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Homework Help: Special Relativity, equation help needed

  1. Jul 22, 2010 #1
    Given that E2 = c2p2 + mo2c4-----------(1);
    where p represents the relativistic momemtum p=[tex]\gamma[/tex]mou,
    show that m=(p2c2-T2)/(2Tc2) where m is the relativistic mass of the particle,and T it's kinetic energy.

    2. Relevant equations

    E= T+moc2-------(2)

    3. The attempt at a solution

    I start by saying p2c2= E2-mo2c4 (from (1)), subtracting T2 from both sides gives
    p2c2 -T2 = E2-mo2c4-T2 . Now using (2) i expand E;

    p2c2 -T2= (T+moc2)2-mo2c4 -T2 which gives
    p2c2 -T2= T2+2Tmoc2+mo2c4 -mo2c4 -T2; simplifying

    p2c2 -T2 = 2Tmoc2 Now dividing by 2Tc2 gives

    (p2c2-T2)/(2Tc2) = (2Tmoc2)/(2Tc2) I now have the required LHS of (1),

    This yields (p2c2-T2)/(2Tc2) = mo , NOT m !!!!!!!

    Where have i gone wrong !!!??
  2. jcsd
  3. Jul 22, 2010 #2


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    Your work looks fine to me. The problem appears to be wrong.
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