The outlines of physics: an elementary text-book . ^ p of mass, is moved to n^. The vertical ^^^ ^^• distance through which it is lifted is Wj^j, with an ex-penditure of work Wi = nj^Pi X mg. If the center of mass is at m^, nearer to o, the same anglecorresponds to a displacement of m^ to n^, with a verticalrise «2^2 ^^^ work The work in the two cases, to which the sensitiveness ofthe balance is inversely proportional, is in the ratio The important features in the construction of the balanceare indicated in Fig. 64. The beam is made of a single piece of metal, designedwith a view to great stif
The outlines of physics: an elementary text-book . ^ p of mass, is moved to n^. The vertical ^^^ ^^• distance through which it is lifted is Wj^j, with an ex-penditure of work Wi = nj^Pi X mg. If the center of mass is at m^, nearer to o, the same anglecorresponds to a displacement of m^ to n^, with a verticalrise «2^2 ^^^ work The work in the two cases, to which the sensitiveness ofthe balance is inversely proportional, is in the ratio The important features in the construction of the balanceare indicated in Fig. 64. The beam is made of a single piece of metal, designedwith a view to great stiffness and to minimum of mass. 80 TEE OVTLlirMS OF PHTSIOS There are three wedges,^ technically called hp,ife-edges: acentral one which forms .the axis of support, and one ateach end, upon which the scale pans hang freely by meansof stirrups. The knife-edges are accurately ground, andare constructed of hardened steel or sometimes of rest against plane bearings of agate. The threeknife-edges are placed in the same horizontal line, and. Fig. 64 this line is located just above the center of mass. A longpointer, which swings in front of a scale, indicates the posi-tion of the beam. A short upright rod, vertically abovethe knife-edges, is threaded and carries a milled nut. Byraising and lowering this nut, the center of mass can beraised and lowered, and the sensitiveness of the balancechanged. The advantages gained by this method of constructionare as follows: (1) Since the scale pans, with their contents, hangfreely from the knife-edges, we may consider their massesas concentrated at a and J, and since these points are atthe same level with 0 and approximately with m thecenter of mass, the balance may he loaded without sensiblyshifting the center of mass. TEE BALANCE 81 (2) By the use of knife-edges two points are gained:(a) The movements of the beam are rendered almost frictionless. (J) The lengths of the arms are accurately fixed andare rendered unchangeable. The lat
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectphysics
