A block of mass M1 sits on a table, with no friction, anda block of mass M2 is s

Question

A block of mass M1 sits on a table, with no friction, anda block of mass M2 is suspended by a cord of negligible mass over africtionless pulley. At t=0s the blocks are at rest, and thehanging mass starts descend. Student X says: "The hanging mass is pulling down on therope, so the tension in the rope is (M2)g. That's the forceon the block on the table, so that block's acceleration isa=F/m=(M2)g/M1." Student Y says: "That can't be right, because if M2 is biggerthan M1, then M1 will have an acceleration bigger than g!"
I am confused about the overall problem. Just don'tunderstand at all. A block of mass M1 sits on a table, with no friction, anda block of mass M2 is suspended by a cord of negligible mass over africtionless pulley. At t=0s the blocks are at rest, and thehanging mass starts descend. Student X says: "The hanging mass is pulling down on therope, so the tension in the rope is (M2)g. That's the forceon the block on the table, so that block's acceleration isa=F/m=(M2)g/M1." Student Y says: "That can't be right, because if M2 is biggerthan M1, then M1 will have an acceleration bigger than g!"

Explanation / Answer

the tension in the rope is not equal to mg of the hanging massbecause the system is accelerating. If it were notaccelerating that would be the case. The tension in the ropeis going to come from F=ma. On the hanging block the twoforces on it are gravity and the tension so T-mg=ma. You alsoknow that the two blocks are going to move at the same speed so thema of the block on the table = ma of the hanging block F=ma on theresting block is T=ma. So you can set your equation equl toeachother and solve for the acceleration of the blocks because theyare the same.
Hope that hleps

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