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Homework Help: Velocity of Three Charges Released from Equilateral Triangle

  1. Mar 17, 2016 #1
    1. The problem statement, all variables and given/known data
    Three equal charges with charge q and mass m are placed into an equilateral triangle of side length L. Find the speed of each when they are infinitely far from one another.

    2. Relevant equations
    -ΔU =ΔK (since the electric force is conservative), U= 1/4πε Σq1q2 /r

    3. The attempt at a solution
    Since the charges are equal and in an equilateral triangle U =1/4πε (3q^2 /L). Conservation of energy gives that ΔK =U, since U at infinity is 0. By conservation of momentum each charge will move at the same velocity so 1/2mv^2 +1/2mv^2 +1/2mv^2 = 1.5mv^2 =U. Implying v = √(1/6πε [3q^2 /L]).
    Any errors in the above reasoning or a better way of laying out the solution?
  2. jcsd
  3. Mar 17, 2016 #2


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    Homework Helper

    It is correct, but you can simplify the result.
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