. A text book of elementary mechanics, for the use of colleges and schools. Fig. 135. always acts vertically (Fig. 135) and turns the leverfrom the position AB to that of AB\ then the effective 190.] LEVEE. 201 distance through which it acts is AC (~ s), and theheight through which the weight is raised is BD (= h).Therefore P^ ITD _ ITF BF W ZZ AC ZZ AF ~ AF; .-. = , as in Art. 186. (2) Suppose the power and resistance to act continu-ally at right angles, to the straight lever AB (Fig. 136). Fig. 136. while it turns from the position AB to A SB. Here thepower acts through the arc A A
. A text book of elementary mechanics, for the use of colleges and schools. Fig. 135. always acts vertically (Fig. 135) and turns the leverfrom the position AB to that of AB\ then the effective 190.] LEVEE. 201 distance through which it acts is AC (~ s), and theheight through which the weight is raised is BD (= h).Therefore P^ ITD _ ITF BF W ZZ AC ZZ AF ~ AF; .-. = , as in Art. 186. (2) Suppose the power and resistance to act continu-ally at right angles, to the straight lever AB (Fig. 136). Fig. 136. while it turns from the position AB to A SB. Here thepower acts through the arc A A (= s), and the resist-ance is overcome through the distance of the arc BB(= d). Hence P_ B& BF, R z:z AA Z:Z AF; .% = In general, the relation may be obtained after the samemanner, whatever the shape of the lever or the directionsof P and W (or B). In each case, however, it must beremembered that s and h (or d) are not necessarily theactual, but always the effective, distances. 202 STATICS. [191. B. Some Special Applications of the Principle of the Lever. I. BALANCE. 191. The Balance is a contrivance used for measur-ing the mass of bodies ; or, in familiar language, of deter-mining their weight by comparison with that of certainassumed units. (See Arts. 54, 55.) In its ordinary formit consists of a beam, so constructed as to be at once strong,rigid, and light. This beam is poised on a knif e-edge, inthe middle, as a fulcrum, often resting on a plate of the extremitie
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