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Homework Help: Location of zero net electric force

  1. Sep 22, 2008 #1
    1. The problem statement, all variables and given/known data

    Particle 0 experiences a repulsion from particle 1 and an attraction toward particle 2. For certain values of d_1 and d_2, the repulsion and attraction should balance each other, resulting in no net force. For what ratio d_1/d_2 is there no net force on particle 0?
    Express your answer in terms of any or all of the following variables: k, q_0, q_1, q_2.

    2. Relevant equations

    electric force F = kq_1q_2/r^2 where k = 9*10^9, q_1 and q_2 represent charges in coulombs and r is distance in meters between point charges

    Fnet = sqrt(F1^2 + F2^2) where F1 is repulsive force and F2 is attractive force

    3. The attempt at a solution

    Fnet = sqrt(F1^2 + F2^2)
    0^2 = F1^2 + F2^2
    -F2^2 = F1^2
    -[(k*q_2*q_0)/(d_2)^2] = [(k*q_1*q_0)/(d_1)^2]
    -(d_1)^2/(d_2)^2 = (k*q_1*q_0)/(k*q_2*2_0)
    -d_1/d_2 = sqrt(q_1/q_2)
    d1_1/d_2 = -sqrt(q_1/q_2)

    correct ratio?

    Attached Files:

  2. jcsd
  3. Sep 22, 2008 #2


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    There shouldn't be a negative sign when you're considering distance instead of displacement.
  4. Sep 22, 2008 #3
    so aside from the negative sign, the ratio of d1_1/d_2 = sqrt(q_1/q_2) is correct?
  5. Sep 22, 2008 #4


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  6. Sep 22, 2008 #5
    okay thanks for the help
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