When you cast the spell Reverse Gravity, creatures start falling upwards into the air. Assuming that there is nothing in their way the spell must somehow halt their momentum when they reach the top of it, as the spell says "If an object or creature reaches the top of the area without striking anything, it remains there, oscillating slightly, for the duration." If it didn’t halt their momentum somehow, they would fall up into normal gravity for another 100 feet or so, and then almost all the way back to the ground (with real world physics anyway; air resistance would be the only thing that slowed them down, and that would only remove about 5 feet worth of momentum per 100ft fall- I did the math).
Because of this I’m assuming that the spell stops momentum when the creatures hit the top of the spell area somehow.
But what happens if you drop concentration on the spell while they are falling upwards? The condition "If an object or creature reaches the top of the area without striking anything" no longer applies, as the spell isn’t in effect anymore. Physics tells us that the creature falling upwards 100 feet in a reversed gravity field would then have enough momentum to ‘fly’ another 100 feet upwards beyond that until slowing to a stop and falling back down (discounting air resistance). So lets say you dropped concentration just before they reached the top of the spell area; would they then fly up to a height of 200ft off the ground before then falling to the ground for 20d6 damage?
I know you can drop concentration as a free action anytime, but this spell doesn’t seem to indicate how it works exactly regarding the momentum gathered while falling upwards. I’m wondering if the above interpretation is reasonable.