[Nukapei]

The problem is that a lot of those instances are in the movies and not the books. For example, Aragorn has no problems with "dying" on the way to Helm's Deep, Leggy never "surfs" down a flight of stairs, Arwen wasn't even near the fords when the "horse waters" came (it was just Frodo, and he was on the far bank), etc. The rest is pure physics!

As for your sister trying out the "surfing" stunt . . . that's kind of unfair to blame the movies for that. That's like saying no movie should have any stunt because people might want to copy them. People just need to have the common sense to understand that that is a movie, this is real life. Yeah, surfing down a flight of stairs isn't realistic, but neither is Elves doing it!