1. The problem statement, all variables and given/known data Two masses are tied together by a string over a massless pulley so that they can both move vertically. Their masses are 1 kg and 3 kg. What is the acceleration of the 1 kg mass? 2. Relevant equations F=ma W=mg 3. The attempt at a solution I have the 3 kg mass's summation of forces as ma-T. (In my free body diagram, the 3kg mass is the one closest to the pulley.) The 1 kg mass's summation of forces are mg-T. I'm unsure if my diagram is correct and I don't know where to go from here.