7) Coulomb's law: Two small insulating spheres are attached to silk threads and aligned vertically as shown in the figure. These spheres have equal masses of 40 g, and carry charges q1 and q2 of equal magnitude 2.0 C but opposite sign. The spheres are brought into the positions shown in the figure, with a vertical separation of 15 cm between them. Note that you cannot neglect gravity. (k=1/480 = 8.99 x 109 N m/C2) The tension in the lower thread is closest to A. 91 (+) 15 cm 92 B