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Electrostatics/Coulumb's Law

  1. Mar 7, 2008 #1
    1. The problem statement, all variables and given/known data
    Two identical point charges (Q=3uC) are situated 60cm apart on the y-axis equidistant from the origin. A 2uC point charge lies at 40cm on the + x-axis. What is the magnitude and direction of the net force on the 2uC charge.

    2. Relevant equations
    F= kq(1)q(2)/r^2

    3. The attempt at a solution
    i figured the force between the two charges on the y-axis to be .225N using the above equation, but i do not see how that value is going to have any affect on the 2uC charge.
  2. jcsd
  3. Mar 7, 2008 #2
    use superposition

    if you draw lines from each Q to the 2uC you will see you have a triangle in order to find the force effecting 2 you need to use that diagonal length as R for F=KQQ/R^2 you will be able to find this pretty easily because you'll see the right triangle forming at the origin.

    The value from each will be the same because the distance is the same, so you should find that its just twice as large as one side.
  4. Mar 7, 2008 #3


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    HINT: What does the principle of superposition say?

    Edit: Beaten to it ...
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