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 |

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 |

1 Answer

127 votes

Consider a strip of radius x thickness dx,

Torque due to friction on this strip.

=

.

correct answer is (a)

127 votes

127