hodograph

noun

1. A curve described by the moving extremity of a line whose other end is fixed, this line being constantly parallel to the direction of motion of, and having its length constantly proportional to the velocity of, a point moving in any path; used in investigations respecting central forces.

   “The following is Sir W R. Hamilton's theorem of hodographical isochranism: "if two circular hodegraphs having a common chord, which passes through or tends towards a common centre of force, be cut perpendicularly by a third circle, the times of hodographically describing the intercepted arcs will be equal."”