1. Momentum Mo or 

2. What is Momentum? A quantity of motion Tells that an object is on the move and hard to stop Mass in motion

3. Momentum Formula Involves mass and velocity (so direction is important!) Momentum = Mass x Velocity Mo = MV (  = MV) So… V = Mo/M and M = Mo/V The unit is a mass unit x a speed unit so… kg*m/s or kg*km/hr or g*cm/s… (it can’t be simplified more than this!)

4. Lets Try a problem! These cars are about to collide… (on ice!) Mass: 300 kgMass: 250 kg Velocity: 20 km/hrVelocity: 12 km/hr Mo = 300 kg x 20 km/hr Mo = 250 kg x 12 km/hr 6,000 kg*km/hr 3,000 kg*km/hr Total Mo (Mo of 2 cars combined): 6000 + 3000 = 9,000 kg*km/hr

5. The cars already collided. What is the total momentum after the crash? Mass: 300 kgMass: 250 kg Velocity: 15 km/hrVelocity: 18 km/hr Mo = 300 kg x 15 km/hr Mo = 250 kg x 18 km/hr 4,500 kg*km/hr 4,500 kg*km/hr lost 1500 kg*km/hr of Mo gained 1500 kg*km/hr of Mo Total Mo: 4500 + 4500 = 9,000 kg*km/hr

6. So was momentum conserved? 1. YES!! 2. Definition: In a collision, the TOTAL MOMENTUM of all the objects combined is the same before and after the “crash”. Whatever Mo one object loses the other one gains (just like energy!) 3. Momentum would not be conserved on in the real world because there would be friction. Momentum is conserved if there is no loss of mass or energy due to friction… Which never really happens (except when you are in happy, theoretical world).

7. Lets Discuss Collisions and Newton’s Third Law Car 1 hits car 2 Car 1 Car 2 Car 1 applies force to car 2 Car 2 applies equal force to car 1 Car 2 has + acceleration Car 1 has - acceleration

8. Lets Discuss Collisions and Energy Car 1 hits car 2 Car 1 transfers KE to car 2 Car 1 loses KE (slows down) Car 2 gains KE (speeds up)

9. Lets Discuss Collisions and Momentum Car 1 hits car 2 Car 1 transfers Mo to car 2 Car 1 loses Mo (slows down) Car 2 gains Mo (speeds up)

10. What is the Total Mo here? Mass: 400 kgMass: 300 kg Velocity: 35 km/hrVelocity: 40 km/hr Mo = 400 kg x 35 km/hr Mo = 300 kg x 40 km/hr 14,000 kg*km/hr 12,000 kg*km/hr Total Mo: 14000 - 12000 = 2,000 kg*km/hr to the right The cars are going in opposite directions, so subtract the Mo!

11. What is the total Mo after they collide? Momentum is conserved! So total Mo before = total Mo after So the total Mo is still 2,000 kg*km/hr (to the right)

12. @%$&*!!!

13. Mass = 10,000 kg Velocity = 5 m/s Mo = ? 10,000 kg x 5 m/s = 50,000 kg x m/s Before Collision

14. Mass = 5,000 kg Velocity = 0 m/s Mo = ? 0 kg x m/s Before Collision

15. Total Momentum + 50,000 kg x m/s Momentum is Conserved – this is the total momentum before and after the crash!

16. Mass = 10,000 kg Velocity = 0 m/s Mo = ? 0 kg*m/s After Collision: Total Mo = 50,000 Mass = 5,000 kg Mo = 50,000 kg*m/s The tank lost 50,000 kg*m/s of Mo – this Mo was transferred to the car The car gained 50,000 kg*m/s of Mo from the tank

17. Mass = 5,000 kg Mo = 50,000 kg x m/s V = ? V = Mo / Mass = 50,000 kg x m/s 5,000 kg V = 10 m/s What happened to the speed of the car? The speed of the car increased since it gained Mo! (remember the speed of the tank decreased)

18. Oh noooooooo I am in sooo muuuch trouble!

19. Mass = 5,000 kg Mass = 6,000 kg Velocity = 5 m/s Velocity = 0 m/s 5,000 kg x 5 m/s = 6,000 kg x 0 m/s = 25,000 kg x m/s 0 kg x m/s Total Mo Before Collision = ? 25,000 kg x m/s

20. What happened to the Mo and speed of the cars after the collision? The car lost Mo… this Mo was transferred to the cop car So the car lost speed The cop car gained Mo from the patriotic car So the cop car gained speed The total Mo remained the same

21. The cars have the same speed since they are moving together! Find the total Mo After Collision = 25,000 kg x m/s (Mo is conserved!) Find the combined Mass = 11,000 kg (6,000 +5,000) Then…

22. Velocity of the wreck: Since Mo = mass x velocity Velocity = Mo / mass 25,000 kg x m/s 11,000 kg 2.27 m/s

23. What is the momentum of each individual car after the crash? Mass = 5,000 kg Velocity = 2.27 m/s Mo = 11,363.64 kg*ms The car slowed down and lost 13636.36 kg*m/s of Mo. Mass = 6,000 kg Velocity = 2.27 m/s Mo = 13,636.36 kg*ms The car sped up and gained 13636.36 kg*m.s of Mo The total Mo = 25,000 kg*m/s The amount of Mo the patriotic car lost = the amount of Mo the cop car gained!