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Physics Electric Field Problem

  1. Feb 17, 2013 #1
    1. The problem statement, all variables and given/known data
    k = 9 * 10^9

    Sphere A of mass m = 0.0004 kg holds a positive charge qA = 3.0 10^-5 C and is fixed in place. Point P is d = 0.03 meters away from Sphere A.

    Sphere B is identical in mass to sphere A, but carries a charge of qB = 3.6 10^-5 C. Sphere B is brought from a distant location and fixed at point P.

    Frensley_E-Potential_Points_009b.gif

    If both spheres are released from rest at the same time, how fast do the spheres move when they are very far apart?

    2. Relevant equations
    KE = (1/2)mv^2
    KE = qV

    3. The attempt at a solution

    I keep getting different speeds for each ball using the first equation, any help would be appreciated.
     
  2. jcsd
  3. Feb 17, 2013 #2

    haruspex

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    Pls post your working, as per forum rules.
     
  4. Feb 17, 2013 #3
    I'm not sure if I have to get the velocity of ball a or ball b, or get them both and average, I just need help on this part of the problem.
     
  5. Feb 18, 2013 #4
    I'm not sure if I have to get the velocity of ball a or ball b, or get them both and average, I just need help on this part of the problem.
     
  6. Feb 18, 2013 #5

    haruspex

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    They're the same mass. What does conservation of momentum tell you about the relationship between their velocities?
     
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