Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/244



Of the invention of orbits wherein bodies will revolve, being acted upon by any ort of centripetal forces.

If a body, acted upon by any centripetal force, if any how moved, and another body acends or decends in a right line; and their velocities be equal in any one cae of equal altitude, their velocities will be alo equal at all equal altitudes.

Let a body decend from A (Pl. 17. Fig. 3.) through D and E, to the centre C, and let another body move from V in the curve line VIKk. From the centre C, with any ditances, decribe the concentric circles DI, EK, meeting the right line AC in D and E, and the curve VIK in I and K.