Here's a little physics in action to bring in the new year. http://www.smh.com.au/news/world/robbie-maddison-completes-vegas-jump/2009/01/01/1230681649061.html His runway speed was 54 mph. About 24 m/s. Figuring that V² = 2gh that translates to about 97.5 feet of potential energy. The Vegas Arc de T is 96 feet high. Physics pays dividends. The descent from the roof however was a bit more harrowing. He apparently hit the ramp a little far down and experienced slightly more deceleration over a shorter distance than he would have wanted. That would seem to have resulted in a broken hand. Ouch. Kids don't try this at home.