. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. PRESENT FUNDAMENTAL CONCEPTIONS OF PIIYSICS. 493 conclusions to be drawn from them. The short space of time allotted us obliges us to use economy, and therefore we limit ourselves to the indispensable in this direction. First, however, it will be necessary to define what (according to Poncelet and Coriolis) is termed " work " in scientific language, how it is measured and calculated. Whatever effect of any power we may subject to
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. PRESENT FUNDAMENTAL CONCEPTIONS OF PIIYSICS. 493 conclusions to be drawn from them. The short space of time allotted us obliges us to use economy, and therefore we limit ourselves to the indispensable in this direction. First, however, it will be necessary to define what (according to Poncelet and Coriolis) is termed " work " in scientific language, how it is measured and calculated. Whatever effect of any power we may subject to analysis, we shall always arrive at the result that the " work" performed by a force consists in the overcoming of a resistance within a given distance. For instance, if a force has to overcome a ten times greater resistance over the same space, its work will be ten times greater, and so the labor of a force is three times greater if it overcomes a uniform resistance over a three times greater space. The amount 01 work by a force, therefore, increases in proportion to the resistance which is overcome and to the length of way over which the resistance has been overcome. If the work of forces is to be expressed by numbers, it is necessary to name a work unit. The work required to lift 1 leg. through 1 meter is called a kilogram-meter or meter-kilogram (kgm), ami is regarded as the work-unit. If then there is a resistance of 10 Tegs, to be overcome through the space of one meter, the work is 10 Jcgms.; but if this resistance is to be overcome over three meters, the work will be three times 10 kilogram-meters, that is, 30 legms. We see from this that the amount of any work is calculated by multiplying the distance by the force. We are now enabled to include within our ex- aminations the most easily comprehensible of Joule's experiments. A perpendicular axis of ro- tation, A A, (see figure,) ^provided with brass pad- dles F F,—having their planes F in an upright position
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