Fifth book of lessons for the use of schools . whilst the suns attraction would bringit to c in the same space of time. Reasoning upon thelaws of uniform motion we might hastily conclude thatthe earth would move in the diagonal A D of the paral-lelogram A B D c, as & ball struck by two forces will the force of attraction is continually acting uponour terrestrial ball, and producing an incessant deviationfrom a course in a straight line, and thus converts itinto a course in a curve line. Let us detain the earth a moment at the point D, andconsider how it will be affected by the combined
Fifth book of lessons for the use of schools . whilst the suns attraction would bringit to c in the same space of time. Reasoning upon thelaws of uniform motion we might hastily conclude thatthe earth would move in the diagonal A D of the paral-lelogram A B D c, as & ball struck by two forces will the force of attraction is continually acting uponour terrestrial ball, and producing an incessant deviationfrom a course in a straight line, and thus converts itinto a course in a curve line. Let us detain the earth a moment at the point D, andconsider how it will be affected by the combined actionof the two forces in its new situation. It still retainsits tendency to fly off in a straight line; but a straightline would now carry it away to F, whilst the sun wouldattract it in the direction D s. In order to knowexactly what course the earth will follow, another paral-lelogram must be drawn in the same manner as thefirst; the line D F describing the force of projection,and the line D s that of attraction; and it will be found. TUE EARTHS ANNUAL MOTION. 291 that the earth will proceed in the curve line D a drawnin the parallelogram d f G e ; and if we go on through-out the whole of the circle, drawing a line from theearth to the sun, to represent the force of attraction,and another at a right angle to it, to describe that ofprojection, we shall find that the earth will proceed in acurve line passing through similar parallelograms till ithas completed the whole of the circle. The attractionof the sun is the centripetal force, which confines theearth to a centre; and the impulse of projection, or theforce which impels the earth to quit the sun and fly off,is the centrifugal force. We have described the earth as moving, in a circle,merely to render the explanation more simple, for inreality the centripetal and centrifugal forces are not soproportioned as to produce circular motion; and theearths orbit or path round the sun is not circular, butelliptical or oval. Let us
Size: 1753px × 1426px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1860, bookpublishermontrealjohnlovell
