That's interesting, but I would say that the result of this experiment has no connection to the object size. On the other hand the experiment itself does - the experiment tests the influence of the object size on the velocity.
You didn't mention whether that planet has an atmosphere, but, if it does, then size matters less than shape and density. Is it a large flat rock, or a small aerodynamically shaped rock? Is it a rock diamond or a sedimentary rock?
Here, they say גודל החפץ but in another sample sentence they use the phrase מסה של החפץ. Why do these two, which clearly are similar in structure and even meaning, have two different forms? Is either correct in either case, or is one always smichut and the other not?