Home
Class 12
PHYSICS
To mop-clean a floor, a cleaning machine...

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 the floor is `mu`, the torque, applied by the machine on the mop is :

A

`2/3muFR`

B

`muFR//3`

C

`muFR//2`

D

`muFR//6`

Text Solution

Verified by Experts

The correct Answer is:
A
`dtau=(df).x=(muN)x`
`=mu(F)/(piR^(2)).2pixd.x`
`=(2muF)/(R^(2))x^(2)dx`
`tau=(2muF)/(3R^(2))R^(3)=(2muFR)/3`
Promotional Banner

Similar Questions

Explore conceptually related problems

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 mu the torque, applied by the machine on the mop is:

Find the ratio of magnetic dipole moment and magnetic field at the centre of a disc. Radius of disc is R and it is rotating at constant angular speed o about its axis. The disc is insulating and uniformly charged

A particle of mass M moves with constant speed along a circular path of radius r under the action of a force F. Its speed is

A thin circular disk of radius R is uniformly charged with density sigma gt 0 per unit area.The disk rotates about its axis with a uniform angular speed omega .The magnetic moment of the disk is :

A particle of mass 'm' moves with a constant speed along a circular path of radius r under the action of a force F .Its speed is given by

Motion of the rigid body is observed from an inertial frame of reference. Rigid body is rotating with constant angular speed about a fixed vertical axis. If we consider a particle of the rigid body not lying on its axis of rotation then net force acting on this particle is.

A circular wire of radius r rotates about its own axis with angular speed w in a magnetic field B perpendicular to its plane, then the induced e.m.f. is

A charge q is uniformly distributed on a non-conducting disc of radius R . It is rotated with an angular speed co about an axis passing through the centre of mass of the disc and perpendicular to its plane. Find the magnetic moment of the disc.

A hollow non conducting sphere of radius R has a positive charge q uniformly distributed on its surface. The sphere starts rotating with a constant angular velocity 'omega' about an axis passing through center of sphere, as shown in the figure. Then the net magnetic field at center of the sphere is