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Homework Help: Point charge, proton placement, x-, y-axis

  1. Sep 26, 2009 #1
    1. The problem statement, all variables and given/known data
    A point charge q = -0.368 nC is fixed at the origin. Where must a proton be placed in order for the electric force acting on it to be exactly opposite to its weight? Let the y axis be vertical (positive up and negative down) and the x axis be horizontal (positive to the right and negative to the left. Enter the x-value first and then the y-value.

    2. Relevant equations
    mass of proton = 1.67e-27 kg
    charge of proton = 1.60e-19 Coulombs

    3. The attempt at a solution
    electric force = weight?
    [(8.9e9 Nm^2/C^2)(1.6e-19 C)(-0.368e-9 C)]/[r^2] = (1.67e-27 kg)(9.80 m/s)
    solve for r. r = 5.66e3

    But I don't know if this is supposed to have units since it needs to be positions on an x and y axis and I also don't know how you're supposed to end up with 2 values. Thanks in advance!
  2. jcsd
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