Coulomb's Law: Two Small Insulating Spheres Are Attached to Silk

Multiple Choice

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 μC 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 = 1/4πε₀ = 8.99 × 10⁹ N ∙ m²/C²) The tension in the lower thread is closest to

A) 1.2 N.
B) 1.4 N.
C) 1.6 N.
D) 1.8 N.
E) 2.0 N.