physics
posted by Chan on .
hi,need help please.thank.
A car is designed to get its energy from a rotating flywheel (solid disk) with a radius of 2.00 m and a mass of 525 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.
1 J
(b) If the flywheel is to supply energy to the car as would a 20.0hp motor, find the length of time the car could run before the flywheel would have to be brought back up to speed.
2 h

Are those your answers? 1 J and 2 h? How dd you obtain them?
a) Use the formula E = (1/2) I w^2, where w is the angular speed in rad/s and I is the moment of inertia.
(b) Time = (Full speed energy)/Power
You will have to convert horsepower to Watts when using the formula.