Question

A compact disc (CD), initially at rest, reaches an angular speed of 40 rad/s in 5.0 s.
a. What is the magnitude of its angular acceleration?
b. How many revolutions does the CD make in 5.0 s?

Answer 1

a. acceleration = speed / time ... 40 / 5.0

b. (average speed) * time
...[(0 + 40)/2] * 5.0

Answer 2

b. 40rad/s * 1rev/6.28rad * 5s = 31.85 rev.