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Homework Help: Center of Mass/Momentum

  1. Nov 18, 2008 #1
    1. The problem statement, all variables and given/known data
    The question is: Romeo and Juliet are dating on a canoe in a lake. They are 4 feet apart, and Romeo wants to see how much Juliet weighs. He is on the left, Juliet on the right. So, he decides to switch spots with her. After switching, the boat moves 0.444 feet to the left. Romeo weighs 160 pounds. How much does Juliet weigh?

    2. Relevant equations

    Center of mass= sum (mgx) /sum (mg)

    3. The attempt at a solution
    Since the center of mass remains the same, the center of mass of the initial position is equal to the center of mass of the final position, minus 0.444 (since it moved to the left 0.444 feet). After solving for x ( weight of Juliet), I got 142 pounds..is this right? Please help..it sounds right, since Romeo weighs 160 pounds, and the boat moved to the left 0.444 feet (due to friction, and romeo is heavier...) thanks!!!
  2. jcsd
  3. Nov 18, 2008 #2
    bump...please? any help?
  4. Nov 18, 2008 #3
    Edit: I actually got 128 pounds, (little algebraic mistake). So, Juliet weights 128 pounds, is this correct..? Thanks!
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