Posted by **Mary** on Wednesday, March 14, 2007 at 1:48am.

A certain CD has a playing time of 80 minutes. When the music starts, the CD is rotating at an angular speed of 4.8 x 10^2 revolutions per minute (rpm). At the end of the music, the CD is rotating at 2.1 x 10^2 rpm. Find the magnitude of the average angular acceleration of the CD. Express your answer in rad/s2.

(0.104667 x -2.7) / (80 x 60)=

-0.000058875

[270 rev/min* 2 pi rad/rev* 1/60 min/sec]/(4800 sec) = 5.89*10^-3 rad/sec^2

You forgot the 10^2 multiplier on the rpms.

drwls the system is telling me the answer is incorrect. I saw where my I made the mistake and corrected it but it is still wrong. The answer I came up with is -0.00589 rad/sec^2.

You are right about the minus sign, since it is decelerating. Maybe they want you to use only two significant figures (-5.9*10^-3). Other than that, I don't see why it is getting marked wrong.

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