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Homework Help: Relativistic energy

  1. Sep 24, 2009 #1
    1. The problem statement, all variables and given/known data
    Energy of a particle may be of the form:

    [tex]E = \gamma mc^{2}[/tex]
    [tex]E = \sqrt{p^{2}c^{2} + m^{2}c^{4}}[/tex]

    Are both valid for every particle? matter and photon?
    Can they be equated?
  2. jcsd
  3. Sep 24, 2009 #2


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    Science Advisor
    Homework Helper

    Hi serverxeon! :smile:

    (have a gamma: γ and a square-root: √ :wink:)

    The first one doesn't work for m = 0 (a photon), since γ is not defined for v = c,

    but apart from that, yes, they're both valid for every particle. :smile:

    For m ≠ 0, you can prove the equivalence by using p = mvγ.
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