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 126-mile trip in a typical midsize car produces about 2.99 x 109 J of energy. How fast would a 45.8-kg flywheel with a radius of 0.512 m have to rotate to store this much energy? Give your answer in rev/min.

Answer 1

ω = ?

mass = 45.8kg

r = 0.512m

E = 2.99*10⁹J

Kinetic Energy of rotation = I * ω²

K.E = I * ω²

I = ½ m*r²

I = ½ * 45.8 * (0.512)²

I = 6.0kgm²

K.E = ½ * I * ω²

ω = √(2K.E / I )

ω = √[( 2* 2.99*10⁹) / 6]

ω = 3.157*10⁴ rad/s