Teleportation is a fun and tricky ability in combat. It's doubly enjoyable when you can twist it in ways that make the DM scratch his head.
Question: Is momentum conserved when teleporting?
This is an old chestnut in science fiction. The classic example is a person--let's call him Bob--at the North Pole who teleports to Cancun. According to the first law of thermodynamics, Bob lands on the beach in his Speedo to suddenly find the Earth rotating beneath his feet at more than 900 mph. It would be very convenient for Bob if teleporting somehow (magically?) matched his post-teleport velocity to post-teleport conditions.
There are two possibilities worth considering here. (There are others, but they're weird variants that open the game to even worse abuse than where we're going.)
1: Momentum is conserved. Whatever velocity you had before the teleport, you still have after the teleport.
2: Momentum is not conserved. Your velocity becomes zero relative to your destination.
Let's look at a classic D&D example: Bob steps off a 200-foot cliff and plunges toward the rocks below. "What are you doing, Bob," everyone cries. "You'll be smashed to pulp!"
"Relax," says Bob, "I've got an angle. When I have 10 feet to go, I'll teleport down to the ground and take no damage. Boo-yah!"
And the DM scratches his head ...
The first instinct of most DMs in this situation, I think, would be to rule that this trick doesn't work. It's counter-intuitive and feels like it's against the spirit of the rules, so Bob shouldn't get away with it. But that can have unwanted consequences in other situations ...
... like this one: Bob is surrounded by orcs. His sidekick, Red, is on a flying carpet and approaching fast. Red says, "I'm going to swoop low over Bob so he can teleport up onto the carpet, but I'm not stopping, because that would make me an easy target for the orc archers." According to plan, Bob teleports from inside the ring of orcs onto the flying carpet. Unfortunately for Bob, the carpet is streaking by at top speed and Bob was standing still. The DM is thrilled by the drama of the moment and wants this heroic ploy to succeed, but he has already ruled that momentum is conserved. Caught in his own trap, the DM rules that Bob tumbles off the back of the speeding carpet and the orcs chop him into chum.
Absurd examples? Extreme perhaps, but hardly absurd in the context of D&D.
So which is it? If you were the DM, how would you rule in those two cases?
Next time: The Case of the Teleporting Rope.