A wheel is rotating at 1800 rpm about its own axis. When the power is switched off, it comes to rest in 2 min. Then, the angular retardation in `rad s^(-1)` is

Options

A. `2pi`
B. `pi`
C. `pi //2`
D. `pi//4`

Answer

C

Explanation

First equation of rational mtion
`omega = omega _(0) = alpha t `
whre `omega 2 pi n = 2pi xx ( 1800)/(60)`
`= 60 pi` rps
`omega _(0) =0`
`t = 2 xx 60 = 120 s`
`60 pi = 0 + alpha xx 120 s `
`alpha = ( 60 pi)/(120)`
` alpha = (pi)/(2) rad//s ^(2)`