Rotational motion of a high speed flywheel.

[graustet]

Homework Statement

A high-speed flywheel in a motor is spinning at 450 rpm when a power failure suddenly occurs. The flywheel has mass 36.0 kg and diameter 70.0 cm. The power is off for 34.0 s and during this time the flywheel slows due to friction in its axle bearings. During the time the power is off, the flywheel makes 180 complete revolutions.

At what rate is the flywheel spinning when the power comes back on?

Homework Equations

This is where i need help! i don't know how to set up the problem so that i can find the answer.

The Attempt at a Solution

 

[berksted]

I think you should make a wild attempt at a solution first even if you are not sure. Think about what is happening to the fly wheel at the end of the 34 seconds when the power is off.