Take a couple of high school kids, put 'em in a fast car, add a few beers and a driver with a lead foot. Throw in an unexpected obstacle and the rules of physics and what you get is a very abrupt end to a party on wheels.
CCavaliere
You just described my whole senior year, which admittedly ended better than theirs.
It became clear during our experiments that it would take something far more massive than an aluminum mailbox to generate the force necessary to cause the fracture in the victims arm.