1. The problem statement, all variables and given/known data Three point charges are arranged as shown here: http://puu.sh/ltvxF.png [Broken] a. Find the electric field at point A. (Give as vector, either as i and j or magnitude and direction.) b. Find the potential at point A. c. If an electron is placed at point A and released, what is the magnitude of its final velocity? 2. Relevant equations a. E = (kq)/ r2, Ey = Esin(theta), Ex = Ecos(theta) b. V = (kq) / r c. v = (sqrt(2P/m)) CONSTANTS: k = 8.99 * 109 me = 9.11 * 10-31 kg 3. The attempt at a solution a. For this one, I calculated all the electric fields from each point. For the left negative charge I got E = 8.9 * 104, which I calculated to be Ex = 72000 and Ey = 54000. Because the right negative charge has the same charge, the electric field is the same. So, the electric fields are the same everywhere EXCEPT the x-component because that is negative, so they cancel out. Currently, I have a Ey = 72000. For the positive charge, I got E = -5.6 * 104. (I said it was negative because it is going in the negative-y direction?). So I added all these and got 138400 upwards. My teacher said this was wrong though, where? b. I took this piece by piece. For the left negative charge, I got -4500 ((k * -2.5 * 108)/.05). For the right negative charge, I got the same thing (same charge and distance). For the middle positive charge, I got +2250 ((k * 1 * 10-8)/ .04). Adding these together, I got 6750 V. Which, again, my teacher said was wrong. I looked it up and found no other way to do it. Even in my notes, it says to do it this way. Where did I do it wrong? c. I did not really get where to start. I looked up in some other forums around here (will put a link when i find it) and I kept calculating it to be over the speed of light. After b is fixed, I can probably do this one. So ignore it for now.