1. The problem statement, all variables and given/known data 2. Relevant equations The picture is all we know about the entire system, we need to derive an expression for the acceleration of ramp M. There is no friction anywhere. The ramp is free to move on the surface beneath it. 3. The attempt at a solution I drew the free body diagrams as such: M: Mg pointing straight down, N_M pointing straight up, force of m on M pointing opposite of m. m: mg pointing straight down, N_m pointing at an angle θ and 90 degrees to the incline. System: (M+m)g pointing straight down, N_M+m pointing straight up. I'm not sure if that's right and if it is, I don't know what to do next.