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Homework Help: Mastering physics :/

  1. Mar 7, 2005 #1
    Ok here is the problem A hollow spherical shell with mass 2.50kg rolls without slipping down a slope that makes an angle of 30.0 degrees with the horizontal.
    > Find the acceleration a_cm of the center of mass of the spherical shell.
    > Take the free-fall acceleration to be g=9.80m/s^2.
    > I got 24.2068 but again I was wrong

    - I though it was mgsin(theta) was it not?

    > Find the frictional force acting on the spherical shell.
    Im not sure but wouldnt it be coefficient of friction (which I do not know) times the normal force (which would be the answer to the above I think?)

    Another problem is :
    A circular hoop of mass m, radius r, and infinitesimal thickness rolls without slipping down a ramp inclined at an angle theta with the horizontal. View Figure
    > http://session.masteringphysics.com/problemAsset/1010918/22/MAD_ia_2_v1.jpg
    > What is the acceleration a of the center of the hoop?
    > Express the acceleration in terms of physical constants and all or some of the quantities m, r, and theta.

    and to be honest I have no clue whatsoever on how to do that problem :/ man Im beginning to hate physics I dont understand it at all
  2. jcsd
  3. Mar 7, 2005 #2
    Well, you know that the mass is 2.5 Kg, now find an equation to find I, the rotational inertia, given that all of the mass is in the spherical shell.
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