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Homework Help: Center of mass with one object moving

  1. Apr 2, 2012 #1
    1. The problem statement, all variables and given/known data

    Two objects are on a stick where one is stuck in place and the other one can slide. Both objects have the same mass and the stick has negligible mass.

    2. Relevant equations

    [tex] COM = \frac{m_1 x_1 + m_2x_2}{m_1+m_2}[/tex]
    [tex] v_1 = t [/tex]

    3. The attempt at a solution

    [tex] COM = \frac{m_1 \int v_1 + m_2x_2}{m_1+m_2}[/tex]

    Would this be correct assuming that the starting point for measuring x1 and x2 would be the left side? Thanks

    Attached Files:

    • COM.jpg
      File size:
      3.9 KB
  2. jcsd
  3. Apr 2, 2012 #2
    I would be a little careful here. You need to know the initial position of the moving mass:
    [tex]\frac{m_1\left (\int v_1(t) \,dt +x_1(0) \right ) + m_2x_2}{m_1+m_2}[/tex]
    where x_1(t) is a function of time and x_1(0) is the constant of integration.
    Last edited: Apr 2, 2012
  4. Apr 2, 2012 #3
    Thanks for responding. Ahh yes good point. Adding your part, would that be correct? I just made up the problem which is why I'm a little unsure of the conceptual part.
  5. Apr 2, 2012 #4
    I believe it is all right. The equation gives the center of mass as a function of time.
  6. Apr 3, 2012 #5
    Ok cool. Thanks for your help. By the way.. Roshan from DotA? :wink:
  7. Apr 3, 2012 #6
    Yes. DotA 2 now.
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