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Homework Help: Electric Force Act on Proton

  1. Mar 15, 2009 #1
    1. A proton has a mass 1.7x10^-27 kg and its speed is v=.969c. When an electric force acts on the proton and does 5.8x10^-9 J of work on the particle, what are the following values? A) Particle energy B) Particle Rest Energy C) Particle Momentum D) Particle Beta

    2. Particle energy=> E=(gamma)mc^2 ; Gamma=1/(sqrt(1-(beta^2)) ; Beta= v/c

    3. This problem is part of my study guide for a test. There was a whole other section that I completed before the professor threw in the part about the work done on the particle in which I had to find the original beta, gamma, energy and kinetic energy of the particle. I was able to do that successfully, but I don't understand how work done on a particle by means of electric force effects it's energy, rest energy, momentum, and beta. Thanks for your help! :)
  2. jcsd
  3. Mar 16, 2009 #2


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    Welcome to PF!

    Hi petalsweet! Welcome to PF! :smile:

    From the work-energy theorem: work done = change in KE …

    if the force is not conservative (eg, friction), work done = total energy lost

    but if the force is conservative (eg, gravity), no energy is lost, and the work done equals the PE, so we normally call it PE instead of work done :wink:

    anyway …
    work done = change in KE (either Newtonian or Einsteinian) :smile:
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