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Whipcracking is the act of producing a cracking sound through the use of a whip. Used during livestock driving and horse riding, it has also become an art. A rhythmic whipcracking belongs to the traditional culture among various Germanic peoples of Bavaria (''Goaßlschnalzen''), various Alpine areas (''Aperschnalzen''), Austria, and Hungary (Ostorozás). Today it is a performing art, a part of rodeo show in United States, a competitive sport in Australia and increasingly popular in the United Kingdom, where it crosses boundaries of sport, hobby and performance. ==Physics== The crack a whip makes is produced when a section of the whip moves faster than the speed of sound creating a small sonic boom. The creation of the sonic boom was confirmed in 1958 〔B. Bernstein, D. A. Hall, and H. M. Trent. "On the dynamics of a bull whip", ''Journal of the Acoustic Society of America'' 30: 1112-1115 (1958).〕 by analyzing the high-speed shadow photography taken in 1927.〔American Physical Society (2002) ''(Whip Cracking Mystery Explained ),'' 26 May 2002〕〔 Recently, an additional, purely geometrical factor was recognized: the tip of the whip moves twice as fast at the loop of the whip, just like the top of a car's wheel moves twice as fast as the car itself.〔〔Alain Goriely and Tyler McMillen, "(Shape of a Cracking Whip )" Phys. Rev. Lett. 88, 244-301, June 2002 〕 A common explanation is to derive the behavior from the conservation of energy law. However it was noted that the energy is also conserved when the crack sizzles, therefore derivations from purely conservation laws, including conservation of momentum and some others are insufficient.〔 In 1997 the ''Discover Magazine'' reported about the possibility of the "whipcracking" effect millions of years ago. As part of the joint computer scientists' and paleontologists' research into the motion of dinosaurs, Nathan Myhrvold, a chief technology officer from Microsoft, carried out a computer simulation of an apatosaurus, which has a very long, tapering tail resembling a whip. Basing on the reasoning described above, Myhrvold concluded that sauropods were capable of producing a crack comparable to the sound of a cannon.〔("Dinosaur in Motion" ), ''Discover'' November 1997 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Whipcracking」の詳細全文を読む スポンサード リンク
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