An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Of a force acting on a body, the → product of the → force and the → time for which it acts. If the force changes with time, the impulse is the → integral of the force with respect to the time during which the force acts, and is equal to the total change of → momentum produced by the force: ∫F dt = ∫m dv. Impulse is a → vector quantity.

From L. impulsus "a push against, pressure, shock," p.p. of impellere "to push, strike against, drive forward," from → in- "into" + pellere "to push, drive."

Tekâné, from tekân "involuntary motion, sudden shaking," related to tak "rush, quick motion, stroke, blow" (tâxtan, tâzidan "to run; to hasten; to assault"); Mid.Pers. tak "assault, attack;" Av. taka- "leap, run," from tak- "to run, flow;" cf. Skt. tak- "to rush, to hurry," takti "runs;" O.Ir. tech- "to flow;" Lith. teketi "to walk, to flow;" O.C.S. tešti "to walk, to hurry;" Tokharian B cake "river;" PIE base *tek^w- "to run; to flow;" → flow.

The vector → impulse of the → resultant force on a particle, in any time interval, is equal in magnitude and duration to the vector change in momentum of the particle: ∫F dt = mv₂ - mv₁. The impulse-momentum principle finds its chief application in connection with forces of short duration, such as those arising in collisions or explosions. Such forces are called → impulsive forces.

→ impulse; → momentum; → principle.