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Homework Help: Basic particle accelerator - escape speed (grade 12)

  1. Feb 16, 2016 #1
    1. The problem statement, all variables and given/known data
    The device has two parallel plates, one positively charged and one negatively. The positive plate has a hole to allow electrons to fire out of it.

    b) How can the device be modified to accelerate protons?
    c) How does the escape velocity of a proton compare to that of an electron, if the electric field were the same? Explain.

    2. Relevant equations
    a = qε/m

    3. The attempt at a solution
    Part c is what I'm unsure about. Are they assuming that I've modified the device, but the electric field has the same magnitude?

    If so, my educated guess is as follows:

    The particles have equal but opposite charges and experience the same field, but a proton has a larger mass and will be accelerated less before exiting the device; therefore, it will have a lower exit speed.

    On the other hand, assuming the device has not been modified, the proton would still have a lower exit speed (probably won't exit at all) because it's attracted to the negative plate.
  2. jcsd
  3. Feb 16, 2016 #2


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    You're doing fine. Yes, part c question comes after the modification. (otherwise the protons would indeed go the other way and fall on to the negative plate).
  4. Feb 16, 2016 #3
    Thank you,
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