Detecting if a part is falling?

I've created a system that throws rocks and other objects down a hole into a room, and I was making a thing that does the damage, and I thought, "It's too easy to just have a set damage for each object", so I started making my damage multiplying judging by the object's mass, material, and downward velocity.

That worked, but not the best, because they still do damage even once they hit the ground, and even though I could make the damage just do it to any part it touches, and only does damage once, this brings up the issue of if they hit each other, they stop doing damage, and also if they hit the part spawning them in, then don't do damage.

I'd rather not use any of the ways I've found so far because they practically all use humanoids, and I happen to be spawning in about 100-250 mesh parts each and every time this gets activated, so that would shred any frame rate on most devices.

So, in short: Is there a way to easily detect if a part is falling?