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 404-mile trip in a typical midsize car produces about 3.88 x 109 J of energy. How fast would a 21.9-kg flywheel with a radius of 0.227 m have to rotate to store this much energy? Give your answer in rev/min.

Explanation / Answer

KErot = I2/2 = mr22/4 = 3.88 * 109 J

=> = [3.88 * 109 * 4 / (21.9 * 0.2272)]1/2 = 11.73 * 104 rad/s = [11.73 * 104 * 60 / 2] rev/min = 1.12 * 106 rev/min

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