. Farm implements, and the principles of their construction and use; an elementary and familiar treatise on mechanics, and on natural philosophy generally, as applied to the ordinary practices of agriculture ... ight, and the pow-er of the instrument will therefore be doubled ; if twiceas far, it will be tripled, and so on, as shown in the an-nexed figures. The same mode of reasoning will ex-plain precisely to what extent the force is diminishedin levers of the third kind. These rules will show in what manner a load borneon a pole is to be placed between two persons carryingit. If equidistant
. Farm implements, and the principles of their construction and use; an elementary and familiar treatise on mechanics, and on natural philosophy generally, as applied to the ordinary practices of agriculture ... ight, and the pow-er of the instrument will therefore be doubled ; if twiceas far, it will be tripled, and so on, as shown in the an-nexed figures. The same mode of reasoning will ex-plain precisely to what extent the force is diminishedin levers of the third kind. These rules will show in what manner a load borneon a pole is to be placed between two persons carryingit. If equidistant between them, each will sustain alike portion. If the load be twice as near to one as tothe other, the shorter end will receive double the weightof the longer. For the same reason, when three horsesare worked abreast, the two horses placed togethershould have only half the length of arm of the mainwhipple-tree as the single horse, Fig. 48. The farmerwho has a team of two horses unlike in strength, maythus easily know how to adjust the arms of the whip-ple-tree so as to correspond with the strength of , for instance, one of the horses possesses a strength ESTIMATING THE POWER OF LEVERS. Fig. 48. 69. as much greater than the other as four is to three,then the weaker horse should be attached to the armof the whipple-tree made as much longer than the oth-er arm as four is to three. In all the preceding estimates, the influence of theweight of the lever has not been taken into consider-ation. In a lever of the first kind, if the thickness ofthe two arms he so adjusted that it will remain bal-anced on the fulcrum, its weight will have no othereffect than to increase the pressure on the fulcrum;but if it be of equal size throughout, its longer arm,being the heaviest, will add to its power. The amountthus added will be equal to the excess in the weightof this arm, applied so far along as the centre of grav-ity of this excess. If, for example, a piece of scantling twelve feet lon
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Keywords: ., bookcentury1800, bookdecade1850, bookpublishernewyo, bookyear1854
