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Help with energy momentum relation.

  1. Jul 20, 2011 #1

    I needed to derive a few equations using relativistic kinematics and I needed help with this simple equation.


    Basically I need to write the p^2c^2 part in terms of mass and c, in other words, what is p equal to without E being in the equation?

    Attached Files:

  2. jcsd
  3. Jul 20, 2011 #2
    p=m0*v/Sqrt[1-v^2/c^2], m0 is the rest mass.

    For anything more, you'll have to let us know where you're trying to get to (i.e. the equations you want to derive).
  4. Jul 20, 2011 #3

    I http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/relmom.html" [Broken] that (pc)2 = (mc2)2 - (mo2c4)

    So would this be correct?

    E = ((moc2)2 + (mc2)2 - (mo2c4))1/2
    Last edited by a moderator: May 5, 2017
  5. Jul 20, 2011 #4


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    Staff: Mentor

    Yes, but it doesn't say anything really new. The first and last terms in that equation cancel. After you do that, what do you have left? :smile:
  6. Jul 20, 2011 #5
    E=\gamma m_0c^2
    (pc)^2=E^2-(m_0 c^2)^2
    Make the appropriate substitution.
  7. Jul 20, 2011 #6
    Thanks for the help thus far. The page I'm looking at is http://teachers.web.cern.ch/teachers/archiv/hst2002/bubblech/mbitu/applications_of_special_relativi.htm" [Broken] and I'm trying to derive the general equation for an elastic collision. So far I have the following solved, please check my math. It's a little blurry, sorry!


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    Last edited by a moderator: May 5, 2017
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