1. The problem statement, all variables and given/known data A triangle shaped moving block of mass M2 is pushed by force F , a block of mass M1 is on the other block, a)what should be the F force so that the block will be in rest relative to M2? b)what should be the Acceleration of M1 so that the block M2 will move up on the block M1 in an acceleration of A2? c)what should be the Acceleration of M1 so that the block M2 will move down on the block M1 in an acceleration of A2? 2. Relevant equations F=ma... etc equivalence principle can help here as well... 3. The attempt at a solution K, a) is done for me, easy, solved it in two ways 1)equivalence principle(elegant way), 2)using D'Alembert's principle and some newton's laws. now b) ffs!!!!! I hate it, nothing that I do works!!! nothing that I could think off,damnit! the main thing that bothers me is that they don;t have the same acceleration now! So If some 1 can point me in the right direction/hints or W\E that will help me finish this problem. this is an epic sketch> I will add a normal one if it is needed. | \ | \ | \M2 |M1\ pushed to the right-------->>> so thank You!