A flywheel is a solid disk that rotates about an axis that is perpendicular to t

Question

A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk at its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible alternative to batteries in electric cars. The gasoline burned in a 300-mile trip in a typical midsize car produces about 1.20 109 J of energy. How fast would a 10-kg flywheel with a radius of 0.32 m have to rotate to store this much energy? Give your answer in rev/min.

Explanation / Answer

KE of a flywheel is (1/2) I w^2

where in this case I = (1/2) mr^2 = (1/2) * 10 * 0.32^2 = 0.512

So now...

1.20 x 10^9 = (1/2) * 0.512 * w^2

w = 68465.32 rad/sec = 653843.803 rev/min

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