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Homework Help: Distance of Electrons with Electrostatic Force

  1. Feb 5, 2012 #1
    1. The problem statement, all variables and given/known data
    How far apart must two electrons be placed on the Earth's surface for there to be an electrostatic force between them equal to the weight of one of the electrons?

    2. Relevant equations

    Fe = (1 / 4∏ε0) X (q1q2 / r^2)

    3. The attempt at a solution

    I set Fe = me- (electrical force = mass of electron).

    and solved for r = sqrt( q^2 / (me-)(4∏ε0) ) = 15.98 m, but the answer should be 5.08 m..
  2. jcsd
  3. Feb 5, 2012 #2


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    Science Advisor
    Homework Helper

    hi kgal! :smile:
    hmm … 15.98/5.08 = π …

    did you lose a π somewhere?​
  4. Feb 5, 2012 #3
    The WEIGHT of an electron = me x 9.81, I got the answer to be 5.02m
  5. Feb 5, 2012 #4
    i attached the picture.

    I don't see the flaw...

    Attached Files:

  6. Feb 5, 2012 #5
    thanks technician!

    i thought that i have to ignore g because its so small compared to the electrical forces...
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