A wheel rotating at a speed of 120 rpm about its axis is brought to rest by applying a constant torque for `4 s`. Find the number of revolutions completed by the wheel before stop.

Explanation

Initial angular velocity
`omega_(0)=2piN=(2pixx120)/(60)=4pi rad//s`
`omega=omega_(0)-alpha t`
`0=4pi-alphaxx4 implies alpha=pi rad//s^(2)` (angular deceleration)
`theta=omega_(0)t-(1)/(2)alpha t^(2)=4pixx4-(1)/(2)pi(4)^(2)=8pi rad`
Number of revolutions `N= (theta)/(2pi)=(8pi)/(2pi)=4`