A bus is designed to draw its power from a rotatingflywheel that is brought up t

Question

A bus is designed to draw its power from a rotatingflywheel that is brought up to its maximum speed of 3820 rpmby an electric motor. The flywheel is a solid cylinderof mass 453 kg and diameter 1.57 m. If the bus requiresan average power of 9.26 kW, how long does the flywheel rotateif all of the energy of the flywheel is used bythe bus? Answer in units of s. A bus is designed to draw its power from a rotatingflywheel that is brought up to its maximum speed of 3820 rpmby an electric motor. The flywheel is a solid cylinderof mass 453 kg and diameter 1.57 m. If the bus requiresan average power of 9.26 kW, how long does the flywheel rotateif all of the energy of the flywheel is used bythe bus? Answer in units of s.

Explanation / Answer

mass m = 453 kg diameter d = 1.57 m radius R = d / 2 = 0.785 m Moment of inertia I = ( 2/ 5 ) M R ^ 2 Average power P = 9.26 kW = 9260 W work done W = change in rotational kinetic energy                       = ( 1/ 2) I [ w ' ^ 2 - w ^ 2 ] where w ' = final angular speed = 3820 rev / min                = 3820 * 2 rad / 60 s                = 400 rad / s            w= initial angular speed = 0 rad / s substitue values we get work W value we know power P = W / t from this required time t = W / P substitue values we get answer

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