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Homework Help: Finding the velocity of two charges

  1. Sep 26, 2016 #1
    1. The problem statement, all variables and given/known data
    If two particles were allowed to move freely, how fast would they be going at the instant they collide or when they're infinitely far apart? Explain Carefully.

    There are no initial velocities given. The charges are -4 nC and 3 nC and each has a mass of 7 mg.

    2. Relevant equations

    3. The attempt at a solution
    I don't really know how to solve this or go about it. At first, I thought it would be zero, because all of it's kinetic energy are converted into potential energy the instant they collide. But then, I feel like this question isn't that simple at all. If there was some velocity to the particles, I don't know how to find it or what formulas/equations to do it.
  2. jcsd
  3. Sep 26, 2016 #2


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    Staff: Mentor

    Is that the entire question statement word for word?

    It seems that the problem is greatly underspecified. We aren't told anything about the initial conditions, either their separation or velocities. We aren't told how large the particles are so we can't tell what a "collision" entails --- how close can they get center to center before they touch?

    Perhaps you are expected to invent a plausible scenario and work out the details symbolically?
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