Physics Help.Coloumb's Law..?

Question

Determine the force on -e (choose any -e in the diagram)
(the shape is square and the edges is 0.1m.)
+e----------(-e)
...l.................l
...l.<-0.1m->l
...l.................l
(-e)---------+e
thanks.p.s. dont mind the dots.

Answer 1

Coloumb's Law says the force between two charged particles is given by: F = k Q1 Q2 / R
http://en.wikipedia.org/wiki/Coulomb's_law

So each charge experiences an interaction with each of the other 3 charges.

Because of linear superposition, the net force on each is just the sum of the three individual forces (treated as vectors)

You have the distances between the charges and the electrostatic constant (it is in the Wikipedia page). If you know the charges, you can compute the force numerically; otherwise you can compute it as a function of e.

("e" is often used to indicate the charge of a single electron:
http://en.wikipedia.org/wiki/Elementary_charge
)