1. Handout, Test Correction, Copy down table
Objects
Pbefore (kg*m/s)
Pafter (kg*m/s)
Object 1
Object 2
Total

2. Announcement 1: 3CM Validity

3. Worksheet is homework for the weekend, but bring it in tomorrow – we will be solving problems together from there
Announcement 2:

4. Momentum Objectives (Mom. and Energy Unit)
Define and calculate the momentum of an object. 
Determine the impulse given to an object. 
Interpret and use force vs. time graphs (Base x Height). 
Apply conservation of momentum to solve a variety of problems. 
Distinguish between elastic and inelastic collisions. 

5. Big idea: Conservation of Momentum
Examples: Gun recoil, fireworks, stuck in space
* Last formula under mechanics

6. Using tables to Solve Word Problems
Objects
Pbefore (kg*m/s)
Pafter (kg*m/s)
Object 1
Object 2
Total

7. Example 1
A 2000-kg car traveling at 20 m/s collides with a 1000-kg car at rest at a stop sign. If the 2000-kg car has a velocity of 6.67 m/s after the collision, find the velocity of the 1000-kg car after the collision.

8. Objects Pbefore (kg*m/s) Pafter (kg*m/s) Car A Car B Total
A 2000-kg car traveling at 20 m/s collides with a 1000-kg car at rest at a stop sign. If the 2000-kg car has a velocity of 6.67 m/s after the collision, find the velocity of the 1000-kg car after the collision.
Objects
Pbefore (kg*m/s)
Pafter (kg*m/s)
Car A
Car B
Total

9. Objects Pbefore (kg*m/s) Pafter (kg*m/s) Car A (2000)(20) = 40,000
A 2000-kg car traveling at 20 m/s collides with a 1000-kg car at rest at a stop sign. If the 2000-kg car has a velocity of 6.67 m/s after the collision, find the velocity of the 1000-kg car after the collision.
Objects
Pbefore (kg*m/s)
Pafter (kg*m/s)
Car A
(2000)(20) = 40,000
Car B
(1000)(0) = 0
Total
40,000

10. Objects Pbefore (kg*m/s) Pafter (kg*m/s) Car A (2000)(20) = 40,000
A 2000-kg car traveling at 20 m/s collides with a 1000-kg car at rest at a stop sign. If the 2000-kg car has a velocity of 6.67 m/s after the collision, find the velocity of the 1000-kg car after the collision.
Objects
Pbefore (kg*m/s)
Pafter (kg*m/s)
Car A
(2000)(20) = 40,000
(2000)(6.67) = 13,340
Car B
(1000)(0) = 0
(1000)(VB) = 1000VB
Total
40,000
13, VB

11. Example 1: Problem (step 2: solving)
(1) Table
Objects
Pbefore (kg*m/s)
Pafter (kg*m/s)
Car A
(2000)(20) = 40,000
(2000)(6.67) = 13,340
Car B
(1000)(0) = 0
(1000)(VB) = 1000VB
Total
40,000
13, VB
(2) Math to solve for final Vb
Pbefore = Pafter
40,000 = 13,340 + (1000)Vb
26,660 = 1000Vb
26.7 = Vb
Vb = 26.7 m/s

12. Example 2
On a snow-covered road, a car with a mass of 1100 kg collides head- on with a van having a mass of 2500 kg traveling at 8 m/s. As a result of the collision, the vehicles lock together and immediately come to rest. Calculate the speed of the car immediately before the collisions. [Neglect friction]

13. On a snow-covered road, a car with a mass of 1100 kg collides head-on with a van having a mass of 2500 kg traveling at 8 m/s. As a result of the collision, the vehicles lock together and immediately come to rest. Calculate the speed of the car immediately before the collisions. [Neglect friction]
Pbefore (kg*m/s)
Pafter (kg*m/s)
Car
Van
Total

14. Car 1100*Vcar = 1100Vcar Van 2500*(-8) = -20,000 Total
On a snow-covered road, a car with a mass of 1100 kg collides head-on with a van having a mass of 2500 kg traveling at 8 m/s. As a result of the collision, the vehicles lock together and immediately come to rest. Calculate the speed of the car immediately before the collisions. [Neglect friction]
Pbefore (kg*m/s)
Pafter (kg*m/s)
Car
1100*Vcar = 1100Vcar
Van
2500*(-8) = -20,000
Total
1100Vcar – 20,000

15. Car 1100*Vcar = 1100Vcar Van 2500*(-8) = -20,000 Total
On a snow-covered road, a car with a mass of 1100 kg collides head-on with a van having a mass of 2500 kg traveling at 8 m/s. As a result of the collision, the vehicles lock together and immediately come to rest. Calculate the speed of the car immediately before the collisions. [Neglect friction]
Pbefore (kg*m/s)
Pafter (kg*m/s)
Car
1100*Vcar = 1100Vcar
Van
2500*(-8) = -20,000
Total
1100Vcar – 20,000

16. Example 2: Problem (step 2: solving)
(1) Table
(2) Math to solve for final V
1100Vcar – 20,000 = 0
Vcar = 20,000/1100
Vcar = 18.2 m/s
Pbefore (kg*m/s)
Pafter (kg*m/s)
Car
1100*Vcar = 1100Vcar
Van
2500*(-8) = -20,000
Total
1100Vcar – 20,000

17. Example 3
A 4-kg rifle fires a 0.02-kg shell with a velocity of 300 m/s. Find the recoil velocity of the rifle.

18. A 4-kg rifle fires a 0. 02-kg shell with a velocity of 300 m/s
A 4-kg rifle fires a 0.02-kg shell with a velocity of 300 m/s. Find the recoil velocity of the rifle.
Pbefore (kg*m/s)
Pafter (kg*m/s)
Rifle
Shell
Total

19. A 4-kg rifle fires a 0. 02-kg shell with a velocity of 300 m/s
A 4-kg rifle fires a 0.02-kg shell with a velocity of 300 m/s. Find the recoil velocity of the rifle.
Pbefore (kg*m/s)
Pafter (kg*m/s)
Rifle
Shell
Total

20. A 4-kg rifle fires a 0. 02-kg shell with a velocity of 300 m/s
A 4-kg rifle fires a 0.02-kg shell with a velocity of 300 m/s. Find the recoil velocity of the rifle.
Pbefore (kg*m/s)
Pafter (kg*m/s)
Rifle
4*Vrecoil
Shell
(.02)(300) = 6
Total
6 + 4Vrecoil

21. Example 3: Problem (step 2: solving)
(1) Table
(2) Math to solve for final V
0 = 6 + 4Vrecoil
Vrecoil = -6/4 =
Vrecoil = m/s
Pbefore (kg*m/s)
Pafter (kg*m/s)
Rifle
4*Vrecoil
Shell
(.02)(300) = 6
Total
6 + 4Vrecoil

22. Elastic vs Inelastic Collisions and Explosions
Elastic Collisions are collisions where two objects bounce off of each other [Note: Kinetic Energy is conserved]
Inelastic Collisions are collisions in which two objects collide and stick to each other [Note: Kinetic energy is not conserved because internal energy is produced]
Explosions result from a single object being broken up into two or more parts