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Homework Help: Accelerating electrons

  1. Mar 6, 2007 #1
    1. The problem statement, all variables and given/known data
    An electron is accelerated from rest through a potential difference of V volts. What is the final velocity?

    I did:
    [tex]qV=\frac{mc^2}{\sqrt{1-\frac{v_f^2}{c^2}}}[/tex]

    And solve for v, but I get an unreal answer. What am I doing wrong?!

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 6, 2007 #2

    hage567

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    Why are you using relativistic energy?
     
  4. Mar 6, 2007 #3
    Because there is an high potential difference. If I use non-relativistic energy it gives a speed higher than the speed of light. :rolleyes:
     
  5. Mar 6, 2007 #4

    hage567

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    Could you post more of the question and your work?
     
  6. Mar 6, 2007 #5
    If I'm not mistaken(Memory sometimes betray me) qV=(Gamma-1)mc^2
     
  7. Mar 6, 2007 #6
    ziiad this is the relativistic kinetic energy, what I need is the relativistic change in kinetic energy.
     
  8. Mar 6, 2007 #7
    No, you are right. What a stupid mistake of mine. :( Thanks, mate.
     
  9. Mar 6, 2007 #8
    Don't worry, we all make mistakes, they key part was "...accelerated from rest..."
     
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