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## Homework Statement

A point charge +2Q is at the origin and a point charge -Q is located along the x-axis at x=d. Find a symbolic expression for the net force on a third point charge +Q located along the y-axis at y = d

Answer = [tex]k\frac{Q^2}{d^2}<\frac{1}{2\sqrt{2}}, 2 - \frac{1}{2\sqrt{2}}>[/tex]

Below is a Picasso of what is going on

[PLAIN]http://img708.imageshack.us/img708/842/25027988.jpg [Broken]

## The Attempt at a Solution

I define the charge at the origin, +2Q, to be 1 and the -Q at x = d to be 2 and Q at y = d be 3

[tex]F_{3} = F_{13} + F_{23}[/tex]

(1) [tex]F_{13} = k\frac{2q^2}{d^2}<0,1>[/tex]

(2) [tex]F_{23} = -k\frac{q^2}{2d^2}<-1,1>[/tex]

So the sum of (1) and (2) is then [tex]k\frac{q^2}{d^2}<\frac{1}{2},-\frac{1}{2}>[/tex]

(1), I had q

^{2}because they use q as a common

(2)I had a - in front of k because it is a negative and positive charge interaction. The <-1,1> indicates that the "slope" of the vector is negative.

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