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Homework Help: Finding charges on an equilibrium position

  1. Jan 20, 2009 #1
    1. The problem statement, all variables and given/known data

    http://img214.imageshack.us/img214/4430/fieldoc3.th.jpg [Broken]

    E = (3.00i+5.00j) x 10^5 N/C the ball is at equilibrium at 37 degrees, the ball has a mass of 1 gram. What is the charge of the ball? What is the tension of the string?

    2. Relevant equations
    E = Fe/q0

    3. The attempt at a solution

    As far as I know to solve for this problem Fe must be equal to 0?

    Or we should first resolve the forces acting on the ball, which is

    T cos(37) - mg = 0.. am I right? I don't know what's next
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 21, 2009 #2


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    Science Advisor
    Homework Helper

    So in this type of problems, you always treat the horizontal and vertical components separately. Or, in this case, you would use components along and perpendicular to the string.

    Let's start by identifying all the forces working perpendicular to the string.
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