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 296-mile trip in a typical midsize car produces about 4.92 x 109 J of energy. How fast would a 18.9-kg flywheel with a radius of 0.445 m have to rotate to store this much energy? Give your answer in rev/min.

Explanation / Answer

KE = I w^2 / 2

and I = m r^2 /2

KE = m r^2 w^2 / 4

4.92 x 10^9 = (18.9) (0.445^2) w^2 / 4

w = 72514 rad/s

w = 72514 (1/2pi)rev / (1/60) min

w = 6.92 x 10^5 rev/min ......Ans

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