The spin drier of a washing machine revolving at 15 r.p.s slows down to 5 r.p.s., while making 50 revolutions. Find (a) angular acceleration and (b) time taken.

Explanation

Here `omega_(0)=15 r.p.s =30 pi rad s^(-1)`
`omega_(0)=5r.p.s =10 rad s^(-1), theta=50xx2pi =100 pi` rad
(a) Now `omega^(2)-omega_(0)^(2)=2 alpha theta`
`:.(10pi)^(2)-(30 pi)=2 alpha xx100 pi or alpha=-4 pi rad s^(-2)`
(b) Also `omega=omega_(0)+ alpha t`
`:.10 pi =30 pi +(-4pi)xx t or t=5s`