see this image https://docs.google.com/leaf?id=0B5...AtMTZmMDU5ZGIwOGQx&hl=en_GB&authkey=CL3RqN4O" something about question:=> a block M1 placed over M2 Nd M2 placed on the earth.A constant force F is applied in upward direction. You have to tell about the motion of M1 and M2 in condition as given below pulleys are frictionless and only friction is in between M1 and M2. first case In first case friction is zero between both blocks so will block M1 and M2 is zero. second case friction between M1 and M2 is very large. tell me about acceleration about the bodies in both cases if you think more variable required to answer then introduce them. My mind says that there will acceleration in Block M2 will something in second case but sometimes i think that acceleration of M2 will zero in both cases. I say there will acceleration in block M2 zero because force is in upward direction(this logic seeming wrong) but i think there will acceleration in block M2 because a force will act due to tension(string between M1 and pulley. Guys put your thoughts here i will thankful for you.