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Energy Conservation of an electron

  1. Apr 8, 2009 #1
    1. The problem statement, all variables and given/known data
    Determine the total energy of an electron traveling at 0.98 c

    A) 0.25 MeV
    B) 0.51 MeV
    C) 0.76 MeV
    D) 1.8 MeV
    E) 2.6 MeV

    2. Relevant equations

    KE = 1/2 mv^2
    E=mc^2 (rest energy)

    3. The attempt at a solution

    I had found the velocity for an electron by 0.98 * 3.0 *10^8. I squared that number and multiplied by the mass of the electron (9.11 * 10^-31 kg) then multiplied by 0.5

    This gave me 3.937 * 10^-14. I divided this by 1.6 * 10^-13 to get MeV which gave me an answer of 0.246 MeV. That would be answer A, but the correct answer was E.

    I also took into account for a possible Rest energy, which you would use E=mc^2. Adding up what I got for rest energy and my original answer which gave me A, resulted in the answer for C. I'm still not sure how the answer E came about.
  2. jcsd
  3. Apr 9, 2009 #2


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