|The change in motion
is proportional to the motive force impressed; and is made in the direction of the right
[straight] line in which that force is impressed. Hence, p is parallel to Fav and
putting it all together symbolically, we have:
Fav = p/t
The average net force equals the time-rate-of
change of momentum. It is useful to combine the force and time into a single notion
that equals the known momentum change. This concept of change in momentum is called impulse.
Favt = p
This is the measure of the force and the
length of time that the force actually acts.
Momentum, like gravitational potential energy,
spring energy, etc. is a conserved quantity, as the Law of Conservation of
total momentum of objects before = total
momentum of objects after.
Thus along with work and energy, momentum is
an additional factor one considers when analyzing motion problems, particularly problems
involving collisions or explosions.