A circular disc is rotating about its own axis at a uniform angular velocity `omega`. The disc is subjected to uniform angular retardation by which its angular velocity is decreased to `omega/2` during `120` rotations. The number of rotations further made by it before coming to rest is

Options

A. `120`
B. `60`
C. `40`
D. `20`

Answer

C

Explanation

`alpha` is constant `alpha=(omega_(1)^(2)-omega_(2)^(2))/(2 theta) , theta_(2)=(theta_(1))/3`