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Homework Help: Yo-Yo Question - Rotational motion/angular momentum

  1. Feb 11, 2007 #1
    Moment of inertia center of mass....

    1. The problem statement, all variables and given/known data
    Assume: Friction is negligible.
    Given g= 9.81 m/s^2. The density of this large yo-yo like solid is uniform throughout. The yo-yo like solid has a mass of 2.8 kg. A cord is wrapped around the stem of the yo-yo like solid and attached to the ceiling. The radius of the stem is 5 m, and the radius of the disk is 6 m. Calculate the moment of inertia about the center of mass (axis of rotation). Answer in units of kg m^2.

    2. Relevant equations

    I = 1/2 M R^2

    3. The attempt at a solution

    I tried doing I = 1/2MR^2, which is wrong, I also thought of summing the I's of the two cylinders and the stem, but I that won't give you the I center of mass, and they don't give you the masses of the individual parts. I also tried MR^2 of the stem radius, also wrong. I also tried doing 1/2M(r^2 + R^2) which is also wrong. There are four parts to this question, but I think i can manage it as long as I get the inertia because I'm going to need it for the rest of the questions. Can anyone help me, I'm getting so frustrated with this problem!!
    Last edited: Feb 12, 2007
  2. jcsd
  3. Feb 12, 2007 #2
    Bump. Anyone?
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