I was thinking about this situation with a friend of mine, and we had opposing views:
Suppose you have a frictionless table with mass M resting on top. You attach a chain to the mass M, a chain with another mass already attached to the other side. You let this other mass hang from one end of the frictionless table, while making sure mass M is stationary, holding it down with your hands. As soon as you stop exerting a force on mass M, letting it fall under the influence of the hanging mass, the hanging mass accelerates downwards with an acceleration of g.
The chain is very heavy, and its weight is not negligible.
How would the mass M accelerate?
1) It makes sense to me that the mass M would accelerate at a constant acceleration of g - although the weight of the chain is not negligible, the mass of an object doesn't play a role in its acceleration. As the hanging mass would be in free fall, the mass M, because rested upon a frictionless surface, would also be, in a sense, in free fall.
2) My friend thinks that as the hanging mass falls, the force downwards (the gravitational force) would increase: F = ma, where although a is constant, because the mass of the chain is not negligible, the total mass is increasing as more of the chain is pulled by the hanging mass in free fall, and therefore the mass M would be pulled with a greater force, leading to an increasing acceleration against time.
Which seems to be more accurate, and why?