- We know how to calculate the
**kinetic energy**of moving objects -- isn't that enough? No. It turns out that many situations involving**collisions**do not obey the simple conservation of Mechanical Energy. Why not? Because it takes energy to bend, break, mutilate and deform objects, energy which disappears from the kinetic and gravitational potential energy. - But a different quantity
*is conserved,*even during collisions. The**linear momentum**of an object is defined asp = (mass) * (velocity)

It is a vector quantity, and the total linear momentum of a bunch of objects will remain the same, before and after a collision. - Momentum is connected to force by
**impulse**, which is simplyimpulse = (force) * (time)

if the force has a constant magnitude during its action. If the force changes with time, then one must integrate to find the impulse:/ impulse = | (force) dt /

- The Momentum-Impulse Theorem states that the change in
momentum of an object is equal to the impulse exerted on it:
(change in momentum) = (impulse) p - p = (force) * (time) final initial m*v - m*v = (force) * (time) final initial

Viewgraph 1

Viewgraph 2

Viewgraph 3

Viewgraph 4

Viewgraph 5

Viewgraph 6

Viewgraph 7

Viewgraph 8

Viewgraph 9

Viewgraph 10