Read each statement below carefully and state with reasons, if it is true ot false. (a) During rolling the force of friction acts in the same direction as the direction of motion of c.m of the body. (b) The instantaneous speed of the point of contact during rolling is zero. (c ) The instantaneous acceleration of the point of contact during rolling is zero. (d) For perfect rolling motion, work done against friction is zero. (e) A wheel moving down a perfectly frictionless inclined plane will undergo slipping (not rolling motion).

Explanation

(a) False, the force of friction acts in the opposite direction as the direction of motion of the CM of the body.
(b) True, as a rolling body is imagined to be rotating about an axis passing through the point of contact of body with the ground. Hence, the instantaneous speed of the point of contact during rolling is zero.
(c) False, because as the body is rotating, the instantaneous acceleration is not zero.
(d) True, as the perfect rolling begins, force of friction becomes zero. So work done against force of friction also becomes zero.
(e) True, when the inclined plane is perfectly smooth, there will be no frictional force, so rolling is not possible in the absence of frictional force and the wheel will only slip under the effect of its own weight.