1. Impulse and Momentum

2. Momentum and Collisions
The goal with lesson is to understand inertia and motion. Momentum helps us understand collisions.
Elastic Collisions - objects rebound
Inelastic Collisions - object stick together an usually become distorted and generate heat

3. Momentum Momentum = mass ´ velocity p = mv
Momentum is a vector quantity.

4. Large Momentum Examples
Huge ship moving at a small velocity
High velocity bullet
P = Mv
P = mv

5. Momentum Examples
A large truck has more momentum than a car moving at the same speed because it has a greater mass.
Which is more difficult to slow down? The car or the large truck?

6. Impulse Newton’s Second Law can read F = ma F = m(Dv÷Dt)
F = (Dmv)÷(Dt)
F· ∆t = (Dp) ÷(∆t) ∙∆t
Impulse (∆p)=FDt

7. When Force is Limited Apply a force for a long time. Examples:
Follow through on a golf swing.
Pushing a car.
FDt

8. Minimize the Force
Increase Dt
Catching a ball
Bungee jumping
FDt

9. Maximize Momentum Change
Apply a force for a short time.
Examples:
Boxing
Karate
FDt

10. Conservation of Momentum
This means that the momentum doesn’t change.
Internal forces cannot cause a change in momentum.

11. Collisions
Before m2 m1
After m1 m2

12. Inelastic Collisions v = 10 v = 0 M M Before Collision p = Mv v’ = 5 M
After Collision
p = 2Mv’
Mv = 2Mv’
v’ = ½ v

13. Elastic Collisions Conserve Energy and Momentum Before Collision
Equal masses
Case 1:
Case 2:
M > M
Case 3:
M < M

15. Things I Understand… I Need to Know more of…

16. Conservation in Momentum
1. A 12,000kg. railroad car is traveling at 2m/s when it strikes another 10,000kg.railroad car that is at rest. If the cars lock together, what is the final velocity of the two railroad cars? 
2. A 9,300 kg. railroad car traveling at a velocity of 15m/s strikes a second  boxcar at rest. If the two cars stick together and move off with a velocity of 6m/s, what is the mass of the second car?
3. A 25 gram bullet is fired from a gun with a speed of 230m/s. If the gun has a mass of 0. 9kg. What is the recoil speed of the gun?
4. A 20 gram bullet traveling at 250m/s strikes a block of wood that weighs 2kg. With what velocity will the block and bullet move after the collision?
Conservation in Momentum

17. Impulse Impulse=FDt
A rocket engine fires for 10 seconds while providing 4,000 N of thrust. What impulse is given to the rocket by its engines?
A 500-g baseball is given an impulse of 12.5 N-s by a baseball bat. The bat is only in contact with the ball for 0.10 seconds. What is the average force of the bat acting on the ball?