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K3nt70

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**[SOLVED] Two point charges, Zero Net Force**

## Homework Statement

Two point charges of charge 7.40 μC and -1.80 μC are placed along the x-axis at x = 0.000 m and x = 0.300 m respectively. Where must a third charge, q, be placed along the x-axis so that it does not experience any net force because of the other two charges?

## Homework Equations

F = k[tex]\frac{Q1 Q2}{x^{2}}[/tex]

## The Attempt at a Solution

im fairly sure i know what to do, but my answer is wrong. It basically looks like this:

-k[tex]\frac{q1}{(0.3 - x)^{2}}[/tex] = k[tex]\frac{q2}{x^{2}}[/tex]

and then i just fill in the two charges, (coulomb's constant cancels) and solve for X. It comes out to a quadratic equation which isn't a big deal; my positive answer is 2.41E-1 m (which is incorrect).

heres a diagram:

http://img356.imageshack.us/img356/2918/72794740cx4.png [Broken]

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