1. The problem statement, all variables and given/known data 2. The attempt at a solution I have the solution, but it's pretty confusing so I want to see if anyone else can walk me through step by step. The first step is pretty clear...You have to find the acceleration that the proton will experience as it moves towards the upper (positive) plate. F = ma a = F/m F = qE a = (qE)/m a = -eE/m From there what do you do? Set it up in a kinematics equation? How does the surface charge density come into play?