Momentum Unit

1. Momentum Unit 1. Momentum Mass vs Velocity Space Debris 2. Impulse Increasing momentum Decreasing momentum over a long time Decreasing momentum over a short time Rebounding (Bouncing) 3. Collisions/Explosions Conservation of p Elastic Inelastic Explosions

2. What is momentum? The concept of momentum is closely related to Newton’s Laws of Motion

3. 1. MOMENTUM The concept of momentum is closely related to Newton’s Laws of Motion Momentum – Inertia of a moving object

4. What is momentum? The concept of momentum is closely related to Newton’s Laws of Motion Momentum – Inertia of a moving object Momentum is a measure of how hard it is to Stop or turn a moving object

5. What is momentum? The concept of momentum is closely related to Newton’s Laws of Motion Momentum – Inertia of a moving object Momentum is a measure of how hard it is to Stop or turn a moving object It is related to both Mass and Velocity Only moving objects have momentum

6. What is momentum? The concept of momentum is closely related to Newton’s Laws of Motion Momentum – Inertia of a moving object Momentum is a measure of how hard it is to Stop or turn a moving object It is related to both Mass and Velocity Only moving objects have momentum What is the equation for momentum?

7. Calculating Momentum • For one object p = mv • For a system of multiple objects p = pi = mivi(total p is the sum of all individual p’s)

8. The unit for momentum p = mv

9. The unit for momentum p = mv Therefore, the unit for p = kg m/s Remember, momentum is a vector

10. Which has the most momentum?

11. Which has the most momentum? It Depends!

12. Which has the most momentum? M = 1000 kg, v = 1 m/s M = 10 g, v = 5 m/s

13. Which has the most momentum? Truck: Butterfly: M = 10 g, v = 3 m/s M = 1000 kg, v = 1 m/s p = mv p = mv p = (1000 kg) (1 m/s) p = (.01 kg) (3 m/s)

14. Which has the most momentum? Truck: Butterfly: M = 10 g, v = 3 m/s M = 1000 kg, v = 1 m/s p = mv P = mv P = (1000 kg) (1 m/s) p = (.01 kg) (3 m/s) P = 1000 kg m/s p = .03 kg m/s

15. Which has the most momentum? Truck: Butterfly: M = 10 g, v = 3 m/s M = 1000 kg, v = 1 m/s p = mv p = mv p = (1000 kg) (1 m/s) p = (.01 kg) (3 m/s) p = 1000 kg m/s p = .03 kg m/s How can the butterfly have the same momentum As the truck?

16. Which has the most momentum? Truck: Butterfly: M = 1000 kg, v = 1 m/s M = 10 g, v = p = 1000 kg m/s How can the butterfly have the same momentum As the truck? The mass of an object is usually constant, however, Velocity is easy to change.

17. Which has the most momentum? Truck: Butterfly: M = 1000 kg, v = 1 m/s M = 10 g, v = p = 1000 kg m/s The mass of an object is usually constant, however, Velocity is easy to change. Butterfly: p = mv 1000 kg m/s = (.01 kg) (Vb)

18. Which has the most momentum? Truck: Butterfly: M = 1000 kg, v = 1 m/s M = 10 g, v = p = 1000 kg m/s The mass of an object is usually constant, however, Velocity is easy to change. Butterfly: p = mv 1000 kg m/s = (.01kg) (Vb)  Vb = (1000 kg m/s)/(.01 kg) Vb = 100,000 m/s

19. Momentum Depends on mass AND velocity An object can have a large momentum if it has A large mass, even if it has a small velocity

20. Momentum Depends on mass AND velocity An object can have a large momentum if it has A large mass, even if it has a small velocity However, a small object can also have a large momentum if it has a large velocity

21. Grains of dust in space pose a bigproblem for satellites and spacecraft.

22. Grains of dust in space pose a bigproblem for satellites and spacecraft. Pieces of debris come from manmade objects, such as fuel drops, ice crystals, parts of spacecraft, or from natural things, such as stars and asteroids.

