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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 443-mile trip in a typical midsize car produces about 2.67 x 10^9 J of energy. How fast would a 38.3-kg flywheel with a radius of 0.363 m have to rotate to store this much energy? Give your answer in rev/min.

Respuesta :

Answer:

The angular velocity is [tex]2.64\times 10^{5}\ rev/min[/tex]

Solution:

As per the question:

Energy produced by gasoline, E = [tex]2.67\times 10^{9}[/tex]

Mass of the flywheel, m = [tex]38.3\ kg[/tex]

Radius of the flywheel, R = 0.363 m

Now,

The moment of Inertia of the disc is given by:

[tex]I = \frac{1}{2}mR^{2}[/tex]

[tex]I = \frac{1}{2}\times 38.3\times 0.363^{2} = 6.95\ kg-m^{2}[/tex]

Now, the angular velocity can be calculated as:

[tex]E = \frac{1}{2}I\omega ^{2}[/tex]

[tex]\omega = \sqrt{\frac{2E}{I}}[/tex]

[tex]\omega = \sqrt{\frac{2\times 2.67\times 10^{9}}{6.95}} = 27719\ rad/s[/tex]

Now,

1 revolution = [tex]2\pi\ rad[/tex]

Now,

[tex]\omega = \frac{27719\times 60}{2\pi} = 2.64\times 10^{5}\ rev/min[/tex]