Hanging from threads are two charged balls made of pith (a very light, spongy material that comes from inside the stems of certain plants). The balls each have a mass of 0.100 g and a charge of the same magnitude q and are attracted toward each other, as shown in the figure below. (Take θ = 18.9° and r = 1.82 cm.)
Question: What is the magnitude of the electric force?
F = k (q x q/r^2)
Please Help. I could not figure out how to solve with out q.