1. Momentum and change in momentum1

2. Question What would you rather get hit with?
A bowling Ball or a steel ball bearing? 2

3. Which would you rather get hit by?
1 bowling ball?
1 marble ? 3

4. On what information does your answer depend?4

5. DEFINITION OF MOMENTUM

6. Calculated value
Momentum is a calculated or derived value from information about forces and motion
Is not an intuitive value

7. Momentum “Pain upon impact” “Inertia in motion”
Quantity of motion found by multiplying an objects mass by its velocity
It is a vector value (Magnitude and Direction) 7

8. Units of momentum
Kg m/s 8

9. WHAT DOES HAVE MOMENTUM?

10. Who has momentum? 10

11. Examples of momentum Anything with mass that is in motion
Any object that is not moving has NO momentum

12. WHAT DOES NOT HAVE MOMENTUM?12

13. Examples of objects without momentum
Anything that has no velocity
A bus that is stopped has less momentum than a flea that is moving, but more inertia 13

14. What has more momentum?
The statue of liberty or a toddler walking at 0.5 m/s? 14

15. How can one change momentum?
Examples of objects changing their momentum 15

16. DETERMINATION OF AN OBJECTS MOMENTUM VALUE

17. Equation of momentum
P = m v 17

18. Momentum equation
P = m v P M V 18

19. Car Crashes
Why do some people survive and others do not? 19

20. Eggs and momentum

21. “Impulse”
CHANGE IN MOMENTUM

22. More examples of change in momentum22

23. Impulse The measure of a change in momentum
Any object that changes its mass or velocity over time changes its momentum
Any change in momentum requires a net force
Any application of a net force, results in a change of momentum of the object 23

24. Examples of net force changing momentum
Hockey stick on a puck
Wall on a car
Bat on a softball 24

25. WHAT CAR HAS THE GREATER IMPULSE?
The Red car that was going 45 mph stopped by the Brick Wall Or
The same red car that was going 45 mph and stopped by application of Brakes
WHAT CAR HAS THE GREATER IMPULSE?

26. Answer They have the same change in momentum
The car hitting a brick wall will have more force applied over a shorter time 26

27. Newton’s second law and ∆p
How does 2nd law relate to momentum?
Acceleration = the change in velocity over change in time a = ∆v / ∆t
Rewrite the 2nd law in terms of the change of momentum (This is how Newton presented the law) 27

28. Impulse equation
mΔv = Δp = Fnet ∆t
∆v = vf - vi 28

29. Which parts of the equation = the impulse?
Impulse = F ∆t
Impulse = m ∆v
Impulse = pf - pi 29

30. Important
For a given crash, the impulse is constant regardless of how the crash occurs
Impulse = mΔv 30

31. Time and force
The length of time it takes for the crash to be complete determines the amount of force applied during the crash
Seat belts
Foam padding
Air Bags
Crumple zones 31

32. Time and force
The longer the time allowed to exert a force, the less force is exerted 32

33. Again
What causes a change in the momentum? 33

34. Answer
An application of net force, producing a change in velocity (slowing down OR speeding up OR changing direction) 34

35. Change of momentum and Sports
Baseball/ softball
Golf 35

37. Catching a ball

38. Other examples
In cars, air bags, seat belts, padding on dashboard, steering wheel
In sports, catching a ball with a glove instead of a hand, bunting/home runs
In Dance, Gymnastics: Bending at the knees

39. To catch a tennis ball
Your hand must apply force to the ball to make it stop moving 39

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41. 41

42. 42

43. APPLICATIONS OF MOMENTUM

44. What determines if you live or die in an auto accident?44

45. Safety features 45

46. Safety features in cars that protect you during a crash
Seat belt
Air bags
Cushioned dashboard, steering weel
Padded headrest
Crumple zones 46

47. The way to survive an accident
Drive a car with:
Seat-belts
Air bag
Crumple zones
Soft dashboards/padded steering wheels
What benefit do these features provide? 47

48. What value do safety features extend?
The time of the crash
Impulse = Force x time 48

49. What value is decreased as a result of those safety features?
The amount of force needed to stop the car (and you) 49

50. The purpose of most safety features in a car is to lengthen the time of the accident
Air bags 50

51. Seat belts 51

52. Padding on dashboard, seats and steering wheel52

53. Crumple zones
It takes time for the parts of the car in the crumple zone to be crushed, less force applied to the passenger section 53

54. Any other means to protect the passengers during a collision?54

55. Other examples of change in momentum
Catching a Foul Ball
Being hit by a foul ball 55

56. Again
The main point of all safety devices in cars is to extend the time of the impact between human and car 56

57. Answer
The amount of force applied is related to the length of time required to bring the driver to a stop
The longer the time, the less force required 57