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Homework Help: Position of Center Mass Question

  1. Apr 1, 2009 #1
    1. The problem statement, all variables and given/known data

    Romeo (80.0 kg) entertains Juliet (58.0 kg) by playing his guitar from the rear of their boat at rest in still water, 2.80 m away from Juliet, who is in the front of the boat. After the serenade, Juliet carefully moves to the rear of the boat (away from shore) to plant a kiss on Romeo's cheek. How far does the 85.0 kg boat move toward the shore it is facing?

    ___________ m

    2. Relevant equations

    x_cm = (m1*x1 + m2*x2 + ... ) / (m1 + m2 + ... )

    3. The attempt at a solution

    Im kind of confused on this problem and really need help..

    So far I was trying to figure it out but i think i went the wrong way.. My thinking was that there was no external force on the system, so we could just set two equtions equal to eachother.

    In doing so i came out with..

    Initially, x_cm = [(m_B * L/2) + (m_J * L)] / (m_R + m_B + m_J)


    Now, x_cm = [ m_B*(d + L/2) + d*(m_R * m_J) ] / [m_R + m_B + m_J]

    After setting those equal and solving for d, i came out with .03437m which was the wrong answer..

    Can anyone please help me and lead me in the right direction???
  2. jcsd
  3. Apr 1, 2009 #2
    nevermind, i somehow got it, not sure i completely understand it, but i will in time =]
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