A rigid and a disc of different masses are rotating with the same kinetic energy. If we apply a retarding torque `tau` on the ring, it stops after making n revolution. After how many revolutions will the disc stop, if the retarding torque on it is also `tau` ?

Options

A. n
B. 2n
C. 4n
D. n/2

Answer

A

Explanation

Workdone = Change in KE
`= tau theta`
= Constant
As `tau` is same in the two cases, `theta` must be same i.e. number of revolutions must be same.