A text-book of physics, largely experimentalOn the Harvard college "Descriptive list of elementary physical experiments." . of CENTRE OF GRAVITY: STABILITY. 93 gravity of a surface etc., when they are met with inbooks on mechanics, may be interpreted to mean centreof gravity of an extremely slender cylinder, of an ex-tremely thin sheet, etc. 81. Stability.—When we speak of the stability of anobject resting upon a supporting surface, we usually havein mind the angle through which it must be tilted to over-turn it. Stability, in the case of rigid bodies, dependsupon two factors, the area of the
A text-book of physics, largely experimentalOn the Harvard college "Descriptive list of elementary physical experiments." . of CENTRE OF GRAVITY: STABILITY. 93 gravity of a surface etc., when they are met with inbooks on mechanics, may be interpreted to mean centreof gravity of an extremely slender cylinder, of an ex-tremely thin sheet, etc. 81. Stability.—When we speak of the stability of anobject resting upon a supporting surface, we usually havein mind the angle through which it must be tilted to over-turn it. Stability, in the case of rigid bodies, dependsupon two factors, the area of the base upon which the bodyrests and the height of the centre of gravity above the estimating the size of the base of an object it must benoticed that, for the purpose of stability, the base consistsof the whole area included by straight lines which con-nect the outermost supporting points all around. Forinstance, the base of a three-legged stool, or a tripod-support for a photographers camera, is a triangle, ofwhich the foot of each leg forms a vertex. In illustration of the influence of the area of the base,. FIG. 57. compare the angle traversed by the centre of. gravity of asquare prism, A (Fig. 57), 1 cm. square and 10 cm. long,placed on end and then overturned, with the angle traversedunder similar conditions by the centre of gravity of a de-cimeter cube, B. The block A will not of itself overturnuntil its diagonal AF has passed the vertical posi- 94 PHYSICS. tion which it has in the figure. In the same way B willof itself overturn only after BG has passed the verticalposition. To be upset, therefore, the block A has to betilted only a bit more than the very small angle EFC,while the block B has to be tilted a bit more than the angleHGl, of 45°. In order to show the influence of the height of the centrecf gravity on stability, suppose a heavy iron nut, with ahole 1 cm. or more in diameter, to have a cylindrical pieceof wood inserted in it. When the nut is ne
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