Originally Posted by toly
1. In first case momentum before collision was mv. After collision momentum is
(M+m)(mv/(m+M))=mv. So, mv=mv and everything is fine with low of conservation of momentum.
2. In second case momentum before collision was Mv. After collision momentum is
(M+m)(Mv/(m+M))=Mv. Again everything is fine and Mv=Mv.
Circular argument since I derived the speed using the conservation of momentum and you used that expression.
I am asking why the system behavior is different in the two cases. I know I am wrong, but I want to know why.