1. On the highway of life, are you the bug or the windshield?

2. Bug hits windshield

3. Windshield hits bug

4. The force on each is… WHICH? a)Less b)More c)The same

5. The force on each is… c) The same! Newton’s third law You can only exert back as much force as is exerted on you.

6. The time of impact is… a)Less b)More c)The same

7. The time of impact is… The same! It would be impossible for the bug to hit the windshield for 2 seconds while the windshield hits the bug for 3 seconds.

8. The IMPULSE is… a)Less b)More c)The same Impulse is Force x time!

9. The IMPULSE is… c) The same! If Force is the same, and time is the same, Ft has to be the same Impulse is Force x time!

10. The change of velocity on each is… a)The same for bug and car b)Very Different for bug and car

11. The change of velocity on each is… b) Very Different! The car, hardly noticeable. The bug, VERY noticeable. The bug slows down, stops and reverses direction.

12. The momentum before and after… a)The same. b)Different.

13. The total momentum before and after… a)The same! Momentum is conserved in a collision.

14. The CHANGE in momentum of car, and the change in momentum of bug… a)Larger for the bug b)Larger for the car c)The same d)No way to tell

15. The CHANGE in momentum of car, and the change in momentum of bug… c) The same! Impulse = Change in p

16. What about a BIGGER BUG?

17. The force on each is… The same- Newton’s third law You can only exert back as much force as is exerted on you.

18. The time of impact is… The same- It would be impossible for the bug to hit the windshield for 2 seconds while the windshield hits the bug for 3 seconds.

19. The change of velocity on each is… Slightly Different – The car, slows down noticeably. The bug slows down, stops and reverses direction.

20. So why does the bug go splat, but a windshield doesn’t?

21. Its only a Small force when a bug hits the windshield. It only takes a small force to kill a bug. That same size force won’t hurt the windshield.

22. The differences - the size of the force, impulse and momentum. The smaller the bug, the less force, impulse, change in momentum, the bigger the bug the more of each.

23. What if the bug is the same mass and same speed as a car?

24. They stop!

25. (mv) car = -(mv) bug Equal quantities in OPPOSITE directions. Bug’s v will be negative. (mv) car + (mv) bug = 0

26. Momentum symbol is p (Why p?) (Why p?) p BEFORE collision = p AFTER collision SO, the basic format for every momentum problem elastic collision: m c v c + m b v b = m c ’v c ’ + m b ’v b ’ OR: (m c v c ) i + (m b v b ) i = (m c v c ) f + (m b v b ) f

27. Objects in an ELASTIC collision…bounce off.

28. Momentum symbol is p (Why p?) (Why p?) p BEFORE collision = p AFTER collision SO, the basic format for every momentum problem inelastic collision: m c v c + m b v b = m c ’v c ’ + m b ’v b ’ OR: (m c v c ) i + (m b v b ) i = (m c v c ) f + (m b v b ) f

29. Objects in an INELASTIC collision…stick together.

30. For our car and bug, do they have an ELASTIC, or INELASTIC collision?

31. INELASTIC!! They stick together.

32. