Physics Rotaional Kinetic Energy
posted by Anonymous on .
A car is designed to get its energy from a rotating flywheel with a radius of 1.50 m and a mass of 600 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.

Model the flywheel as a sold disk, look up the moment of inertial
KE= 1/2 I w^2 where w=4000^2PI/60 rad/sec
change 15hp to kwatts
time= power/KEabove 
Can i have more help i tried that every time in part a and get the wrong answer on my webassign i tried it 5 times and got five different answers. the answer would be nice so i can get part b.