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 409-mile trip in a typical midsize car produces about 4.57 x 109 J of energy. How fast would a 47.6-kg flywheel with a radius of 0.260 m have to rotate to store this much energy? Give your answer in rev/min.

Explanation / Answer

Here

total energy , E = 4.57 *10^9 J

mass , m = 47.6 Kg

radius , r = 0.26 m

let the angular speed is w

Now , kinetic energy = 0.5 * I * w^2

E = 0.5 * 0.5 * m * r^2 * w^2

4.57 *10^9 = 0.25 * 47.6 * 0.26^2 * w^2

solving for w

w = 75373 rad/s

the angular speed of the wheel must be 75373 rad/s

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