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**1. Homework Statement**A charge of +2 Q (A)is placed at the origin of a coordinate system and a charge of - Q (B) is placed at a distance d from the origin. How far from the origin must have 3rd charge +Q (C) be placed so that the net force on it is zero newtons.

**2. Homework Equations**

Fe=kQq/r^2

**3. The Attempt at a Solution**

The solution to this question says that the Third charge must be placed greater than 2d distance away from the origin.

I tried to solve this problem by finding a distance that would make the absolute value of the force of A on C equal the force of B on C. Making the distance that the Third charge is place morevthan 2d just does not make these forces on C equal. For example placing the Third charge at 3D makes the charge A on C : B on C have the ratio of 2/9d^2 : 1/4d^2. That doesn't seem to make the net force on charge C = zero to me

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