I stumbled across this while watching the Walter Lewin MIT Physics lectures. Fortunately, it also appears as a stand alone video (isn't YouTube wonderful?) so you don't have to watch an hour on kinetic friction coefficients. But you could if you wanted to. In magic there is a dramatic device known as the "kicker ending", which involves adding on an additional incongruous climax following the apparent ending to a trick. For example, you remove a pack of cards from its box, perform a brief trick and when you try to return the cards to the box, you discover that it is now filled with a block of ice. Essentially, you turn your magic show into an episode of Family Guy.
Magicians will sit up in bars and coffee shops for ridiculous amounts of time debating the merits of this type of dramatic structure. But I never thought I would see it used in a physics demonstration. Just trust me when I say, you will not see this ending coming:
