If you've never thought about it, it might seem counterintuitive that on a good slapshot, the stick has to strike the ice before the puck. In this edition of the Youtube science series, Smarter Every Day clearly and concisely explains the physics behind the slapper, and those flex ratings printed on the shaft of every stick.

And, hell, even if you have no use for the science, it's got some great images taken with a high-speed Phantom camera, as well as a puck being crushed in a vise.