Momentum :  (noun)
1: an impelling force or strength; "the car's momentum carried it off the road" [syn: impulse]
2: the product of a body's mass and its velocity; "the momentum of the particles was deduced from meteoritic velocities"

clout, compulsion, drive, driving force, energy, force, impellent, impelling force, impetus, impulse, impulsion, incentive, incitement, inertia, irresistible force, moment, motive power, power, propulsion, push, strength, thrust,