# Homework Help: Need help with Columb law question.

1. Aug 24, 2006

### nateastle

I belive this is the right place for this question. I am strugling with getting this homework problem setup. The question is:

A charge q1 = -3 nc is placed at the origin of an xy-cordinate system, and a charge q2=2.00nC is placed on the positive y Axis at y=4cm. If a third charge q3 =4nC is now placed at point x=3 cm, y=4cm, find the x and y componets of the total force exerted on this charge by the other two.

I have setup my grid and figured out the force on the y Axis is -3.45 X 10^-5 (or at least I hope that is correct) but I am having problems figuring out how to setup the problem to get the force on the x axis. If I didn't calculate the force right for the y axis please let me know. I have been using coulombs law of f=k(q1q2/r^2)

2. Aug 24, 2006

### Andrew Mason

Your answer for the force on the y axis is correct, in Newtons. The force in the +x direction is the force between charge 2 and 3 less the x component of the force between 1 and 3 (which is in the - x direction). I get about 5.4 x 10-5 N. in the + x direction.

AM

3. Aug 25, 2006

### nateastle

thank you for the help.