1. Writing Prompt: 10/26/2006
Predict what will happen if a 250 lb. safety runs into a 140 lb. punt returner who was standing still to catch a punt during a football game?
Write down what will happen to the safety and what will happen to the returner (think about speed and motion)

2. Transfers and Collisions
Momentum
Transfers and Collisions

3. Momentum
What is it?
In general terms: It is when an object picks up speed. To gain momentum you are gaining speed.

4. Momentum What is it? Mathematically: Momentum = Mass X Velocity
p = mv = constant
(lower case “p” stands for momentum)

5. Momentum What is the unit for momentum? Momentum = Mass X Velocity
Mass (kg) X Velocity (m/s) = kg-m/s
Unit is a “kilogram meter per second”

6. Momentum
QUESTION: What is the momentum of a 60 kg Running back running at 3 m/s?
ANSWER: 60 kg x 3 m/s = 180 kg-m/s

7. Conservation of Momentum
Collisions: Two different types
Elastic: Colliding objects DON’T stick together
Example: Bouncing a ball
Plastic: Colliding objects combine into a single object
Example: Firing a bullet into a wood block

8. Conservation of Momentum
If a collision occurs, MOMENTUM IS CONSERVED!!!
Example: If the van hits the car, the final momentum of the two cars will equal their initial momentum!!!

9. Conservation of Momentum
Let’s see a demonstration…

10. Conservation of Momentum
QUESTION: What is the final momentum if a 100 kg cart moving at 3m/s hits another 100 kg cart that isn’t moving and they stick together?
ANSWER: 300 kg-m/s
100 x x 0 = 300

11. Conservation of Momentum
QUESTION: What is the final VELOCITY of the system if a 100 kg cart moving at 3m/s hits another 100 kg cart that isn’t moving and they stick together?
ANSWER: 1.5 m/s
300 kg-m/s = m x v = 200 kg x v
v = 300/200 = 1.5

12. Conservation of Momentum
Let’s see another demo…

13. Conservation of Momentum
Answer the following questions in your comp book from Mr. Darling