-(c)