Coulomb's law; vector form problem

[Dogger]

Homework Statement

3 charges are placed like shown:

Q1 __4cm____ Q2 ______6cm___________Q3
Q1=-2nC
Q2= 1nC
Q3= 3nC
Find the resultant force and its direction upon the charge Q3.

Homework Equations

F=k0*(Q1Q2)/r2
k0-constant, equals to 9*10^9
r-distance

The Attempt at a Solution

F1,2=9*10^9*(-2*10^-9*3*10^-9)/(4*10^-2)^2=-11.25*10^-6
F2,3=7,5*10^-6
F1,3=-5,4*10^-6
F(resultant)= 7,5-11,25-5,4 (*10^-6)= -9,15 *10^-6

 

[TSny]

Welcome to PF!

Does the force F1,2 act on Q3?

Be sure to include units in your answer.