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Help needed to finding the mass

  1. Nov 29, 2009 #1
    urgent help needed to finding the mass

    1. The problem statement, all variables and given/known data
    We have a ruler with a total length L_r and a pivot at its middle. An object of known mass M_1 is placed a distance L_1 from the end of the ruler, as shown. An object of unknown mass M_2 is placed at the end of the ruler.

    http://session.masteringphysics.com/problemAsset/1010957/18/MFS_to_6_b.jpg

    Find the mass M_2.
    Express the mass in terms of M_1, L_1, and L_r.


    2. Relevant equations

    M_1*L_1 = M_2*L_2

    3. The attempt at a solution
    i tried doing ((M1)*0.5*(Lr)) / (L1 - 0.5Lr) but thats wrong and i dont understand why...
     
  2. jcsd
  3. Nov 29, 2009 #2
    Re: urgent help needed to finding the mass

    bump (please help!)
     
  4. Nov 29, 2009 #3
    Re: urgent help needed to finding the mass

    rebump
     
  5. Nov 30, 2009 #4

    ideasrule

    User Avatar
    Homework Helper

    Re: urgent help needed to finding the mass

    L_1 is L1-0.5Lr and L_2 is 0.5*Lr
     
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