Finding Charge on a Cube Corner

[Cefari]

Homework Statement

Given a cube with equal charges on all corners save one, find the charge on the origin.
http://img79.imageshack.us/img79/4968/cubekg7.jpg

Homework Equations

F = kQ₁Q₂

The Attempt at a Solution

My current idea is splitting up the magnitude of all charges on the origin into their X,Y, and Z components.

Because all magnitudes are formed with right triangles I can use pythagorean theorem to solve for the components and I get:

Q1: +1 in the X
Q2: +1 in the Z
Q3: +1 in the Y
Q4: +1 in the X, Z
Q5: +1 in the X, Y
Q6: +1 in the Y, Z
Q7: +1 in the X, Y, Z

So the sum of the magnitudes acting on the origin would be +4 in all directions, and I have a feeling this is wrong.

 

[tiny-tim]

Hi Cefari!

I don't understand either the question or your answer.

Do you mean find the field at the origin?

If you're adding fields, remember that they're vectors (with a direction), and the strength is 1/distance-squared.