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Average Angular Acceleration of a CD

  • Thread starter kmb11132
  • Start date
  • #1
13
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Homework Statement



A CD has a playing time of 59.8 minutes. When the music starts, the CD is rotating at an angular speed of 460 revolutions per minute (rpm). At the end of the music, the CD is rotating at 202 rpm. Find the magnitude of the average angular acceleration of the CD. Express your answer in rad/s^2.

Homework Equations



angular acceleration = change in angular velocity / change in time

The Attempt at a Solution



initial angular velocity in rad/s:
460rpm / 60 * 2 * Pi = 48.17rad/s

final angular velocity in rad/s:
202rpm / 60 * 2 * Pi = 21.15rad/s

time in s:
59.8min * 60 = 3588s

angular acceleration:
(21.15 - 48.17) / 3588 = -.00753rad/s^2

I'm really not sure why this is incorrect. I feel like I'm making a really obvious/face-palm type mistake.
 

Answers and Replies

  • #2
Redbelly98
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I agree with your answer.

It sounds like you are submitting this for online grading. For some reason these are known to have bugs in terms of accepting answers that are slightly off or in a different format from what the accepted answer is. I am always puzzled as to why they can't get it to act right.
 
  • #3
13
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You're exactly right. I'm using the WileyPlus system and it expected scientific notation without explicitly stating so.
 

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