Question

A fly wheel slows from 600 to 400rev/min while rotating through 40 revolutions.
A, what is the angular acceleration of the fly wheel?
B, how much time elapses during the 40 revolutions?

Answer 1

a)

$$\omega^2-\omega^2_0=2\alpha \theta\to 400^2-600^2=2(40)\alpha$$

$$\alpha=-2500\frac{rev}{min^2}$$

b)

$$400-600=-2500t$$

$$t=0.08\ min$$