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Homework Help: Electron displacement between two parallel plates

  1. Feb 9, 2012 #1
    The problem is attached, stuck on part d.
    1. The problem statement, all variables and given/known data

    Im given a problem with two horizontal and parallel plates 8cm long 3cm away from each other. An electron is moving through them with a velocity V[itex]_{0}[/itex]. It is also given that the voltage across the plates is 20 Volts and the electron deflects upwards 1.2 cm.

    2. Relevant equations

    Ive done all the work for parts a, b, and c, which gave me a F[itex]_{electric}[/itex] of 666.67 V/m or 666.67 N/C down, and an acceleration of 1.17 * 10[itex]^{14}[/itex] m/s[itex]^{2}[/itex] up.

    3. The attempt at a solution

    I have no idea how to even come at this. The only idea I had without being given an initial velocity in any direction is something with the deflection of 1.2 cm, but I dont know how to use that without knowing the amount of time the electron spends between the plates.

    Thanks for ANY help.

    Attached Files:

    • 6 work.jpg
      6 work.jpg
      File size:
      30.1 KB
    • 6.png
      File size:
      69.6 KB
    Last edited: Feb 9, 2012
  2. jcsd
  3. Feb 9, 2012 #2


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    Staff: Mentor

    Hello SoundZombie. Welcome to Physics Forums.

    You've calculated an acceleration for the electron in the vertical direction, and you're given the vertical deflection that it experiences over its time between the plates. What can you make from that? What kinematic equation might apply?
  4. Feb 9, 2012 #3
    I knew I was overlooking something small. haha

    d[itex]_{y}[/itex]=v[itex]_{0y}[/itex]t+1/2a[itex]_{y}[/itex]t[itex]^{2}[/itex] which will end up being 1.2cm=(0)t+(1/2)(1.17*10[itex]^{14}[/itex]m/s[itex]^{2}[/itex])t

    Im still having a little trouble remembering all of these because I took Physics 1 about 4 or 5 years ago, and Im just taking Physics 2 now. Im trying to re-learn everything at once. Thanks for the quick reply. Youre a life-saver!
    Last edited: Feb 9, 2012
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