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Homework Help: Angular Acceleration. Im totally lost

  1. Oct 18, 2008 #1
    1. The problem statement, all variables and given/known data
    A computer disk is turned on starting from rest and has constant anglular acceleration. If it took 0.570s for the drive to make its second complete revolution, how long did it take to make the first complete revolution? Also what is its angular acceleration

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 18, 2008 #2


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    Welcome to Physics Forums.

    The homework template is there for a reason, please use it. You are expected to show some effort in solving the problem yourself when asking for help.
  4. Oct 18, 2008 #3
    Well I know the inital velocity is zero (starting from rest) and the time is given. Converting 2 revs to rads is 12.57. So it completes 12.57 rads in 0.570s. Im also aware that ang accel = ang vel/time. Im just going around in circles trying to work it out. I was fairly sure it was wrong to assume speed is 22rad/s. (12.57/.570). Sorry if thats not enough but im totally lost. First post so I wasnt sure what to put up
  5. Oct 20, 2008 #4


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    Angular calculations are pretty much the same as linear. Recall then that:

    x = 1/2*a*t2

    In your case use x as radians and solve for a.

    Armed with a (which is your angular acceleration by the way) solve for t at half the distance - which is one revolution.
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