Science
posted by John .
At t = 0 s a flywheel is rotating at 30 rpm. A motor gives it a constant acceleration of 0.9 rad/s^2 until it reaches 70 rpm. The motor is then disconnected. How many revolutions are completed at t = 20 s?

Vo=30rev/min * 1min/60s * 6.28rad/1rev = 3.14rad/s.
d = Vo*t + 0.5a*t^2,
d = 3.14*20 + 0.45*(20)^2 = 242.8rad.
Rev = 242.8rad / 6.28rad/rev = 38.7.