No. You can't.

• First off, as meme mentions, speed has no part in this equation. So you're not talkin about a peasant rail gun. You're just talking about a single peasant throwing an item.

• All thrown items use the Improvised Thrown Weapon rules. Those rules state that range gets limited to 20/60. So at maximum you're throwing it 60 feet. Unless you've got wings, a broom or an elevated position then it's not going higher than that.

• But you're not throwing it straight up. You're throwing it at an angle because you're trying to get it to fall on the enemies position. Even if this didnt violate rules as written (two objects cannot occupy the same grid space, vertical space being treated as occupied for the explicit reason of preventing this "tactic") then you're still trying to target a specific point. So you'd be rolling an attack at disadvantage (it's outside normal thrown range of 20 feet) and wouldn't even be able to put it 60 feet above the enemy because you're throwing at an angle to get it to reach that position, not throwing it straight up.

• Everything I've ever seen uses Dex saves for falling objects. So enemy is still using a dex save to evade the attack.

So at most you're doing 50 feet worth of falling damage (5d6) and that's providing you succeed on in a disadvantaged attack roll and the enemy doesn't dex save.