1. The problem statement, all variables and given/known data http://session.masteringphysics.com/problemAsset/1001949/13/knight_Figure_25_69.jpg An electric field 1.00×10^5 N/C causes the ball in the figure to hang at an angle. What is theta? 2. Relevant equations E = F/q F = mg 3. The attempt at a solution The ball isn't accellerating, so it is in equilibrium. Sum of all forces is 0, so the tension force balences gravity + electric field. E = F/q F = Eq F = 100000*(25*0.000001) Fx = 2.5 F = mg F = (0.002)(9.81) Fy = 0.1962 Ft = Sqrt(Fx^2 + Fy^2) Ft = 2.5076870697916038024546202698347 tan(theta) = Opp/Adj tan(theta) = Fx/Fy theta = arctan(2.5 / 0.1962) theta = 85.5126 degrees This answer is wrong. Where is my mistake?