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Homework Help: Coulombs Law

  1. Sep 13, 2008 #1
    1. The problem statement, all variables and given/known data
    Given a cube with equal charges on all corners save one, find the charge on the origin.
    http://img79.imageshack.us/img79/4968/cubekg7.jpg [Broken]

    2. Relevant equations
    F = kQ1Q2

    3. The attempt at a solution
    My current idea is splitting up the magnitude of all charges on the origin into their X,Y, and Z components.

    Because all magnitudes are formed with right triangles I can use pythagorean theorem to solve for the components and I get:

    Q1: +1 in the X
    Q2: +1 in the Z
    Q3: +1 in the Y
    Q4: +1 in the X, Z
    Q5: +1 in the X, Y
    Q6: +1 in the Y, Z
    Q7: +1 in the X, Y, Z

    So the sum of the magnitudes acting on the origin would be +4 in all directions, and I have a feeling this is wrong.
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Sep 14, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi Cefari! :smile:

    I don't understand either the question or your answer. :confused:

    Do you mean find the field at the origin?

    If you're adding fields, remember that they're vectors (with a direction), and the strength is 1/distance-squared.
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