How to calculate net force

[Kofyebs]

Homework Statement

Calculate the net force on A.[/B]

Homework Equations

F=k . (q1 q2)/r^2 , k=9 x 10^9 Nm^2/C^2[/B]

The Attempt at a Solution

(9*10^9 Nm^2/C^2)(1,4 x 10^-6C)(7,2 x 10^-6C) / 1,7mm^2
= 0,0313.
Could someone tell me what I am missing even if what i did is even correct.
Thanks[/B]

 

[Replusz]

That’s NOT how you do it!
You add:
F(B)=k (qA qB)/(AB)^2 and F(C)=k (qA qC)/(AC)^2
As I said before, you ’superpose’ (add) these 2 forces.
Do you understand now?

 

[Replusz]

F=(9*10^9 Nm^2/C^2)(1,6 x 10^-6C)(1,4 x 10^-6C) / 1,7mm^2+(9*10^9 Nm^2/C^2)(1,6 x 10^-6C)(7,2 x 10^-6C) / 3,4mm^2

 

[Kofyebs]

Yes! I understand now. Thanks once again. you've saved me. ;)