A passenger bus in Zurich, Switzerland derived its motive power from the energy stored in a large flywheel. The wheel was brought up to speed periodically, when the bus stopped at a station, by an electric motor, which could then be attached to the electric power lines. The flywheel was a solid cylinder with a mass of 1010 kg and a diameter of 1.80 m; its top angular speed was 3080 rev/min.

Question

A passenger bus in Zurich, Switzerland derived its motive power from the energy stored in a large flywheel. The wheel was brought up to speed periodically, when the bus stopped at a station, by an electric motor, which could then be attached to the electric power lines. The flywheel was a solid cylinder with a mass of 1010 kg  and a diameter of 1.80 m; its top angular speed was 3080 rev/min.   
At this angular speed, what is the kinetic energy of the flywheel?

PART B 
If the average power required to operate the bus is 1.81×104 , how long could it operate between stops?

I am confused in this question.

For part A

I=mr^2/2 = (1010)(0.81)/2 = 409.05

For KE= 1/2 I w ^2
      = 1/2 (409.05)(19352.21075rev/min)
= 3958010.903

I think i did something wrong, can someone please direct me if i have.

drwls · Answer

1) The angular velocity w must be in rad/s, not rev/min. (Your number for w is actually rad/min.)

mumo · Answer

204

Tasnim · Answer

You have to look the equation of the solid cylinder I=1/2(m*r^2) and change the units of w to rad/s. After that, you can calculate and get the answer.