How do I find electric force on a charge without its coordinates?

[NINHARDCOREFAN]

https://hw.utexas.edu/tmp/Muddam1/1077041275Xuj.pdf

I'm stuck on fourteen. Without the charge's coordinates how can I calculate the electric force on the charge?

 

[Doc Al]

Originally posted by NINHARDCOREFAN
Without the charge's coordinates how can I calculate the electric force on the charge?

The charge is at the origin, coordinates 0,0. (Hint: Problem #14 uses the results of prob #12.)

 

[NINHARDCOREFAN]

Oops.

Didn't take notice of the word "origin". Anyway, you don't need to the answers from #12 because F= k*q1*q2/r^2 and you find force of the charges on the origin charge and take the magnitude of it.