# 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 disturbed uniformly over the mop and if coefficient of friction between the mop and the floor is the torque applied by the machine on the mop is : (a) FR (b) FR/3 (c) FR/2 (d) FR/6

## Question ID - 50226 :- 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 disturbed uniformly over the mop and if coefficient of friction between the mop and the floor is the torque applied by the machine on the mop is : (a) FR (b) FR/3 (c) FR/2 (d) FR/6

3537

Answer Key : (a) -

Consider a strip of radius x  thickness dx,

Torque due to friction on this strip.

=

.

correct answer is (a)

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