# Angular acceleration

posted by
**Jim (BIGEYE)**
.

A flywheel of 480 mm diameter is accelerated with an angular velocity of 0.4 rad/s^-2 from rest by an electric motor until it is rotating at 400 revs/minute. Calculate:

a) the time of acceleration

b) the linear speed of the rim of the flywheel

My answer for (a) is 104.7 secs, and for (b) is 10 m/s.

Appreciate if someone could check these answers if correct. If wrong, can they point me in the right direction.

TIA

Final angular speed = (angular acceleration) * time

400 rpm = 41.89 rad/s = (ang. acc.) * t

t = 104.7 s

final linear speed = R * (final angular speed) = [(0.48 m)/2]*41.89 rad/s = 10.05 m/s, but it is OK to show two significant figures, (10 m/s)

Thanks for that.