# I need some guidance on my coulomb's law homework.

1. Sep 9, 2012

### name of user

1. The problem statement, all variables and given/known data
two charged particles held fixed in the xy plane are: q1= +3.0 μC, x1=3.5 cm, y1= 0.50 cm, and q2= -4.0 μC, x2= -2.0 cm, y2= 1.5 cm.

(question 1) What is the magnitude and the direction of the electrostatic force on q2. ?

(question 2) Where would a third charge q3= +4 μC be placed so that the net electrostatic force on q2 is zero?

2. Relevant equations
For question one i came out to 0.025N @144° ccw
is that even remotely correct?

3. The attempt at a solution
I don't want the answer, i would like to just know the steps so that i can try it for myself.
Ive added the x's amd y's and came out with

Ʃ x= 0.035-0.02= 0.015
Ʃ y= 0.005+0.015=.02

from here what can i do ?
could i just inverse the angle from q2 to find the position?

2. Sep 10, 2012

### CAF123

Can you show your working for how you get 0.025N at 144o counterclockwise?

3. Sep 10, 2012

### SammyS

Staff Emeritus
Why are you adding the x coordinates and adding the y coordinates ?

The distance between points, (x1, y1) and (x2, y2) is $d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}\ .$