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 450-mile trip in a typical midsize car produces about 4.20 x 109 J of energy. How fast would a 10.7-kg flywheel with a radius of 0.597 m have to rotate to store this much energy? Give your answer in rev/min.

Explanation / Answer

given,

energy = 4.2 * 10^9 J

mass = 10.7 kg

radius = 0.597 m

moment of inertia = 0.5 * m * r^2

moment of inertia = 0.5 * 10.7 * 0.597^2

by conservation of energy

initial energy = final energy

4.2 * 10^9 = 0.5 * 0.5 * 10.7 * 0.597^2 * w^2

w = 66372.5 rad/sec or 633810.68762201 rev/min

speed of flywheel = 633810.68762201 rev/min

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