The Collaborative International Dictionary
Parallelogram \Par`al*lel"o*gram\, n. [Gr. ?; ? parallel + ? to write: cf. F. parall['e]logramme. See Parallel, and -gram.] (Geom.) A right-lined quadrilateral figure, whose opposite sides are parallel, and consequently equal; -- sometimes restricted in popular usage to a rectangle, or quadrilateral figure which is longer than it is broad, and with right angles.
Parallelogram of velocities, parallelogram of forces, parallelogram of accelerations, parallelogram of momenta, etc. (Mech.), a parallelogram the diagonal of which represents the resultant of two velocities, forces, accelerations, momenta, etc., both in quantity and direction, when the velocities, forces, accelerations, momenta, etc., are represented in quantity and direction by the two adjacent sides of the parallelogram.
Usage examples of "parallelogram of velocities".
In this assertion we encounter a misconception exactly like the one in the statement that the theorem of the parallelogram of forces follows by logical necessity from the theorem of the parallelogram of velocities.