# Homework Help: Coulomb's law in 3D

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1. Jun 5, 2017

### Sofia Matthews

1. The problem statement, all variables and given/known data
q1= 5 x 10^-6C position (1;2,-1)
q2= -3 x 10^-6 C position (-2,1,3)

a) what is the electric force caused by q2 on q1? (vector notation)
b) what is the electric field at (0,0,0)

2. Relevant equations
F = kq1q2/r^2
E= F/q

3. The attempt at a solution
I really don't know how to start this problem. Since this problem is in 3D, I don't know how to find the z coordinate of the electric force.

What I initially did was to find the electric force with Coulomb's law, but it gives me a number and not components. I tried to play with Pythagoras's theorem, but didn't figure anything out.

Last edited: Jun 5, 2017
2. Jun 5, 2017

### cnh1995

Welcome to PF!
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3. Jun 5, 2017

### haruspex

In terms of the positions P and Q of two charges, what is the line of action of the force between them?