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Homework Help: A little help , rotational and youngs modulus

  1. Nov 21, 2008 #1
    A little help plz, rotational and youngs modulus

    1. The problem statement, all variables and given/known data
    A solid Ball with a mass of 3kg and r=1m is suspended in the center of a hollow ball of mass=1kg and r=3m. It is placed at rest on a 33 degree incline. after rolling 1km along the incline whats the final tangetial velocity? whats the objects final angular momentum?

    2. Relevant equations
    I know i need I=mr^2
    and Im pretty sure this is a conservative problem so KEi+PEi=KEf+PEf
    KE=Iw^2 and KE=1/2mv^2
    PE=mgh or mgr

    3. The attempt at a solution
    Im not too sure how to input the problem at all...should I combine the two moments of Inertia? then go from there or should they both be done seperately? This problem is killing me

    thanks in advance everyone
  2. jcsd
  3. Nov 21, 2008 #2


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    Hi invisiblewar! :smile:

    (have an omega: ω :wink:)
    Yes, moments of inertia (about the same axis) are scalars, so you just add them. :smile:

    (and it's rolling, so don't forget to find the equation relating v to ω :wink:)
  4. Nov 21, 2008 #3
    Re: A little help plz, rotational and youngs modulus

    awesome thanks so much
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