Farrow's military encyclopedia : a dictionary of military knowledge . to rise from it at any angle by insirrt-ing a wedge, iiro|MTly i]re|mreil as seen in tlie ( I! Jiangs a bar gradiialiMl in inches, by whichthe height of I lie plane can be at once carriage, W, (-onstitntes the weight, and thepower, 1, acts on it in a direction parallel to thelonglh of the |ilane. Xow make P balance; W, andthen measure the height anil length of the plane;it will be fiiiiiid that P is to W as the height, of thepliine is to its ; that is, the power multipliediiy the number of
Farrow's military encyclopedia : a dictionary of military knowledge . to rise from it at any angle by insirrt-ing a wedge, iiro|MTly i]re|mreil as seen in tlie ( I! Jiangs a bar gradiialiMl in inches, by whichthe height of I lie plane can be at once carriage, W, (-onstitntes the weight, and thepower, 1, acts on it in a direction parallel to thelonglh of the |ilane. Xow make P balance; W, andthen measure the height anil length of the plane;it will be fiiiiiid that P is to W as the height, of thepliine is to its ; that is, the power multipliediiy the number of iiulies in the length will be equal1(1 the weight iiiiilliplied by the niuiilier of inches inthe height. By varying the experiment, so that llicpower might act in a (lirection jiarallel to the base,we would lind (hat there would he equilibriuin whenthe jiower multiiilied liy the base equals the weightniiiltiplicd by tlie height. Two inclined planes]ilaced base to base form a Wedr/e. It is much usedill splitting wood, as in Fig. 20; it is also used forraising great. Fii;. 20. weights through small distances. In dockyards,ships are raised on the stocks by wedges driven un-der their keels. Theoretically considered, the me-chanical advantage of the isosceles wedge is the sideof the wedge divided by half the back. But thisgives us no idea of the real advantage of the ma-chine : this arises from its enormous friction, andalso because the force wliicli urges it is derived fromthe blow of a hammer or a mallet,etc.; a force so very different in itsnature from the resistance that it hasto overcome, which is the pressnrc ofsome weight or the cohesion of theparticles of a body, that it admits ofno numerical comparison. One partof the theory is true: that the small-er the back the greater is the advan-tage of the wedge. If a flexible in-clined plane, A—one made of paper,for example—be wrapped round acylinder, B, as in Fig. 2i, a screw isformed. By means of the apparatusin Fig. 23 we can
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Keywords: ., bookcentury1800, bookdecade188, booksubjectmilitaryartandscience
