# Homework Help: Physics Electric Field Problem

1. Feb 16, 2013

### asheik234

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

Three charges are set in the plane of the page so that they form the vertices of a right triangle of lengths a = 3 meters, b = 4 meters, and c = 5 meters. The charges |Q1| = 2.40 10^-3 C and |Q2| = 1.80 10^-3 C have unknown sign. Charge q = -4. 10^-4 C has a total electric force F directed upward due to the other two charges.

Determine the magnitude of the electric field at the position of q due to the other two charges.

2. Relevant equations
k = 9 × 109 N m2/C2
E=kq/d^2

3. The attempt at a solution
I know that the charges Q1 and Q2 are negative, thus the electric field is going towards them, but I'm not sure what to do after this, any help would be appreciated.

2. Feb 16, 2013

### haruspex

Can you work out the force on q (magnitude and direction) due to each of Q1, Q2 separately?

3. Feb 16, 2013

### asheik234

Yes, I found the force from Q1 to be 1350000, and the force from Q2 to be 1800000. I'm not sure what to do after this though.

4. Feb 16, 2013

### haruspex

You have two forces, and you know their magnitudes and directions. Do you know how to add vectors?