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Homework Help: Tension And Electric Charge

  1. Jul 6, 2006 #1

    I thought I did this correctly and my answer turned out incorrect. Here's the problem:

    http://synthdriven.com/images/deletable/help.jpg" [Broken]

    This is what I did:

    In order to use Coloumb's Law, I need r, the distance between the two charges.


    So that's r.

    Then I need to pick one side of this thing apart and break it down into x and y-components.

    With the weight, I have three forces acting on this thing. The tension in the rope, the weight, and the electrical force repelling each sphere.

    My goal is to find the x-component of the electrical force so I can then plug it into Coulomb's law and find the charge.

    For the weight,

    For the tension,

    For the electrical force,

    To find T, all I did was:

    (net force of y-component)


    So for T, I get 0.098239

    Plugging that into Tx, I get 0.006853

    And then it goes into Coulomb's law. Which I have reformatted this way:


    ...Because both charges are supposed to be equal...

    Moving that around, I get:

    Plugging in values, I got 1.711e-7

    What did I do wrong?
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Jul 6, 2006 #2

    Doc Al

    User Avatar

    Staff: Mentor

    That first equation should have sin(4), not arcsin(4).
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