Electriccal charges and vectors

[Rave Grrl]

+q    -a-    -q

|            |
a            a
|            |

+2q   -a-  -2q

What are the horizontal and vertical components of the resultant electrostatic force on the charge in the lower left corner of the square if q = 0.9 10-7 C and a = 4.4 cm? (Assume the positive directions are upward and to the right.)


For the horizontal component I got .0013081 N and for the Vertical I got 4.321 N, but neither one is correct.

I found the charge between +2q and -2q, and then I added the charge from +2q to -q times cos(45). That should have given me the horizontal charge but it didn't. What am I doing wrong?

 

[MathStudent]

your answer for the horizontal component is a factor of 2 off (that is my answer is twice the value of your answer), did you account for the 2q?

edit: if show your equations we can see exactly where an error occured

 

[Rave Grrl]

If your answer is .0026162 N that isn't correct either. I don't really know how to show the calculations here though.

 

[MathStudent]

The exact answer I got was .026626077 N, which is assuming that the positive direction is to the right. What does the book say the correct answer is?