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Homework Help: Finding Q(point charge) with an angle, mass, and radii only

  1. Apr 29, 2010 #1
    1. The problem statement, all variables and given/known data
    To find the amount of static charge on the balls using coulomb's law and the concepts of equilibrium.

    r = 3.3 cm
    m1 = .085g
    m2 = .085g
    [tex]\vartheta[/tex] = 9.4[tex]\circ[/tex]

    2. Relevant equations

    F = K(q1)(q2)\r2

    3. The attempt at a solution
    I legitimately have no clue how to do this other than the fact that r = 9.4...
    Any tips/help will be appreciated.
  2. jcsd
  3. Apr 29, 2010 #2
    If you could post the actual question it would be helpful. You simply can't solve that with the information you provided.
  4. Apr 29, 2010 #3
    Sorry...but it's a lab so we don't have an actual question and we apparently have all the data we need. to solve for q.

    We have a hint that states, "Remember the key to solving the lab lies in figuring out the x and y vectors."

    I'm assuming parts of the vector is composed of gravity, tension, and the electric field which separated the balls from each other.
  5. Apr 29, 2010 #4


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    Homework Helper

    Let me guess: this lab involves hanging two balls side by side from a common pivot point, and measuring the angle that the strings make at the pivot. Yes? If so, start by drawing a free-body diagram for one ball, then writing out Newton's second law for both x and y directions.
  6. Apr 29, 2010 #5
    Yeah, that is exactly the lab we did. Thank you very much! I love this forum now.
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