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The spin dryer of a washing machine rotating at 15 r.p.s. slows down to 5 r.p.s. after making 50 revolutions. Find its angular acceleration.

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#### Solution

Given:

n_{1} = 15 r.p.s

n_{2} = 5 r.p.s

No. of revolution = 50

As, ω = 2πn

ω = 2π x 5 = 10π

Also, ω_{0 }= 2πn_{0 }= 2π x 15 = 30π

Angular displacement in/revolution = 2π

Angular displacement in 50 revolution = 2 x 50π

= 100π

Now, `ω^2 = ω_0^2 + 2alphatheta`

`(10pi)^2 = (30pi)^2 + 2alpha(100pi)`

`900pi^2 - 100pi^2`

`= -alpha` =____________________________

`200pi`

`alpha = -4pi rad//s^2`

Also, `alpha = -12.56 rad//s^2`

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