When
a particle with mass m moves
with velocity v, we define
its momentum p, as

p = mv

Momentum
is
a Vector

The
total momentum of a system is constant whenever the vector
sum of the external forces on the system is zero. In particular,
the total momentum of an isolated system is constant.

Conservation
of Momentum
is true in all dimensions

Elastic
and Inelastic Collisions

Momentum
is always conserved.

Kinetic Energy is not necessarily
conserved in all collisions.

An Inelastic Collision - Animation

The
Ballistic Pendulum click on the diagram to the right

The time that
the Force is applied. . . an important approximation

An
applied force
acting on a particle may vary in time.

The impulse
imparted to the particle by the applied
force is the area under the curve.

In the time interval t, the time-averaged force gives
the same impulse
to the particle as does the time varying applied
force.

How does the
time of the collision relate to the Force of the collision?