Question

Two identical cork balls, each of mass m, are hung
from a common point by two insulating threads of negligible
mass, each of length L = 50.0 cm. Each ball has a charge
Q = - 0.2 C distributed uniformly over its volume. The balls
repel each other and assume an equilibrium position as shown. ( 30° from the center line.)

a) Draw a free-body force diagram for one of the two masses.

b) Write down ∑F_x = ma_x and ∑F_y = ma_y for the mass m.

c) Solve the equations in part b) to determine the tension, T, in the threads, and the mass m.
  

(Careful with conversion from given units to SI units: prefix “centi” means 10^-2 and prefix “micro” means 10^-6. Approximate values for gravitational acceleration and Coulomb’s constant are g = 10 m/s² and k_e = 9 x 10⁹ Nm²/C², respectively.)

Answer 1