Electric force due to point charges

[dgreen]

Homework Statement

3 point charges are fixed in place in the right triangle shown below, in which q1= 0.67 microC and q2= -0.67 microC. What is the electric force on q3 with +1.0 microC due to the other two charges?
Magnitude?
direction, measured counterclockwise from the +x axis?

**HYP=10cm or .1m (q1-q3)
**Opp=8cm or .08m (q1-q2)

Homework Equations

[k (q1) (q1)]/d^2
k= 8.99e9

The Attempt at a Solution

f13= (8.99e9 * .67e-6 * 1e-6)/ .1^2 <-- shouldn't this provide the magnitude from q1 & q2 on q3?

 

[jbsteele]

f23= (8.99e9 * -.67e-6 * 1e-6)/ .08^2 <-- and this for q2 & q3?Total F = F13 + F23 = 4.7 x 10^-5 Ntan theta = y/x = .08/.1 = .8theta = 53.1 degrees (counterclockwise from +x axis)