ssm A flywheel is a solid disk that rotates about an axis that isperpendicular t

Question

ssmA flywheel is a solid disk that rotates about an axis that isperpendicular to the disk at its center. Rotating flywheels providea means for storing energy in the form of rotational kinetic energyand are being considered as a possible alternative to batteries inelectric cars. The gasoline burned in a 390 mile trip in a typical midsize car produces about1.20 x109 J ofenergy. How fast would a 17 kg flywheelwith a radius of 0.27 m have to rotate inorder to store this much energy? Give your answer in rev/min.
Enter anumber. 1 rev/min
Enter anumber.

Explanation / Answer

We know that kinetic energy    KE = 1/2 I2          = 1/2 [ 1/2mr2 ] 2 1.2*109 J = 1/4 m r2 2 1.2*109 J = 1/4 (17kg) (0.27m)2 2 therefore    = [ ( 1.2*109 ) / (1/4* (17kg) (0.27m)2   ]        = 3.87*103 rad/s in terms of rev/ min     = 36.97 rev/ min

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