1. http://www.prep101.com/MCAT/102MCATPhysicsAnswers.pdf number 17 3. Here is my attempt: First I figure I have to find the deceleration of the particle. So I plugged it into the v(final)^2= v(initial)^2 + 2ax. I solved for a and got a and got -240000. I don't know if I am correct here but I plugged the accel and mass into F = ma and got a force of 1.608*10^-21N I also tried substuting equations such as = F = Eq to ma = Eq but I still haven't gotten an answer along the lines of the choices. Please help me. Thanks in advance.