Guy's Elements of astronomy : and an abridgment of Keith's New treastise on the use of the globes . un must appear little more than a fixed star. If a body at rest receives two impulses at the same time, from forces indifferent directions, it will be made to move in a line that lies betweentiie direction of the forces impressed. If on the ball A (Plate IX. ,) a force be impressed sufficient to make it move with a uniform velocity to the point B. in a second of time ; and if another force be alsouiipressed on the ball w-hich would make it move to C, in the sametime, the ball by means of th
Guy's Elements of astronomy : and an abridgment of Keith's New treastise on the use of the globes . un must appear little more than a fixed star. If a body at rest receives two impulses at the same time, from forces indifferent directions, it will be made to move in a line that lies betweentiie direction of the forces impressed. If on the ball A (Plate IX. ,) a force be impressed sufficient to make it move with a uniform velocity to the point B. in a second of time ; and if another force be alsouiipressed on the ball w-hich would make it move to C, in the sametime, the ball by means of the two forces acting lo^etlier, will describe%e line A a D. In the beginning the Grand Mover :ed such a degree of mo-tion upon these bodies as if not controlled would have whirled themciriwards in straight lines to endless lenp;ths till they would have beenlost to imagination in the abyssj of space ; but the graviiaiing poweicombmed wi*^b th^ -rfonprfiJ^; df^tennines their courees to an elliptirai(orm, and obliges these bodies to nerform their destined rounds //,,/ A/./ /. V s I \ .. ^ 3 Ihira^, . l-ifli PVit^ 0]S THE CENTRE OF GRAVITY. 67 CHAPTER XIX. ON THE CENTRE OF GRAVITY. Fme Centre of Gravity is that point of the body, inwhich its whole weight is, as it were, concentrated, andupon which, if the body be freely suspended, it willrest. A weight of 1 cwt. at 10 feet fix)m a prop, will balance another cf10 cv/t at 1 foot from it; or Let two weights (Plate X. fig. 6) be nicely poised ona centre, round which they may freely turn: theheaviest, of 10 cwt., would move in a circle whose ra-dius or distance from ^be centre would be one foot,while the lightest, of 1 cwt., would move in a circlewhose radius would be 10 feet; the centre round whichthey move is the centre of gravity. And thus the sun and planets move round an ima-ginary point as a centre, always preserving an equilib^rium. If the earth were the only attendant on the sun, as his .quantity olmatter is 200,000
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectastronomy, bookyear18
