4 B + 9 m Figure 2: Two charged spheres, each hanging by a thread. 2. Electroscope Two plastic spheres A and B, both of mass m, hang by threads of length ( from a common point of support (see figure 2). An unknown charge + q is imparted to each sphere. As a result the spheres hang with each thread making an angle 0 to the vertical. Determine q. Give your answer in terms of m, 0, ( and g = acceleration due to gravity. Hint: First draw a free body diagram for sphere A