WHY A WHIP CRACKS

Rodney and Otamatea Times, Waitemata and Kaipara Gazette, 23 June 1915, Page 7

WHY A WHIP CRACKS

Why does a whip "crack" ? Probably the coachman most adept at the art whom you discovered would not be able to tell you. And no wonder. For the reason is one that has puzzled some of the greatest authorities on dj'namics.! An explanation was tentatively offered by Professor C. V. Boys in the course of a lecture for juveniles. Briefly, it | has to do with the fact that, owing to j the action of centrifugal and other I forces, the speed at which the whip travels through the air is greater and greater throughout its length, and so great at the end that it comes. upJMfIM velocity of sound. 4j|^^^l The Professor showed wbJ^^^^^^H principles underlying vario^^^^^^^H and, apparently, simple de^^^^^^^H tion, for instance, is onej^^^^^^^^^J est. To the wondermen|^^^^^^^^^J girl audience, Professoj^^^^^^^^^^H "safety matches out^^^^^^^^^^H here," box, and set '^^^^^^^^^| the greatest ease on &l|^^^^^^^^| a piece of mahogany. was a miracle, until ti^^^^^^^^H plained that the friction to make the match get hot^^^^^^^^H er until it flamed. But, dotJHImN the surface on which a "safety^piatcb., is struck must be perfectly smooth, otherwise the roughness will ruh off the substance on the tip. It is friction, too, which prevents a wedge jumping out after the blow that has driven it into; say, a log of wood. Apropos of "impact considered as aj self-adjusting leverage in time," .the boys learnt why, when a cricket ball is hit toG near the end of the bat, the hand is. stung. It is, because the impact/ coming at that particular point, drives the bat up. Just as it did to both ends of.a stick which, when the lecturer broke it by a sharp blow exactly in the middle, flew away in halites, leaving undisturbed ■' two water-filled glasses on which it was resting;; J