Question

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:

• 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 ration of the alternative masses of disc and plank.

Answer 1

Answer: (C)

The value of $F$ is zero.

No slipping implies that point A will not slip over the plank. Thus there is no friction force acting on the disc and plank.Hence force F is not needed to overcome any other force (as f= 0) so that the plank remains at rest.

$⟹F=0$