# Coulomb's Law in 2D Question

1. Jul 19, 2008

### cobhc27

1. The problem statement, all variables and given/known data

Consider the arrangement of point charges shown below. Calculate the net force on point charge 1 given the arrangement of the point charges and the separation of the charges.

1=2=3=e-
2=e+
r=0.4cm
=0.0004m
K=9x10^9
Fnet=?

Please use this link for an image of the "point charges shown below"
http://i277.photobucket.com/albums/kk71/cobhc_27/physics101.jpg

2. Relevant equations

Fnet=
Kq1q2
r^2

3. The attempt at a solution

Fnet=
Kq1q2
------
r^2

=
kq^2
-----
r^2

I assume you have to solve for 1 2 3 and 4 in this case, but I don't have a great idea on how to. From there, perhaps you add up each net force (but I don't know how to incorporate the 2d part). Any help given is greatly appreciated.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jul 19, 2008

### Knissp

Remember that force is a vector. To add vectors (in two-dimensions or in n-dimensions), add the components of the vector. The components can easily be calculated using trigonometric ratios, especially since you know the angle.

Could you clear this up a bit? You have 2 twice.

3. Jul 19, 2008

### Fredrik

Staff Emeritus
It's pretty easy:

1. Calculate the force on 1 caused by 2.
2. Calculate the force on 1 caused by 3.
3. Calculate the force on 1 caused by 4.