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Homework Help: Magnitude and direction of the Electrostatic Force

  1. Mar 29, 2012 #1
    1. The problem statement, all variables and given/known data

    3 identical charges of 2.0 uC are placed on the x-axis. The first charge is at the origin, the second to the right at x = 50cm, and the third is at the 100 cm mark. What are the magnitude and direction of the electrostatic force which acts on the charge at the origin?

    2. Relevant equations

    F = k Q1Q2/r^2

    3. The attempt at a solution

    F12 = (9.0e9 * 2.0e-6 * 2.0e-6) / 1m^2 = .036N

    F13 = (9.0e9 * 2.oe-6 * 2.0e-6) / 0.5m^2 = .144 N

    Magnitude = .036 + .144 = .18 N

    Direction = I have no clue. If they are all identical wouldn't they all repel each? Wouldn't that make the overall direction to the left since each charge repels the charge at the origin.

    Thanks for the help!
    Last edited: Mar 29, 2012
  2. jcsd
  3. Mar 29, 2012 #2


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    Staff: Mentor

    Hi wrenegade, welcome to Physics Forums.

    If they all repel each other, in what direction is the charge at the origin going to want to move? What then is the direction of the net force on it?
  4. Mar 29, 2012 #3
    The charge on the origin would want to move left, correct? Making left the overall direction of the net force.
  5. Mar 29, 2012 #4


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    Staff: Mentor

    Sounds good :smile:
  6. Mar 29, 2012 #5
    Thank you very much!
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