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 162-mile trip in a typical midsize car produces about 4.12 x 10⁹ J of energy. How fast would a 41.4-kg flywheel with a radius of 0.229 m have to rotate to store this much energy? Give your answer in rev/min.

Answer 1

Given that:

Mass of the flywheel (disc), m = 41.4 kg

Radius of the flywheel, r = 0.229 m

Hence, moment of inertia of the flywheel (solid disc) will be:

Given that, total energy, K = 4.12 x 10⁹ J

We know that, rotational kinetic energy is given by:

Therefore, Angular speed is given by:

Now we need to convert this into rev/min:

------------- (**Answer**)

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