Newton's Pendulum, Gangnam Style

It's been ten years, so you ought to be able to handle the song by now. And you'll be glad you did, as five balls demonstrate conservation of momentum in a Newton's cradle. The movements become more sophisticated as the song progresses, and you can't help but grin watching this simple desk toy boogie down. The rhythm and editing is just right for the song, and if you have a Newton's cradle, you'll go try all the funky moves you didn't know it could do.  (via Metafilter)