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Homework Help: Parallel Plates - Electron Liberation

  1. Jan 13, 2010 #1
    1. The problem statement, all variables and given/known data
    Hello, I wonder if anyone could check my answer to this problem.

    Thanks in advance

    An electron is liberated from the lower of two parallel plates separated by a distance of 5mm. The upper plate has a p.d. of 1000v relative to the lower plate. How long does it it take for the electron to reach to upper plate.

    2. Relevant equations
    f=ma, f=qe, e=v/d

    3. The attempt at a solution
    I said F=ma=QE therefore QE=ma and since E=V/d=1000/0.005=2x105


    Then using s=ut+1/2at2, t=5.335x10-10s.

    Thanks again for any help

    Last edited: Jan 13, 2010
  2. jcsd
  3. Jan 13, 2010 #2
    i would take

    ma = relativistic mass * dv/dt = qE

    solve for v and find time taken
  4. Jan 13, 2010 #3
    Hello, thanks for your response.

    Is that differentiation? Not too sure about how to do that.

    Any chance you could get an answer from your method and compare it to mine.

    Thanks again,

  5. Jan 13, 2010 #4
    4.5*10^-11 s

    try it, its really simple
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