SCIENCE FILE : I Didn’t Know That . . .

Q: Does the tip of a bullwhip really exceed the speed of sound?

A: Yes, according to physicist Collier Smith of the National Institute of Standards and Technology. The whip has to be moved so that a U-shaped loop is formed near the handle, where the whip is thickest and heaviest. As the loop travels down the length of the whip into progressively thinner sections, it moves increasingly faster, just as a small ocean wave becomes higher as the water becomes shallower. By the time the loop reaches the end of the whip, the tip is accelerated past the speed of sound, creating a tiny shock wave that we hear as a “crack.”