Impulse

(im'püls.) [From L. impulsus, driven.] (Phys.) The single or momentary force with which a body is impelled by another body striking it. The strictly mathematical definition of an impulse is the limit of a force which is infinitely great, but acts only during an infinitely short time. There are, of course, no forces in nature exactly fulfilling the conditions of this definition, but there are forces which are very great, and act only during a very short time, as, for example, the blow of a hammer. Such forces are treated as impulses, they are measured by the whole momentum generated by the impulse. [s. 479]