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Homework Help: Missing something

  1. Mar 11, 2005 #1
    A CD has a mass of 18.0 g and a radius of 6.11 cm. When inserted into a player, the CD starts from rest and accelerates to an angular velocity of 19.6 rad/s in 0.768 s. Assuming the CD is a uniform solid disk, determine the net torque acting on it.

    Formula im using: .5MR^2 for the I which = 25.5208
    Then the w= chg in radians/ chg in time
    Then the a = chg in w/ chg in time

    Net torque = Ia

    so i get 1827.33J which isnt right

    i also tried converting the g into kg and the cm into m but got wrong answer
  2. jcsd
  3. Mar 11, 2005 #2

    Doc Al

    User Avatar

    Staff: Mentor

    25.52 rad/sec^2 is the angular acceleration, not the rotational inertia.

    What did you calculate for I? (Yes, convert to standard units: kg & m)
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