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Homework Help: Zero-momentum frame - total momentum in this frame

  1. Apr 10, 2014 #1
    1. The problem statement, all variables and given/known data

    Assume that all particles are non-relativistic, that the target X is initially at rest,
    and that x has kinetic energy Tx in the laboratory frame. Show that the total kinetic
    energy of the reactants in the centre-of-mass frame is given by T* = μTx/mx, where mx is
    the mass of particle x and μ the reduced mass of x and X. Also obtain an expression for
    p* in terms of T* and μ.

    2. Relevant equations

    I have completed the first part of this question without a problem. The second part, requiring p* to be found doesn't make sense to me. Surely the total momentum in the zero-momentum frame should be zero? Or is it expecting a different quantity?

    3. The attempt at a solution

    First part done. Second part - don't know what it is asking.
  2. jcsd
  3. Apr 10, 2014 #2
    I agree. The problem isn't clear. One possible interpretation is that p* is the momentum of the incoming particle - as opposed to total momentum - as seen in the center of mass ref. frame.
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