Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/389

Rh unite there, and be formed into a globe. And therefore if the common centre of gravity of the attracting bodies be either at ret, or proceeds uniformly in a right line; the attracted body will move in an ellipis having its centre in the common centre of gravity of the attracting bodies.

If to the everal points of any circle there tend equal centripetal forces, increaing or decreaing in any ratio of the ditances; it is required to find the force with which a corpucle it attracted, that is ituate any where in a right line which tands at right angles to the plane of the circle at its centre.

Suppoe a circle to be decribed about the centre A (Pl. 24. Fig. 1.) with any interval AD in a plane to which the right line AP is perpendicular; and let it be required to find the force with which a corpucle P is attracted towards the ame. From any point E of the circle, to the attracted corpucle P, let there be drawn the right line PE. In the right line PA take PF equal to PE, and make a perpendicular FK, erected at F, to be as the force with which the point E attracts the corpucle P. And let the curve line IKL