Impetus /(ĭm"pē̇*tŭs)/

Im·pe·tus

Impetus

n.
  1. A property possessed by a moving body in virtue of its weight and its motion; the force with which any body is driven or impelled; momentum.
  2. Fig.: Impulse; incentive; stimulus; vigor; force; as, the President's strong recommendation provided the impetus needed to pass the campaign reform bill.
  3. The altitude through which a heavy body must fall to acquire a velocity equal to that with which a ball is discharged from a piece. (Gun.)