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 ? = 20.1° and r = 1.87 cm.)
(a) What is the magnitude of the electric force?
(b) What is the magnitude of q?
(c) How many electrons have been transferred to or from each ball?