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 260-mile trip in a typical midsize car produces about 1.77 x 109 J of energy. How fast would a 40.2-kg flywheel with a radius of 0.579 m have to rotate to store this much energy? Give your answer in rev/min.

Explanation / Answer

Given that

energy E=1.77*10^9 J

mass m=40.5 kg

radius r=0.579 m

basing on the concept of rotational motion

now we find the angular velocity

k.E=1/2Iw^2

=1/2*1/2mr^2*w^2

1.77*10^9=1/4*40.2*0.579^2*w^2

w^2=5.3*10^8

angular velocity W=(5.3*10^8)^1/2=2.3022*10^4=23022 rad/sec

=219843.91 rev/min

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