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Homework Help: Electric Forces and Coulomb's Law Problem

  1. Jan 26, 2012 #1
    1. The problem statement, all variables and given/known data
    In the figure, the net electrostatic force on charge Q2 is zero. If Q1 = -5 nC and Q2 = +7 nC, determine the magnitude of Q0.

    2. Relevant equations
    F = (k*q1*q2)/d^2

    3. The attempt at a solution
    I notice that Fnetx and Fnety for Q2 are the same.
    So I write,
    Fq1*cos(theta) + Fq1 sin(theta) - Fq0(.707) = 0
    k*q1*q2/d^2*(cos(theta) + sin(theta)) = k*q2*q0/x^2*(.707)
    then after some algebra I get,
    [q1*x^2*(cos(theta) + sin(theta))]/(d^2*.707) = Q0

    I am questioning my method here, but this is what I have done so far.
  2. jcsd
  3. Jan 26, 2012 #2
    Sorry, d is the distance between q1 and q2
    x is the distance between q0 and q2
  4. Jan 26, 2012 #3
    It's funny how when I'm writing how I attempted the solution I get a moment of clarity and I figure out the problem. Thanks anyways, I got it!
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