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Circular motion of a cd

  1. Sep 26, 2008 #1
    A magnetic computer disk 8.0 cm in diameter is initially at rest. A small dot is painted on the edge of the disk. The disk accelerates at 600 rad/ s^2 for 1/2 s, then coasts at a steady angular velocity for another 1/2 s . a) What is the speed of the dot at t = 1.0 s?
    b)Through how many revolutions has it turned?

    for a) i kept getting the answer wrong:
    i did :
    so r=4.0 cm
    a=600 rad/s^2

    vi=(2)(pi)(4.0cm) / 1.0s

    so; vi=25m/s

    and for part b)
    i think you have to use the kinematic equation after you get vi.. i'm not sure tho.. am i right?? please help. thanks in advance!
  2. jcsd
  3. Sep 26, 2008 #2
    For part a) What is the velocity after .5s - v=a*t
    then coasts at a steady angular velocity for another .5 s - same Angular velocity as accelerated to
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