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Momentum and Impulse

Momentum and Impulse. Which would you rather get hit by?. 1 bowling ball?. 1 marble ?. On what information does your answer depend?. Car Crashes. Why do some people survive and others do not?. DEFINITION OF MOMENTUM. Momentum.

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Momentum and Impulse

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  1. Momentum and Impulse

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

  3. On what information does your answer depend?

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

  5. DEFINITION OF MOMENTUM

  6. Momentum A quantity of motion found by multiplying an object’s mass by its velocity Is a vector value (Magnitude and direction are important)

  7. Momentum “Pain upon impact” “Inertia in motion”

  8. Units of momentum Kg m/s

  9. What has momentum?

  10. What has more momentum? The statue of liberty or a SUV moving at 60 mph done the road?

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

  12. DETERMINATION OF AN OBJECTS MOMENTUM VALUE

  13. Equation of momentum P = m v

  14. How an object’s momentum changes is more useful than the momentum value at any point in time

  15. CHANGE IN MOMENTUM “Impulse”

  16. Impulse The measure of a change in momentum Symbol ∆p , units are the same Any object that changes its mass or velocity over time changes its momentum Any change in momentum requires a net force, acceleration Any application of a net force, results in a change of momentum of the object

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

  18. 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

  19. Answer They have the same change in momentum But the results of the change in momentum to each car is very different The car hitting a brick wall will have more force applied over a shorter time

  20. 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)

  21. The Impulse momentum theorem Fnet = ma = m ∆v / ∆t, rearrange to form theorem mΔv = Δp = Fnet ∆t ∆v = vf - vi

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

  23. Important For a given crash involving vehicles with identical masses, undergoing identical changes in velocity… the impulse is constant regardless of how the crash occurs Impulse = mΔv

  24. Time and force The length of time it takes for the crash to be complete determines the amount of force applied during the crash All of the measure found below extend the time of the crash, reducing applied force to passengers Seat belts Foam padding Air Bags Crumple zones

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

  26. Again What causes a change in the momentum?

  27. Change of momentum and Sports Baseball/ softball Golf

  28. Catching a ball

  29. To catch a ball Your hand must apply force to the ball to make it stop moving, The longer you can make the time spent applying force to the ball, the less force is needed

  30. APPLICATIONS OF MOMENTUM

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

  32. Safety features

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

  34. 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?

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

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

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

  38. Seat belts

  39. Padding on dashboard, seats and steering wheel

  40. 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

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

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

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

  44. 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

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