1. The problem statement, all variables and given/known data Two identical spheres with mass m are hung from silk thread with length L. Each sphere has the same charge, so q1=q2=q. The radius of each sphere is very small compared to the distance between the two spheres, so they may be treated as point charges. Show that if the angle θ is small, the equilibrium separation d between the spheres is d=(q2L/2πε0mg)1/3 (Hint: If θ is small, tanθ=sinθ) 2. Relevant equations F=ma=Eq The masses are hung from thread connected at the same point so that it looks pendulum-esque and possible use of triangles. 3. The attempt at a solution Well I started off with this equation F=mg=Eq then used symmetry mg=2Exq mg=2E sin(θ) q mg=2q/(4πε0) (1/(1/2d)2) sin(θ) q and sin(θ)=r/L so I got mg=2q2/(4πε0) (4/d2) (r/L) mg=2q2/(πε0d2) (d/2L) mg=q2/(πε0dL) and d is... d=q2/(πε0Lmg) I'm thinking that I would get the correct d if I lose the 2 from the electric field symmetry and switch the sin(θ) values (L/r instead of r/L), then I would get a d3 and an L in the numerator and it would work fine hahaha. Thanks for help!