The Physics of Ice Hockey
Ice hockey is definitely the most brutal form
of hockey. Many violent collisions, fights, and bodychecks occur during every
game. That is why it is perfectly appropriate to demonstrate the rules of
momentum, impulse, and collisions using examples from ice hockey.
To successfully understand how momentum and
impulse apply to ice hockey, it really helps to have a strong understanding of
what they are. Momentum is defined as the MASS of an object times its VELOCITY,
or P=mv. Impulse is known as simply the change of momentum, and is formally
defined as the product of the force exerted to change the momentum and the time
it took to do that (I=Ft).
PROBLEM #1:
Lets say a 5’3" 50 kg. right wing skates at 7
m/s. If a 6’2" 85 kg. defenseman skates at the same rate, who has the greater
momentum? How much greater?
OBSERVE:
P=(50 kg.)(7 m/s) P=(85
kg.)(7 m/s)
= 350 kg.m/s = 595
kg.m/s 
The defenseman has a significantly larger
momentum than the right wing. The difference is 245 kilogram meter per
seconds.
PROBLEM #2:
If the same 85 kg. defenseman gets angry
with you (watch out!), and decides to exert a 600 N (Newton) force by punching
you in the face, and exerts this force for .9 seconds, what is your change in
momentum? (HINT: this is the same as the impulse you are exhibiting).
OBSERVE
I=(600 N)(.9
sec.)
= 540 kg.m/s
There are two extremities in types of
collisions: totally elastic and totally inelastic. Both of these types of
collisions can be frequently observed while watching your typical NHL ice hockey
game.
Here is an example of a near
totally elastic collision; after hitting each other, both players bounce off
each other like rubber balls, and almost no kinetic energy is lost.

In this photo, after colliding with
each other, the two players almost become one, and have lost virtually all
of their kinetic energy. They probably saw each other in just enough time
to latch on to the other one, and therefore are a prime example of an
almost totally inelastic
collision. 