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Sonic Boom

Who says you never learn anything watching television?  Well, I usually do.  And this week I was proven wrong.  I was watching a documentary on my flight over to Hong Kong yesterday on whips – as in bullwhips.  Apparently, a whip “cracks” not because the leather snaps against itself, but because the end of the whip breaks the sound barrier.

I dug around to see if this was actually, conceivably true.  Indeed, bullwhips are designed so that the handles are heavy and the “cracker” at the end of the whip is very light.  The initial wave of energy sent through the whip by swinging the handle remains constant, while the mass of the whip declines.  The only way to preserve kinetic energy is for the whip to travel faster per the formula E  = mv^2/2.  You don’t actually need the cracker to break the sound barrier; it will just make the sound louder.  You can actually break the sound barrier by  just twisting a wet towel and cracking it against one of your friends.  Now you know why it stings so bad.

For the sake of improving my technical prowess, I embedded of a video with a record-holder in whipping.  I wonder if anyone has ever asked him if he should wear earplugs while whipping.  Or, since he says he is looking for a career change, if he has considered looking into pornography.

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