1. The problem statement, all variables and given/known data A car is designed to get its energy from a rotating flywheel (solid disk) with a radius of 1.00 m and a mass of 425 kg. Before a trip, the flywheel is attached to an electric motor, which brings the flywheel's rotational speed up to 4000 rev/min. (a) Find the kinetic energy stored in the flywheel. (b) If the flywheel is to supply energy to the car as would a 15.0-hp motor, find the length of time the car could run before the flywheel would have to be brought back up to speed. 2. Relevant equations KE=(1/2)Iw^2 where I=Mr^2 P=KE/t 3. The attempt at a solution First I used the equation to find the moment of inertia: I=(425kg)(1)^2=425 I know that the angular velocity is 4000 rev/min, so I converted that to 418.879 rad/s Then I plugged that into the the equation for KE: 1/2(425)(418.879 rad/s)^2 =3.73e7 This was wrong... For part b, I used the equation relating power to kinetic energy, so I converted 15 hp to 11185.5 Watt So, 3.73e7/11185.5 = t = 3334.67s Also wrong.. Is there something I'm missing here? I can't figure out for the life of me what I'm doing wrong.