1. The problem statement, all variables and given/known data A proton of mass 1.67 * 10^-27 kg moves from a location where V1 = 75 V to a spot where Vf = -20V. a) Calculate the change in the protons kinetic energy b) Replace the proton with an electron, determine its change in kinetic energy 2. Relevant equations 3. The attempt at a solution The kinetic energy does not matter to me, but the sign does; so for a) The way I see it, the diagram looks like this: ++++++++++++++++++ (75 V) A B ----------------------- (- 20V) The proton moves from A to B, so it loses potential energy and it converts to kinetic energy. Kinetic energy is Positive, and this is correct! B is where the confusion begins :( b) This is how I see the diagram in my head ++++++++++++++++++ (-20 V) B A ----------------------- (75 V) The electron moves from A to B. It's potential energy decreases and converts to kinetic energy! What? I got the same answer as A, positive kinetic energy! But the answer is negative kinetic energy! The only way to explain this is that for b my diagram was indeed wrong, meaning it should be 75 V at the positive terminal and -20 V at the negative terminal! But this goes against what my teacher taught me. Hopefully someone can clear up my confusion. Thank you for your time!