Three charges q, uniform circular motion

[colmes]

Homework Statement

Two spheres have a charge of q a stationary sphere between them has a charge of -q. The 2 positive spheres move like conical pendulums at a constant velocity of 12.0m/s in uniform circular motion. What is the magnitude of charge q?

Homework Equations

Electric Force = kq1q2/(r^2)
(mv^2)/r = Centripetal Force
Fg = mg

The Attempt at a Solution

I did some calculations but found difficulty because I don't know that mass of the two side spheres were.

 

[lightgrav]

I would call them 1kg, to get a solution ; later you change them to ½kg, or "m"
(the charge will or course be different; this will get you the dependence on m)