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Homework Help: Relativistic Energy Problem

  1. Nov 26, 2013 #1
    1. The problem statement, all variables and given/known data
    In the reference frame S', two protons, each moving at .5c, approach each other head on. Calculate the total kinetic energy of the two protons in frame S', and calculate the total kinetic energy of the two protons as seen in reference frame S which is moving with one of the protons.

    3. The attempt at a solution
    So for the first part apparently the answer i'm looking for is 290MeV

    v = .5c so γ = 1.1547

    using 1/2 mv^2
    m = 1.6726E-27
    v = .5(3E8)

    and then multiplying this times two for two protons and 1.15 from gamma, then converting that to eV by 1J = 6.24E18 eV I get 270MeV.. back of the book says 290 MeV.. what am I doing wrong ;-(?
  2. jcsd
  3. Nov 26, 2013 #2


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    Homework Helper
    Gold Member
    2017 Award

    You'll need to use the relativistic formula for kinetic energy.
  4. Nov 27, 2013 #3
    However we will not provide it. lol
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