Scientific amusements . Fig. 38,—Kxperiment in Equilibrium. will be evident that the least touch will bring it to theground. On the plank thus balanced place a newspapersheet ; and then if you strike the portion of the plankwhich extends beyond the table you will be surprised tofind that the plank will resist the blow absolutely, as if ithad been nailed to the table. If you strike hard youwill perhaps hurt your hand or break the plank, but youwill not raise the sheet of newspaper which holds quick compression of the air which is exercised ona considerable surface is sufficient to explai
Scientific amusements . Fig. 38,—Kxperiment in Equilibrium. will be evident that the least touch will bring it to theground. On the plank thus balanced place a newspapersheet ; and then if you strike the portion of the plankwhich extends beyond the table you will be surprised tofind that the plank will resist the blow absolutely, as if ithad been nailed to the table. If you strike hard youwill perhaps hurt your hand or break the plank, but youwill not raise the sheet of newspaper which holds quick compression of the air which is exercised ona considerable surface is sufficient to explain thisphenomenon (Fig. 38),: resistance of the air. 49 Resistance of the australian boomerang. Everyone has heard of the Australian boomerang. Itis a weapon formed in the shape of an arc of hard wood,which^ the Aborigines and , inhabitants of Australia throwwith unerring skill at some object—an enemy or the boomerang strikes the object aimed at, it. ?? ~.\ V ^ \ Fig. 39.—The Boonieraiij. \ returns to the hand which launched it. One may quicklylearn to throw_this weiapon after a few trials. Fifteen years ago M. Marcy, of the Paris Institute,published an interesting paper on this subject in theAeronaut, in which journal were discussed questions relativeto the resistance of the air. The learned professor thenprepared^uncpnsciously—-a little chapter for Scientific 50 DENSITY, HYDROSTATICS, ETC. Amusements, and we will reproduce the gist of hisremarks. A piece of cardboard shaped into a crescent, the cornersof which are rounded off, should be placed on the, tip ofthe finger, or, still better, supported between the nail andthe finger tip, so that the cardboard be inclined at anangle of 43°, or so. Then, with a vigorous flip of thefinger of the right hand at the extremity of the toy, itis impelled into the air with a rotatory motion. Thecardboard crescent then appears as a wheel, and movesin an oblique ascending direction, stop
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Keywords: ., bookcentury1800, bookdecade189, booksubjectscientificrecreations
