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Momentum of particle

  1. Dec 23, 2011 #1
    Say I have the rest energy(mc^2) and the total energy of a particle (E), would getting the momentum energy of the particle be as simple as doing (E^2-(mc^2)^2)^(1/2) = pc?

    And when accelerating a electron through a potential difference how would I work out its momentum, given I have its rest energy and the value for potential difference?

    Thanks.
     
  2. jcsd
  3. Dec 23, 2011 #2
    That looks like the correct equation to use.

    When an electron is accelerated through a potential difference, what happens to its total energy?
     
  4. Dec 23, 2011 #3
    c=1 you have
    E2= p2+m2

    so you want to know the momentum you do what you said

    p=√ [E2-m2]

    by the time you say "total energy E" it means that the kinetical energy is within your already known parameter, so is there a potential, is there not- you know E, you know mass, so you know its mommentum.
     
  5. Dec 23, 2011 #4
    I am assuming that for a p.d. of for example 1 MV, this will create an energy difference of 1 MeV for an electron and with the rest energy of around 0.5 MeV for an electron, it would simply equal 1.5 MeV/c for the momentum, but I think this is wrong, but I don't understand why.
     
  6. Dec 23, 2011 #5

    Matterwave

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    Assuming all the energy was kinetic, your formula works. If there is also potential energy involved, then you have to take that into account as well.
     
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