Question

The figure shows a spool placed at rest on a horizontal rough surface. A tightly would string on the inner cylinder is pulled horizontally with a force F. Identity the correct alternative related to the friction force $f$ acting on the spool

• A. f acts leftwards
• B. $f$ acts leftwards but nothing can be said about its magnitude
• C. $f<F$ but nothing can be said about its magnitude
• D. None of the above

Answer 1

The correct option is C $f<F$ but nothing can be said about its magnitude

Torque of $F$ about $P$ is clockwise. So, spool will move towards right. Torque of motion will provide the clockwise torque about centre.
So$f$ is leftwards. Further, a is towards right, so, $F>f$