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# Work done with torque and angular momentum

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How much work is done by the motor in a CD player to make a CD spin, starting from rest? The CD has a diameter of 12.8 cm and a mass of 15.5 g. The laser scans at a constant tangential velocity of 1.16 m/s. If we assume that the music is first detected at a radius of 20.3 mm from the center of the disk. Ignore the small circular hole at the CD's center.

https://brainmass.com/physics/energy/work-done-torque-angular-momentum-210626

#### Solution Preview

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All the work done by the motor is converted into kinetic energy.

A kinetic energy of a rotating object is given by:

E = (1/2) * I * w^2

Where I is the moment of inertia ...

#### Solution Summary

This solution provides step by step calculations for determining work done with torque and angular momentum.

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