Problem: Two foil balls are connected by a rod and suspended from a string. The connecting rod is mass less and insulated. Each foil ball can be treated as a point mass and has a mass of 10g. The distance between the two balls is 5cm. The rod and balls are suspended between two foil plates creating an electric field of 8000 N/C. Each ball carries a charge of 4 x 10-10 C. When the dipole is perpendicular to the field, it is in static equilibrium.
Part A: What is the magnitude of the external torque that the suspending string places on the dipole?
Please show all work and steps for above problem.