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Homework Help: Zero momentum frame

  1. Feb 3, 2008 #1
    Could anyone quickly explain how the zero momentum frame works in 2 dimensional collision problems? I really don't understand at all.
  2. jcsd
  3. Feb 3, 2008 #2

    Shooting Star

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    Homework Helper

    There exists such a frame in which the vector sum of the momenta of all the particles is zero. If the ith particle has mass mi and velocity vi, then let v = ∑mivi/∑mi. A frame of reference travelling at this velocity v wrt the lab frame would be such a frame.

    For more convenience, you can consider it to be the non-rotating frame with origin at the centre of mass of the whole system and travelling at v.

    The total momentum in this frame is zero both before and after a collision.
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