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Homework Help: Coulomb's Law (Finding the force due to two other charge, not only one)

  1. Sep 26, 2008 #1
    1. The problem statement, all variables and given/known data
    In the figure below, determine (a) the electric force on 10 micro Coulomb due to other charges, and (b) the electric force on 2 micro Coulomb due to other charge

    2. Relevant equations
    Coulomb's Law

    Fe = kq1q2/D²
    k = 9.0 x 10^9

    3. The attempt at a solution

    I really don't know what to do since there are three charges and I should get the Fe due to other two charges. Should I get the Fe in each charge then subtract it? :confused:

    10 and 2

    Fe = 9x10^9(10x10^-6)(2x10^-6) / 0.005
    Fe = 36N

    Fe = 9x10^9(10x10^-6)(5x10^-6) / 0.005
    Fe = 90N

    Fe of 10micro Coulomb = 90 - 36 = 54N?

    I really don't know, but I'm trying my best.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

    Last edited: Sep 26, 2008
  2. jcsd
  3. Sep 26, 2008 #2
    Pick an origin first. It doesn't really matter where you place it, but I usually place it on the particle that you are trying to determine the E field for. This is a two dimensional problem, so determine the x- and y- components of the force on the particle due to each individual particle. To find the total force on the particle, add the x- and y-components together (principle of superposition); this gives you the force vector acting on the particle.
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