1. October 9, 2017
Momentum

2. Drill Take out Drills + Classwork from last week + Lab Reports
An astronaut with a mass of 87 kg, wears a space suit with a mass of 28 kg. If the astronaut walks on the moon at a rate of 2.9 m/s eastward, what is the magnitude of the momentum of the astronaut and his suit in kgm/s?

3. Momentum Video: https://www.youtube.com/watch?v=HEITsfVpie0
What factors contribute to the seriousness of the injury that the football players get when they are hit?
Why did the narrator in the video mention “speed” several times?
What does speed have to do with the hit that the players receive during the game?

4. Momentum Defined as "mass in motion."
All objects have mass… if an object is moving, then it has momentum.
Amount of momentum is dependent upon two variables:
Mass
Velocity
Unit = kg*m/s
Direction of velocity vector = direction of momentum vector.

5. Momentum
Object with large mass and large velocity has a large momentum.
p =mv … tells us that both mass and velocity are equally important when calculating momentum.
Momentum of any object at rest = zero.
Is it possible for a baseball to have greater momentum than a bus?

6. True or False Momentum is a vector quantity.
The standard unit on momentum is the Joule.
An object with mass will have momentum.
An object which is moving at a constant speed has momentum.
An object can be traveling eastward and slowing down; its momentum is westward.

7. True or False
The momentum of an object varies directly with the speed of the object.
Two objects of different mass are moving at the same speed; the more massive object will have the greatest momentum.
A less massive object can never have more momentum than a more massive object.
Two identical objects are moving in opposite directions at the same speed. The forward moving object will have the greatest momentum.
An object with a changing speed will have a changing momentum.
m.

8. Exit Ticket
If a gazelle with a mass of kg and is running northward with a velocity of 16.1 m/s, then with what velocity must a lion run with a mass of 42.6 kg to have the same momentum as the gazelle?
A 30-kg child rides a 20-kg bicycle. Together, the child and the bicycle have a momentum of 110 kgm/s. What is the velocity of the boy and the bicycle?
 A car that drives at m/s has a momentum of kgm/s. What is the mass of the car?
A truck driving along a highway road has a large quantity of momentum. If it moves at the same speed but has twice as much mass, how would its new momentum compare to what it has initially?
60.6 m/s
2.2 m/s
1215 kg
Momentum will double

9. Conservation of Momentum
October 10, 2017
Conservation of Momentum

10. Drill – Calculate the Momentum of Each Car

11. What is conservation?

12. Vocabulary Terms
Closed system = objects do not gain or lose mass after a collision.
Can include any number of objects.
Objects can stick together or come apart after collision.
Internal forces = all forces within the closed system.
External forces = all forces outside of the closed system.

13. Law of Conservation of Momentum
The total momentum of a closed system, with no external forces, is the same before and after a collision.
Total momentum of the system before collision is equal to the total momentum after collision.
Did the system remain closed (no change in total mass)?
Did external forces act on the system?

14. Examples
Two cars drive at constant speed north on the highway. A third car gets on the highway at the same speed.
One ice skater pushes another and they go in opposite directions.
A brick slows down when acted on by the outside force of friction.

15. Types of Collisions – GENERAL
Two objects move toward each other  collide  move away from each other.
Example: kicking a ball
Equation:
p1o + p2o = p1f + p2f
(m1)(v1o) + (m2)(v2o) = (m1)(v1f) + (m2)(v2f)

16. Types of Collisions – STICKY
Two objects move toward each other  collide  stick together and move as a unit.
Example: car crash, space
Equation:
Ends with one total mass and same velocity
(m1)(v1o) + (m2)(v2o) = (m1 + m2)(vf)

17. Types of Collisions – RECOIL
Two objects start with zero total momentum  move away from each other in opposite directions.
Example: gun, cannon
Equation:
Initial momentum = zero
0 = (m1)(v1f) + (m2)(v2f)

18. Conservation of Momentum
October 11, 2017
Conservation of Momentum

19. Newton’s Cradle