Question

In the spin cycle of a clothes washer, the drum turns at 635 rev/min. If the lid of the washer is opened, the motor is turned off. If the drum requires 8.0 s to slow to stop, what is the angular acceleration of the drum?

Answer 1

(-635rev/min)/(8s) = -79.375 rev/min/s
you can convert that to rev/min^2 or rev/s^2
you didn't say what you wanted.

Answer 2

and then 1 rev = 2 pi radians so you can get radians/s^2 which is the most common unit of angular acceleration.