Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Help with energy momentum relation.

  1. Jul 20, 2011 #1
    Hi,

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

    attachment.png

    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
    Sure,

    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

    jtbell

    User Avatar

    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
    [tex]
    E=\gamma m_0c^2
    [/tex]
    and
    [tex]
    (pc)^2=E^2-(m_0 c^2)^2
    [/tex]
    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!

    attachment.php?attachmentid=37377&stc=1&d=1311222833.jpg
     

    Attached Files:

    Last edited by a moderator: May 5, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook