Question

Which of the following statements is not correct?

• A. During rolling, the instantaneous speed of the point of contact is zero.
• B. During 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 1

Answer: (B)

During rolling, the instantaneous acceleration of the point of contact is zero.

Answer 2

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.

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

Hence, statement (2) is incorrect.

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

Thus, statement (3) is correct.

Rolling can not 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 (4) is correct.