A cylinder executes pure rolling without slipping with a constant velocity on a plank, whose upper surface is rough enough, but lower surface is smooth. The plank is kept at rest on a smooth horizontal surface by the application of an external force `F`. Choose the correct alternative:

Options

A. The direction of `F` is towards right.
B. The direction of `F` towards left.
C. The value of `F` is zero
D. The direction of `F` depends on the ratio of the relative masses of disc and plank.

Answer

C

Explanation

Since cylinder rolls with a constant velocity so there is no friction between the upper surface of the plank and the cylinder. The plank is at rest, unjder the influence of the weight of the cylinder. So no external force is required to keep the plank in equilibrium.