23. Pieces of debris come from manmade objects, such as fuel drops, ice crystals, parts of spacecraft, or from natural things, such as stars and asteroids. A dust particle can be .1 mm in size, and travel up to 158,000 miles per second

24. Pieces of debris come from manmade objects, such as fuel drops, ice crystals, parts of spacecraft, or from natural things, such as stars and asteroids. A dust particle can be .1 mm in size, and travel up to 158,000 miles per second

25. Pieces of debris come from manmade objects, such as fuel drops, ice crystals, parts of spacecraft, or from natural things, such as stars and asteroids. A dust particle can be .1 mm in size, and travel up to 158,000 miles per second

26. Space Debris Notice all the “junk” as they are looking for the MIR

27. ESA Space Debris

28. The Space ShuttleAlthough the fleet is retired, it is a good example of spacecraft window design Look closely at the windows…

30. The Space Shuttle

31. The Space Shuttle

32. The Space Shuttle Why were the windows reduced in size? Damage on heat shielding due to micro meteor impacts

33. The Space Shuttle Why were the windows reduced in size? This micro meteor traveled ¾ way through the glass before it stopped To protect against micro meteor impacts. One hole through the window can depressurize the entire cabin

34. The Space Shuttle The Space Shuttle reaches speeds of around 18,000 MPH. At these speeds, even foam insulation (with very little mass) also posed problems.

35. The Space Shuttle The Space Shuttle reaches speeds of around 18,000 MPH. At these speeds, even foam insulation (with very little mass) also posed problems.

36. The Space Shuttle The Space Shuttle reaches speeds of around 18,000 MPH. At these speeds, foam insulation (with very little mass) also posed problems. This will continue to be a problem with ANY vehicle that is designed to return to Earth. The point is, momentum depends on mass AND velocity

37. Momentum Review (with Bill Nye):

38. Momentum and rockets:

39. Sample Problem: • A 200 kilogram motorcycle is moving at a speed of 130 m/s. What is the momentum of the cycle?

40. Sample Problem: • A 200 kilogram motorcycle is moving at a speed of 130 m/s. What is the momentum of the cycle? • P = mv = (200 kg)(130 m/s) = 26000 kg m/s

41. Sample Problem: • A 200 kilogram motorcycle is moving at a speed of 130 m/s. What is the momentum of the cycle? • P = mv = (200 kg)(130 m/s) = 26000 kg m/s • A 60 kg person is riding the motorcycle at a speed of 130 m/s. What is the total momentum of the system?

42. Sample Problem: • Pcycle = 26000 kg m/s • A 60 kg person is riding the motorcycle at a speed of 130 m/s. What is the total momentum of the system? • Pperson = (60kg) (130 m/s) = 7800 kg m/s

43. Sample Problem: • Pcycle = 26000 kg m/s • A 60 kg person is riding the motorcycle at a speed of 130 m/s. What is the total momentum of the system? • Pperson = (60kg) (130 m/s) = 7800 kg m/s • ptotal = pcycle + pperson = 26000 kg m/s + 7800 kg m/s = 33800 kg m/s

44. 2. IMPULSE Often it is better to express momentum in relation to time. It is useful to know how much time it took to change or transfer momentum.

45. Lets play with some equations a little... p = mv and (what equation looks similar?)

46. Lets play with some equations a little... p = mv and F = ma (Newton’s 2nd law) These two equations look very similar. The only difference is the “v” and the “a”. What’s the difference between “v” and a?

47. Lets play with some equations a little... p = mv and F = ma (Newton’s 2nd law) These two equations look very similar. The only difference is the “v” and the “a”. What’s the difference between “v” and a? a = v/t  v = at

48. Lets play with some equations a little... p = mv and F = ma (Newton’s 2nd law) v = at All we have to do is multiply Force by time, and we get momentum… F t = mat

49. Lets play with some equations a little... p = mv and F = ma v = at All we have to do is multiply Force by time, and we get momentum… F t = mv

50. So if we apply force over a period of time, an object will accelerate (move). Any object that moves has momentum. F t = mv