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 333-mile trip in a typical midsize car produces about 2.98 x 109 J of energy. How fast would a 27.0-kg flywheel with a radius of 0.565 m have to rotate to store this much energy? Give your answer in rev/min.

Explanation / Answer

We know that the rotational kinetic energy = (1/2)IW2  where I is the moment of inertia , W is the angular velocity.
Moment of inertia of disc about the axis perpendicualr to the centre = (1/2)mr2 where m is the mass of the flywheel and r is the radius of the disc.
I = (1/2)(27)(0.565)2 = 4.309 kg-m2
Energy = (1/2)IW2 = 2.98*109
W = 37190 rad/s
We know that W= (2Pi*N)/60
N= 355145 .458 rpm

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