[Sabertooth]

You missed the fact that Gandalf caught his sword on the way down. Of course, as any physicist knows, a sword has a higher terminal velocity than a human, or Maia--he should have never caught it.

Terminal velocity is different for wizards plunging to their deaths.

Besides, how did Saruman make Gandalf's staff fall up into his hand in FOTR? Or make Gandalf fall up to the ceiling of Orthanc and land on the roof in the same movie? But then, why couldn't he make Gandalf fall back up to the roof from his eagle-mount during his escape?

Clearly, Middle-Earthian physics are different. Probably magic.

[HairOfTheDog]

Focusing on the believability of catching up the the sword, when we are talking about a fight between a Wizard and a Balrog made of smoke and fire, means the rest of the effects must have been rather believable!