question_answer

To mop-clean a floor, a cleaning machine presses a circular mop of radius R vertically down with a total force F and rotates it with a constant angular speed about its axis. If the force F is distributed uniformly over the mop and if coefficient of friction between the mop and the floor is u, the torque, applied by the machine on the mop is - [JEE Main 10-Jan-2019 Morning]

A)   \[\mu \,FR/2\]              

B)        \[\mu \,FR/3\]

C)   \[\mu \,FR/6\]         

D)        \[\frac{2}{3}\mu \,FR\]

Correct Answer: D

Solution :

[d]

Text will counter balance the torque by friction