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Physics Electric Field Problem

  1. Feb 16, 2013 #1
    1. The problem statement, all variables and given/known data
    A particle with a mass m and a charge Q is accelerated through a potential difference V, causing its kinetic energy to increase by an amount K. Another particle of mass m/5 and charge 2Q is accelerated through the same potential. How much kinetic energy does this second particle gain?


    2. Relevant equations
    Vq = U

    (1/2)mv^2 = U;


    3. The attempt at a solution
    I can't find an equation that relates mass, charge and kinetic energy. Any help would be appreciated.
     
  2. jcsd
  3. Feb 17, 2013 #2

    NascentOxygen

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    It seems that you don't need to involve mass.

    Remember, 1 volt = 1 joule of energy per coulomb
     
  4. Feb 17, 2013 #3
    If Q*C = K;
    then 2Q*C = 2K'

    So the increase in kinetic energy is K, correct me if I'm wrong.
     
  5. Feb 17, 2013 #4

    haruspex

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    I think you mean 2Q*C = K'
     
  6. Feb 17, 2013 #5
    Then the kinetic energy doesn't change?
     
  7. Feb 17, 2013 #6

    haruspex

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    K' stands for the KE of the 2Q charge, right? (Just noticed the OP uses V, not C, so switching back to that here...)
    If Q*V = K and 2Q*V = K' then what is the relationship between K and K'?
     
  8. Feb 17, 2013 #7
    So K' = 2K, right, because Q is proportional to KE.
     
  9. Feb 17, 2013 #8

    NascentOxygen

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    Right, because KE is proportional to Q here.

    Remember, 1 volt = 1 joule per coulomb
     
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