1. The problem statement, all variables and given/known data "Two identical beads each have a mass m and charge q. When placed in a hemispherical bowl of radius R with frictionless, nonconducting walls, the beads move, and at equilibrium they are a distance R apart. Determine the charge on each bead. (Use k_e for ke, g for the acceleration due to gravity, m, and R as necessary.)" Here's a picture: http://img3.imageshack.us/i/p2368.gif 2. Relevant equations Relevant equations include Coulomb's Law, and other elementary physics equations. F = Ke * (q1) * (q2) / (distance)2 Where Ke = 8.9 x 109 3. The attempt at a solution So what I've gotten so far is this: Using the left-most ball as a model, there's a force in the negative x direction from the ball on the right. That force is exactly F = -Ke * (qe)2/R2 Now there's a y component of the normal force from the hemisphere given by: mgsin(x) = N So, I also figured that the normal and the gravitational forces should each have an x component and that it should be equal and opposite of the force from the charge on the right: Ncos(x) = Force from the charge So here's what I did from there: Ncos(x) = Ke * (qe)2/R2 Nsin(x) = mg tan(x) = mg / ( Ke * (qe)2/R2 ) R2 / tan(x)mg = Ke * (qe)2 R2 / tan(x)mg * Ke = (qe)2 And ended up with: qe = sqrt ( R2 / tan(x)mg * Ke ) Which is incorrect.