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 2.11 x 109 J of energy. How fast would a 16.8-kg flywheel with a radius of 0.496 m have to rotate to store this much energy? Give your answer in rev/min.

Explanation / Answer

moment of inertia of flywheel, I = 0.5*mr^2 = 0.5*16.8*0.496^2= 2.07 kg.m2

energy stored , E = 0.5*I*W^2

where W =angular speed

So, 2.11*10^9 = 0.5*2.07*W^2

So, W = 4.52*10^4 rad/s = 4.52*10^4*60/(2*pi) = 4.31*10^5 rev/min

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