[电] 速度图

Hodograph \Hod"o*graph\, n. [Gr.? path + graph.] (Math.)
A curve described by the moving extremity of a line the other
end of which 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.