Flooter,
DnD is not a physics simulator, and was never supposed to be. You are overcomplicating things.
I wasn't trying to suggest how shoving should be done, I was trying to surmise how it actually works in the game engine. I'll try to explain more clearly.
The shove UI shows an arc behind the target. Where that arc meets the ground is where the target lands if the shove is successful. It's the same arc whether or not you're next to a ledge, but it's cut off at a different point. My guess is that arc is calibrated to work when you're not next to a ledge.
With non-ledge shoves, the game gives the target enough momentum to lift it above the floor and drop it five feet away and everything looks good. With ledge shoves, the game gives the target the same momentum as before, except when the target is dropped, it retains all that momentum and continues forward as well as down.
That, in my assement of how the game works, is why ledge shoves look so goofy.
