When a body is sliding over other body with a constant speed, the force of friction acting on it is
Static friction.
Limiting friction.
Dynamic friction.
Rolling friction.
Which of the following statements is correct about frictional force?
It exists only for moving bodies.
It exists only for bodies which are at rest
It exists for both moving and non-moving bodies
None of these
Which of the following material is likely to have least friction?
Wood.
Plastic.
Glass.
Paper.
Friction reduces efficiency of machines due to
Production of heat.
Wearing out of moving parts.
Increase in energy consumption.
All of the above.
Which of the following describe a frictional force?
I. Frictional force always opposes the motion of an object
II. Frictional force is parallel to the surface in contact.
III. Frictional force always produces heat.
IV. Frictional force can be increased or reduced.
I and II only
III and IV only
I, II and III only
I, II and IV only
How does the proper inflation of tyre save fuel?
Normal reaction decreases
Normal reaction increases
Sliding contact with the road decreases
Sliding contact with the road increases
It is easier to pull a lawn roller than to push it because pulling
Involves sliding friction
Increases the effective weight
Involves rolling friction
Decreases normal reaction
In which of the following cases more friction is desirable?
Movement of piston in a cylinder.
Braking of a vehicle.
Running on a track.
Which of the following statement is CORRECT?
Rolling a body is easier than sliding.
Sliding body is easier than rolling.
Dragging body is easier than sliding.
Dragging body is easier than rolling.
