1. The problem statement, all variables and given/known data An oil drop with a mass of 7.20*10^-16kg moves upward at a constant speed of 2.50 m/s between two horizontal, parallel plates. If the electric field strength between these plates is 2.20*10^4 V/m, what is the magnitude of the charge on the oil drop? 2. Relevant equations F = ma Fg = mg Fe = qE E = V/d 3. The attempt at a solution F = ma F = m(0) Fnet = 0 Fnet = Fe - Fg Fg = Fe q = mg/E q = 3.2*10^-19C My problem is conceptual. I don't really understand how the particle can have a constant velocity and a net Force of zero upon it. How did the particle accelerate from stationary to it's current velocity?