As you finish listening to your favorite compact disc (CD), the CD in the player

Question

As you finish listening to your favorite compact disc (CD), the CD in the player slows down to a stop. Assume that the CD spins down with a constant angular acceleration. If the CD rotates clockwise at 500 rpm (revolutions per minute) while the last song is playing, and then spins down to zero angular speed in 2.60 s with constant angular acceleration, what is , the magnitude of the angular acceleration of the CD, as it spins to a stop? Express your answer in radians per second.

B) How many revolutions does the CD make as it spins to a stop?

Explanation / Answer

from the rotational kinematic equation

= wf- wi/t

= 0- 500 rpm ( 2 pi/ 60)/ 2.60 s

=20.12 rad/s^2

(b)

theta = wf^2 - wi^2/2

= 0-(500 rpm ( 2 pi/ 60))^2/ 2( -20.12 rad/s^2)

= 68.06 rad( 1 rev/ 2pi rad)

=10.8 revolution

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