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Old 08-23-2012, 09:34 PM   #62
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Join Date: Oct 2005
Posts: 34,461

Originally Posted by toly View Post
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.
sureshs is offline   Reply With Quote