FRICTION

Friction is a ______________

• non-contact force

• contact force

• magnetic force

• electrostatic force

There are four objects resting on a wooden board. When pushed lightly, which object is most likely to roll off the board?

• Flat eraser

• Bent paper clip

• Round ball

• Wooden cube

The treaded tyres of cars, trucks and bus

• Increase the velocity of vehicles

• Increase the diameter

• Decrease friction of ground

• Provide better grip with ground and increase friction

  D

Fluid friction depends on

• The speed of the object

• Shape of the object

• The nature of the fluid

• All of these

Wrestlers rub their hands with sand to

• to increases friction

• to decrease friction

• to get strength

• to reduce the weight

The friction offered by fluids is called ______

• resistance

• force

• drag

• thrust

Two objects A and B are moving on a rough surface as shown in the figure. Object A has a greater velocity than B then

• A experiences more frictional force than B

• B experiences more frictional force than A

• Both experience same frictional force

• Cannot be said because data is insufficient.

In which of the following cases the friction is helpful (H) and troublesome (T)?

(a) Lighting a matchstick

(b) Applying the brakes on a cycle

(c) Use a towel to open the tightly closed lid of a bottle

(d) Pulling the drawer out of a desk

• (a) T (b) T (c) H (d) H

• (a) H (b) H (c) T (d) T

• (a) T (b) T (c) T (d) H

• (a) H (b) H (c) H (d) T

Use of ball bearing between the hubs is an example of rolling friction.

• True

• False

Friction produces __________