MCQ
Which of the following statements is not correct
  • A
    During pure rolling, the instantaneous speed of the point of contact is zero.
  • During pure rolling, the instantaneous acceleration of the point of contact is zero.
  • C
    For perfect rolling motion, work done against friction is zero.
  • D
    A wheel moving down a perfectly frictionless inclined plane will slip but not roll on the plane.

Answer

Correct option: B.
During pure rolling, the instantaneous acceleration of the point of contact is zero.
b
A rolling body can be imagined to be rotating about an axis passing through the point  of contact of the body with the ground. Hence, the instantaneous speed of the point  of contact is zero. 

Thus, statement $(a)$ is correct. 

As the body is rotating, its  instantaneous acceleration is not zero. 

Hence, statement $(b)$ is incorrect. 

Once  perfect the rolling begins, force of friction becomes zero. Hence, work done against  friction is zero. 

Thus, statement $(c)$ is correct. 

Rolling cannot take place in the  absence of friction because it is the frictional force that provides the necessary torque  which makes the body roll on a surface. When the inclined plane is perfectly  smooth, the wheel will simply slip under the effect of its weight. 

Hence, statement $(d)$  is correct. 

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