# Field and force with three charges

## Homework Statement

At a particular moment, three small charged balls, one negative and two positive,are located as shown in the figure. q1 = 3 nC, q2 = 7 nC, and q3 = -5 nC.

What is the electric field at the location of Q1, due to Q2?

y
q1
|
|
|
q2______q3____x

Okay that is the given diagram the if q2 is at (0,0) then q1 is at (0,4); q3 at (3,0);
and the distances are in centimeters

## Homework Equations

I'm using Coulomb's Law which states that E = 9e9*(q/r^2)r-hat

## The Attempt at a Solution

So I thought all I have to do is plug in the values

[9e9*(7e-9/(.004)^2)]*<0,4,0> = <0,3937500,0>N/C

please help me, I've been starring at this for a while and I cannot figure out why I don't get the right answer, I shouldn't have to consider the other charges because they don't affect the field created by q2 just the net field, so why is this not correct I have no idea.

Thanks Again for all the help guys

ehild
Homework Helper
In what units are the components of the position?

ehild

The components of the positions are in centimeters. (cm)

ehild
Homework Helper
If so, 4 cm = 0.04 m. And you have to use the unit vector in the direction of <0,4,0>.

ehild

Oh yes your right, I just kept converting the cm to m wrong, putting an extra zero in front of it like they were mm or something. Thank You so much it really helps having someone else look at this. I knew I had to be making some stupid mistake.