1. The problem statement, all variables and given/known data The potential between the cathode and the screen of a computer is 12kV. What is the speed of an electron when it reaches the screen if it starts at rest at the cathode? 3. The attempt at a solution First I found that the force that acts on the electron is 1.922E-15 N. I can then find the acceleration, but I need the distance between the cathode and the screen to find the speed. Can I use energy conservation? Probably. Gravitational forces can be ignored. (1/2)mv^2 = Epot But what is the the expression for potential energy? Not mgh. Can I simply replace m with charge, g with E and h with the potential? 1/2)mv^2 = eEU ?