Question

Read each statement below carefully, and state, with reasons, if it is true or false;

(a) During rolling, the force of friction acts in the same direction as the direction of motion of the CM 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. Question 7.32 System Of Particles And Rotational Motion

Answer 1

(A) True , because during rolling motion , the direction of the motion of the point of contact of the rolling body with the surface is in opposite direction of the motion of COM hence, friction { which opposes the relative motion} act in the direction of motion of the centre of mass .
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(B)True , the instantaneous speed of the point of contact during rolling is zero, because during perfectly rolling , the body can be imagined to be rotating about an axis passing through point of contact of the body with the surface so, instantaneous speed of it is zero.
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(C)false, motion is rotational , in which acceleration isn't zero.
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(D) True , we know,in perfect rolling motion , force of friction becomes zero. Hence, work done against force of friction becomes zero.
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(E) True , becoz rolling takes place by the torque provided by the tangential friction force. On a perfectly frictionless inclined plane , force of friction is zero so, body will slip without friction.