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Homework Help: Average Angular Acceleration

  1. Nov 7, 2011 #1
    A CD has a playing time of 74.2 minutes. When the music starts, the CD is rotating at an angular speed of 488 revolutions per minute (rpm). At the end of the music, the CD is rotating at 215 rpm. Find the magnitude of the average angular acceleration of the CD. Express your answer in rad/s^2.

    t = 74.2 min or 4344 sec
    w0 = 488 rev/min * 2pi rad = 3066 rad/min / 60 sec/min = 51 rad/sec
    w = 215 rev/min * 2pi rad = 1350 rad/min / 60 sec/min = 23 rad/sec

    av ang acc = w - w0 / t = (23 - 51) / 4344 = -.0064 rad/sec^2

    WileyPlus tells me my answer is wrong. Tried a positive answer, too.
    I'm stumped!


    Wiley needed more significant figures
    Last edited: Nov 7, 2011
  2. jcsd
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