A CD has a playing time of 74 minutes. When the music starts the CD is rotating at angular speed of 480 revolutions per minute (rpm). At the end of the music, the CD is rotating at 210 rpm. Find the magnitude of the average angular acceleration of the CD. Express your answer in rad/s^2.

Angular acceleration equals change in rotational velocity divided by time:


\alpha = \frac {\Delta \omega} t

You'll have to convert the rotational speeds from RPM to radians per second and time from minutes to seconds, then do the math.