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Homework Help: Determine the magnitude of the angular acceleration of the discus

  1. Feb 14, 2005 #1
    A discus thrower accelerates a discus from rest to a speed of 25 m/s by whirling it though 1.25 rev. Assume the discus moves on the arc of a circle 1m in radius.

    Determine the magnitude of the angular acceleration of the discus:

    ω=angular velocity

    ω=v/r=25m/s / 1m = 25rad/s


    is this correct?
    Last edited: Feb 14, 2005
  2. jcsd
  3. Feb 14, 2005 #2


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    Science Advisor

    {Total Distance Moved} = d = (1.25 rev)*(2*Pi*r) = (1.25 rev)*{2*Pi*(1 m)} = 7.854 m
    {Acceleration} = (v^2)/(2*d) = {(25 m/sec)^2}/{2*(7.854 m)} = 39.79 m/sec^2
    {Angular Acceleration} = {Acceleration}/r = {39.79 m/sec^2}/(1 m)
    {Angular Acceleration} = 39.79 rad/sec^2

  4. Feb 14, 2005 #3

    Doc Al

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    Staff: Mentor

    Your method is correct but you plugged in 1.5 instead of 1.25. Correct that error and you'll get the answer that xanthym posted.
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