Re: If I roll a marble down a ramp and of the edge of a bench or something why does .
This could be attributed to a few things.
The two marbles surely do not have the exact same surface, the smaller marble may have a slightly rougher surface, resulting in more frictional contact between the two surfaces
Obviously the heavier marble has a larger surface area, this would also mean that there is more air resistance upwards, meaning a lower acceleration downwards due to the net force acting on the marble.
If the larger marble also has a greater mass per unit area, it could punch through the air horizontally much more efficiently also.
The two marbles may have different drag co-efficients, a rough sphere has a drag co-efficient around 4 times that of a smooth sphere
Quite a few different things to think about