1. Momentum

2. Momentum and Sports
"Going into the all-star break, the Chicago White Sox have the momentum."
"Chicago Bears Gaining Momentum."
"You have the momentum; the critical need is that you use that momentum and bury them in this third quarter." – A quote from a coach trying to pump up his team!!
What do all these phrases have in common?
MOMENTUM

3. Momentum is commonly used in sports. A team that has the
momentum is on the move
and is going to take some
effort to stop.
Momentum refers to the
quantity of motion that an
object has.
A sports team which is "on the move" has the momentum.
An object in motion ("on the move") then has momentum.

4. What is Momentum? Momentum can be defined as “mass in motion.”
All objects have mass; so if
an object is moving, then it has
momentum - it has its
MASS IN MOTION.
The amount of momentum which
an object has is dependent upon two variables…
Mass and Velocity
In other words, how much stuff is moving and how fast the stuff is moving

5. How can you remember?

6. Equation Momentum = mass * velocity p=m*v Units??
kgm/s
What is the momentum of a 60-kg halfback moving eastward at 9 m/s?
p=(60kg)(9m/s)
p=540kgm/s

7. p=mv
The equation illustrates that momentum is directly proportional to an object's mass and to the object's velocity.
An object has a large momentum if it has a large mass or a large velocity, and both variables are of equal importance in determining the momentum of an object.

8. EXAMPLE
Consider a Mack truck and a roller skate moving down the street at the same speed.
Which will have a greater momentum?
The considerably greater mass of the Mack truck gives it a considerably greater momentum
Consider that the same Mack truck is at rest, but the roller skate is moving.
The roller skate.
Anything at rest has a momentum of “0”.
It is not an “mass in motion.”

9. Impulse To stop such an object, it is necessary to apply a…
Force
AGAINST
To stop such an object, it is necessary to apply a force against its motion for a given period of time

10. The more momentum
an object has, the harder
that is to stop
It would require a
greater amount of force
or a longer amount of time
(or both) to bring an object
with more momentum to a halt.

11. This is called an impulse
Impulse=change in momentum
or Ft=Δmv

12. ESPN Video Questions
1. Explain why the goal posts have padding around their base.
The padding will increase the time required to stop and decrease the force.

13. 2. A 90 kg football player is moving at 7m/s
2. A 90 kg football player is moving at 7m/s. Calculate the force required to stop him in .4 seconds; in .2 seconds; in .1 seconds.
Ft=Δmv
F= Δmv/t
F=(90)(7)/(.4)
F=1575N

14. 3. Examine the inside of a football helmet
3. Examine the inside of a football helmet. How is the helmet constructed so that the player’s head will have more time to stop during a collision? Why do we want to give the head more time to stop?
There is space in the interior of the helmet for the head to move, thereby increasing the time.

15. 4. List safety features in cars which lengthen the time during a collision in order to decrease the maximum force during that collision.