Physics
posted by TP .
A wheel turns through 90.0 revolutions in 15.0 sec. The angular speed at the end of this 15.0 sec period is 10.0 rev/s. Assuming that the angular acceleration is constant, calculate a) the angular speed at the beginning of the 15.0 sec interval, and b) the amount of time that elapsed from when the wheel was at rest and the beginning of the 15.0 sec interval.

avg angular speed=90rev/15sec=6 rev/sec
but avg ang speed=(wf+wi)/2
or 6=(10+wi)/2 so wi= 2 rpm
b. If it took 15 sec to increase by 8 rpm, it took 15*2/8= sec to get to 2rpm.