1. The problem statement, all variables and given/known data here: http://img144.imageshack.us/img144/7518/26700576ok1.gif 2. Relevant equations 3. The attempt at a solution well, I tried to solve the motion equation from the inside table. I think there should be a d'elambertian force to the left, and friction force to the right, so: Fd - miu*N = m1*a . Now, Im not sure about the Normal force- need it be N=m1+m2, or just m1 (I think it's the first option). Then my main problem - about the d'elambertian force: Is the Fd equal to the external frame's F, or are the accelerations equal, and the forces need to be calculated via the acceleration and masses? And finally: when I try to calculate on the external frame (the cart): need the motion equation be equaled to just Ma, or all the masses, ie (m1+m2+M)a ? Thanks in advance..