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Homework Help: Two particles collide, COM frame, relativistic velocities.

  1. Mar 2, 2016 #1
    1. The problem statement, all variables and given/known data
    2-body, COM frame collision
    a+b ---> c+d
    E = Ea+Eb = Ec+Ed
    Show that
    dE/dPf = Vc+Vd
    Show that the answer is the same when the velocities are relativistic
    I don''t know how to work out the relativistic aspect of the question.
    2. Relevant equations

    3. The attempt at a solution
    E = Pc^2/2Mc - Pd^2/2Md
    (Pf^2)/2(I/Mc + I/Md) = (Pf^2)/2(Md+Mc/McMd)
    dE/dPf = Pf(1/Mc+I/Md) = Vc + Vd
  2. jcsd
  3. Mar 2, 2016 #2


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    2017 Award

    Staff: Mentor

    What is Pf?
    How can E depend on anything if it is fully determined by the initial (or final) state?

    If you can solve it in the Newtonian case, replace all Newtonian equations with their relativistic versions, and see if it still works.
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