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Homework Help: Internal Energy of an Electron

  1. Dec 7, 2015 #1
    1. The problem statement, all variables and given/known data
    What is the internal energy of an electron moving at 0.750c0 in the Earth reference frame?

    2. Relevant equations

    3. The attempt at a solution
    E = mc^2
    E = (9.11 * 10^-31)(.750)(3*10^8)

    However, this appears incorrect. What have I done wrong or what am i missing?
  2. jcsd
  3. Dec 7, 2015 #2
    What do you mean "internal" energy? It's just one particle, so the options are "rest energy", "kinetic energy" and "total energy".
    If m is the mass of an electron, c is light speed, and v is the speed of the electron, then:

    Rest energy is [tex] E=mc^2 [/tex]
    Total energy is [tex] E_T = \frac{mc^2}{ \sqrt{1 - \frac{v^2}{c^2}}} [/tex]
    Kinetic energy is [tex] KE = E_T - E [/tex]
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