Question

A flywheel in a motor is spinning at 540.0 rpm when a power failure suddenly occurs. The flywheel has mass 40.0 kg and diameter 75.0 cm. The power is off for 36.0 s, and during this time the flywheel slows down uniformly due to friction in its axle bearings. During the time the power is off, the flywheel makes 230.0 complete revolutions.

1. At what rate is the flywheel spinning when the power comes back on?

2. How long after the beginning of the power failure would it have taken the flywheel to stop if the power had not come back on?

Express your answer in seconds.

3. How many revolutions would the wheel have made during this time?

Answer 1

Given:

Initial angular velocity of the flywheel,

To convert rpm to rad/s. Multiply by , then divide by 60.

Time duration of power failure,

Angular displacement,

To convert revolutions to rad. Multiply by

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1. At what rate is the flywheel spinning when the power comes back on?

Use formula

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Use formula

To convert rad/s to rpm. Multiply by 60, then divide by .

ANSWER:

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2. How long after the beginning of the power failure would it have taken the flywheel to stop if the power had not come back on?

If the power did not come, the flywheel will eventually stop.

Final angular velocity of the flywheel,

Use formula

ANSWER:

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3. How many revolutions would the wheel have made during this time?

Use formula

To convert rad to rev, Divide by

ANSWER:

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