Word Study
hodograph
CIDE DICTIONARY
hodograph, n. [Gr. path + graph.].
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. [1913 Webster]
OXFORD DICTIONARY
hodograph, n. a curve in which the radius vector represents the velocity of a moving particle.
Etymology
Gk hodos way + -GRAPH
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