Question 12

The operation of the Princeton TFTR (Tokomak Fusion Test Reactor) requires very large amounts of energy that have to be supplied in "pulses", i.e. in a short time. The needed power, namely hundreds of kilowatts during a pulse, cannot be delivered by the nearby power plants. Therefore, prior to pulsing the reactor, energy is stored in a giant 800 ton flywheel which is rotating at 386 rpm when it is at its maximum speed. When this stored energy is needed, the wheel (which is part of an electrical generator) is slowed down and the mechanical energy converted to electrical energy.

The moment of inertia of the flywheel is 5.0*10⁶ kg*m². If the wheel is initially running at 350 rpm and is then slowed down to 250 rpm in 5.0 seconds, the average power supplied by the device during that time is, in megawatts (1 megawatt = 10⁶ W):

• A.    8.3 MW
• B.    670 MW
• C.    1640 MW
• D.    330 MW
• E.    1.2*10⁶ MW
• F.    Not withing 10% of any of the above

Formula Sheet

Question 11

Question 13

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