I'm trying to remember enough of my college physics to form a cohesive argument, and failing. Still, I'm pretty sure that what's happening there is similar to what happens with oscillation. The guy's lift from the first curve is so great that he comes down at a point in the next curve that amplifies the next lift, and eventually it reaches that point where his body is basically out of control. If he were much lighter or heavier, this wouldn't happen. Just as wind blowing at just right velocity can cause a bridge to tear itself apart, someone with just the right (or wrong) mass will tend to do this on that slide.
I still consider it an engineering failure, because it's possible to determine the mass at which this will happen, and if it's well within normal, then you don't build the slide. You come up with a design where this won't happen. Most kids will be fine, most adults will be fine, but if this can happen to someone of not-unusual mass, it's a safety hazard.
Topic: The GIF Thread, v. Do Over (Read 319211 times)
