1. The problem statement, all variables and given/known data A 2.70-mm-diameter glass sphere has a charge of + 1.10 nC. What speed does an electron need to orbit the sphere 1.50mm above the surface? 2. Relevant equations a = v^2/r -> force = m*v^2/r electrostatic force = K*Q1*Q2/distance^2 therefore: m*v^2/r=K*Q1*Q2/distance^2 3. The attempt at a solution (9.10938291 × 10-31 kg)(v^2)/((2.7*10^-3)/2) = 8.99*10^9*(1.60*10^-19)*(1.1*10^-9)/(1.50*10^3)^2 I get 32282518 m/s which is the incorrect answer. However, I just noticed something. The radius I'm using is half of the sphere, should I be adding the separation distance to the radius as well?