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Homework Help: Torque required to slow down an object

  1. Nov 21, 2011 #1
    1. The problem statement, all variables and given/known data
    What is the angular momentum of a figure skater spinning (with arms in close to her body) at 3.32 revolutions per second, assuming her to be a uniform cylinder with a height of 1.41 m, a radius of 13.4 cm, and a mass of 50.4 kg.

    How much torque is required to slow her to a stop in 4.57 s, assuming she does not move her arms?

    2. Relevant equations

    I= (M x R^2) /2

    3. The attempt at a solution

    I got the first one, the angular momentum

    since I= (M x R^2) /2
    and w = 3.32*2∏

    L = Iw
    9.4 kg*m^2/s

    ang acc is total change in ang vel divided by total time for uniform angular acceleration

    α= w/4.57
    torque = Iα
    torque = 2.065N*m

    but its wrong

    anyone can help pls? thanks
    Last edited: Nov 21, 2011
  2. jcsd
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