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I Electric Potential Energy Problem. Intuition needed!

  1. Mar 3, 2016 #1
    There's this problem that was given in my physics class..
    "Three identical, negatively charged particles are situated at rest in a straight line, as shown below. All three are released simultaneously, and are free to move. Find the maximum velocities attained by particles A, B, and C. They have have a mass of 1.70 grams and a charge of -700x10-6C."
    The picture just has particles A, B , and C horizontal to one another with a distance of 2cm from A to B and 2 cm from B to C. Making the distance from A to C 4cm.
    I hope you guys can imagine the picture well enough its not too bad.
    Anyways, you solve for the total potential energy of the system and solve for the final velocity. I expected particle B, however, to have a final speed of zero, since it wouldn't move at all since it has an negatively charged particle to its right and left at the same distance that are identical. Apparently, that is wrong. Why does particle B move when it is EXACTLY in the middle of the other two? Also, in what direction would it move?
    Thanks a bunch! This question is driving me nuts.
     
  2. jcsd
  3. Mar 3, 2016 #2
    Are you sure, there's nothing more to the question?
     
  4. Mar 3, 2016 #3

    BvU

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    I expect idem. So who claims it's wrong ?
     
  5. Mar 3, 2016 #4
    Apparently B would have a speed the same as the particle that accelerates to the right which is also the speed of the particle that accelerates to the left.
    And theres nothing more to the question thats it.
     
  6. Mar 4, 2016 #5

    BvU

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    Well, given the 2 cm distances I wonder what the value of that speed is according to the "apparent" answer ?
     
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