[RPG] Do Teleportation spells transfer kinetic energy

A spell is resolved - and the target is determined - when the spell comes into effect, not when spellcasting is "starting".

So in the example the sorcerer could still cast the spell, just another target would be determined if they are no longer aware of where the wizard is. The only way to stop the spell being cast (Spell resistance, saving throws, etc are another matter) would be to counterspell or disrupt (Concentration checks) the spell itself - removing the (intended) target before the spell is complete simply means that the caster (the sorcerer in this case) is free to choose a new target.

Ie. Even though the sorcerer had taunted the wizard the spell target hadn't yet been determined.

This is usually most relevant when a spell takes more than a simple action to cast (such as sleep, a one round to cast spell) but when reactionary effects get in the way spellcasters can still choose their target if their original one vanishes before their spell can take effect.

It's detailed in the Casting Time section of the Magic rules of Pathfinder, but the most important line of it is:

You make all pertinent decisions about a spell (range, target, area, effect, version, and so forth) when the spell comes into effect.

So, in the fraction of a moment where the wizard teleports away the spell's effect has not been determined - the wizard hasn't made a saving throw. So the sorcerer is still free to target anyone else they want. If there are no relevant targets of course (say, charm animal and all the animals vanish into the ether on a joyride) then obviously the spell will fail through lack of targets.

The rules for falling do not address timing or actions at all. They only specify damage taken.

However, the general rules for the game are that things are atomic—you do one action, you do another, and you cannot mix them or interleave them. There are exceptions—Spring Attack, 5-foot-steps, etc.—but they are exceptional. Without some explicit exception, I would default to assuming that you must finish falling—more on what that means in a bit—before you can do something else.

Therefore, if, at any point in time, there is no longer ground beneath you, you fall immediately. You are not in control and cannot act normally. If it was your turn, that pauses until the fall completes—details still forthcoming—and it is effectively no longer your turn. This is similar to the situation with attacks of opportunity, which interrupt an action or turn to allow a different creature to act (and attack).

Some actions, principally immediate actions, can be taken out-of-turn and therefore always can occur during a fall. Feather fall is even specifically designed to be used just as you begin to fall. Likewise, if you have some relevant ability to act in the middle of movement—maybe Spring Attack if this was an intentional jump off a cliff perhaps—I would expect most DMs to allow it to apply, though the rules are murky about that. You could also presumably ready an action to take place after you’ve fallen a certain distance or when you’re a certain distance above the ground, but you would have to ready the action prior to falling in my estimation.

Dungeon Master’s Guide II specifies that on the first round of a fall from a very great height, a character falls at most 670 ft. So if you are higher than that, the fall “completes” for the turn, and you act after that.

Thereafter, each round is another 1,150 ft. Round-by-round durations in 3.5e are somewhat odd, but very clear: anything that is supposed to occur X rounds after some point, occurs X rounds later when you reach that same initiative count. Initiative does not change during a given turn, so your fall began on the relevant initiative count, and you continue to fall as soon as the initiative reaches that point again—that is, before any creature acts on that initiative count.

These numbers (670 ft and 1,150 ft) are a fair bit larger than dlras2 had calculated using the relevant real-world physics,¹ but then maybe the acceleration due to gravity is larger in D&D than on Earth.

There are no restrictions present in the rules on how you may spend your actions if your turn comes up in the middle of free-fall (that is, after dropping 670 ft in the first round, or after dropping 1,150 ft on any round thereafter). Presumably, if you only have a land-based movement speed, you would not be able to actually move, but you would get a move action, as well as swift and standard actions, as usual. Because of the abstractions present in the rules, this means that for shorter falls, if you fall during your own move action you can land and still make your Standard action afterwards. In theory, maybe some or all of that is actually going on during the fall but the game does not model that.

Personally, if this was any thing like a major part of a campaign I was running, I would houserule some way to move as a move action while in free fall—even without any kind of equipment you can aim yourself in a long fall, though I’d have to do some research on how much.

1. _{See the comments for dlras2’s calculation. Using real-world physics and a lot of estimation, and assuming you take 20d6 damage, i.e. 200 ft., to be the point at which you hit terminal velocity, you would move 470 ft. in the first round and 660 ft. per round thereafter.}