A wheel is rotating at 900 rpm about its axis. When power is cut off it comes to rest in 1 min. The angular retardation in `rad s^(-2)` is

Options

A. `(pi)/(2)`
B. `(pi)/(4)`
C. `(pi)/(6)`
D. `(pi)/(8)`

Answer

A

Explanation

Angular velocity, `omega_(0)=(900xx2pi)/(60)"rad s"^(-1)=30 pi "rad s"^(-1)`
Now, `0=omega_(0)-alphat`
or Angular retardation, `alpha=(omega_(0))/(t)=(30pi)/(60)"rad s"^(-2) =(pi)/(2) "rad s"^(-2)`.