. The Family tutor . echanical advantage as thefirst, will press down the weight end uponthe power end of the third, with a forceequal to 100 pounds. This force of 100pounds, being applied to the power end ofthe third lever, will act upon the same prin-ciples as the others, and raise the Aveightend with a force of 1,000 pounds. In calculating the action of any com-pound system of levers, it does not affect theprinciples of calculation if some of thelevers are of the first kind, and some of anyother. The rule, is to multiply the weighton any lever by its distance from the ful-crum, and multiply
. The Family tutor . echanical advantage as thefirst, will press down the weight end uponthe power end of the third, with a forceequal to 100 pounds. This force of 100pounds, being applied to the power end ofthe third lever, will act upon the same prin-ciples as the others, and raise the Aveightend with a force of 1,000 pounds. In calculating the action of any com-pound system of levers, it does not affect theprinciples of calculation if some of thelevers are of the first kind, and some of anyother. The rule, is to multiply the weighton any lever by its distance from the ful-crum, and multiply the power by its distancefrom the same point; if the products areequal, then the weight and power willbalance each other. If we wish to calcu-late the effect of the system given in , we must multiply the length of thelong arm by the power, and multiply theshort arm by the weight or resistance offered.—W. T. K.] For many of the purposes of science, levers are used to magnify small motionsVOL. v.—NO. Lix. r. Pig. 156. 302 NATURAL PHILOSOPHY. The power causing the motion is applied by a short arm near to the fulcrum of thelever, and the other arm which may be ten, twenty, or more times longer, moves overa graduated scale. The pyrometer is an example of this application. The most accurate means for determining the weight of bodies is by the arranged for this purpose, it passes under the name of The Balance. It is aifever of the first kind with equal arms. Various forms are given to it, and variouscontrivances annexed for the purpose of insuring its lightness, its inflexibility, andthe absolute equality of the lengths of its arms. Fig. 156, represents one of thebest kinds: a a, is the beam ; c is the fulcrum, or centre of motion; d rf, are thescale-pans in which the weights and objects to be weighed are applied ; their pointsof suspension are at a a. With a view of reducing friction, the axis of motion, c, andboth the points of suspension are knife-edges of ha
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