At t=0 a grinding wheel has an angular velocity of 21.0 rad/s . It has a constant angular acceleration of 30.0 rad/s2 un

[answerhappygod]

At t=0 a grinding wheel has an angular velocity of 21.0 rad/s .
It has a constant angular acceleration of 30.0 rad/s2 until a
circuit breaker trips at time t = 2.20 s . From then on, it turns
through an angle 440 rad as it coasts to a stop at constant angular
acceleration. Part B question: At what time did it stop? (Part A:
Through what total angle did the wheel turn between t=0 and the
time it stopped? Answer: 559 rad). Part B answer: 12.3 seconds. I
just don't know how to get there.