Magnitude and direction of the net force on charge -3Q and charge 4Q

[balletgirl]

Homework Statement

Four charges are located at the corners of a square as shown below. Calculate the magnitude and direction of the net force on charge -3Q and charge 4Q.

(sorry don't have picture, but it is of a square with corners -Q, 2Q, -3Q, and 4Q clockwise).

Homework Equations

F= K(q1)(q2)/r^2

K= 8.99x10^9

The Attempt at a Solution

I don't understand how to start with the information I've been given, it seems like its not enough.

 

[tiny-tim]

Hi balletgirl!

Start with the charge of -3Q.

Draw the three vectors through it representing the forces from the other three charges.

Then add those three vectors by adding their components …

what do you get? ​