Anthony Delongis trained Pfeiffer on how to use the whip- he was (and probably still is) the default go-to guy for Hollywood on instructing actors on how to use that weapon, and a couple others, I believe he's also a talented swordsman.
Or they just had some release mechanism pop off the heads when she whipped near them? Seems like that would be faster and easier than training an actor to whip off 4 in a row during one perfect take.
The tip of a whip goes supersonic, that's why they make a cracking noise. You're seeing a sonic boom and the dust flying off the whip. Whips are almost certainly the first man-made supersonic objects.
Reddit
Digg
Stumble
Facebook