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Homework Help: Rotation Problem

  1. Nov 8, 2003 #1
    A disk witht the radius R is launched with the angular velocity ω on a horizontal surface. How long will it take until the disk stops, if the coefficient of friction is μ.

    This is what I came up with, but don't know if I did it correctly:

    For frictional force I got μMg
    -net torque = I(alpha), alpha = -μMg/.5MR = -2μg/R
    ω = ω0 +alpha(t) >> 0 = ω-(2μg/R)t

    I got t = (ωR)/(2μg) >>Is this the correct answer?

  2. jcsd
  3. Nov 8, 2003 #2
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