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Homework Help: Three Charges in a Triangle

  1. Feb 18, 2008 #1
    1. The problem statement, all variables and given/known data

    Three electrons form an equilateral triangle 1.00 nm on each side. A proton is at the center of the triangle. What is the potential energy of this group of charges?

    2. Relevant equations

    U = K q1 q2 / r
    K = 9*10^9
    q = 1.6*10^-19

    3. The attempt at a solution

    First I made the triangle and tried to get the U of the three negative charges. I did (9*10^9)(1.6*10^-19)^2/(1*10^-9) and multiplied this by 3 because there are 3 different PE combinations with the negative charges and got 6.912*10^-19. Then i found it for the positive and negative charges and there are also 3 combinations for this. I calculated the distance from the negative to the positive charge to be .66 nm and then i used the same formula multiplied by 3 to get 1.05*10^-8.

    Now I tried adding the PE's together but the first number is negligible compared to the second. I'm not sure if I made a mistake in calculating the radius, or if there is another point I'm missing on how to figure out the total PE. Thanks in advance.
    Last edited: Feb 18, 2008
  2. jcsd
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