This isnt a hw question, I just thought of it but don't know how to model the situation Given a pulley system like this http://img101.imageshack.us/img101/2106/pulleys.png [Broken] suppose the string is massless and the pulleys are massless and frictionless. say m2 is greater than m1, each having 2*tension force pulling up, they will have different accelerations since f=ma? But since the length of the string is conserved, shouldnt they both be moving up at the same speed, hence their acceleration should be the same? I am very confused. Help please!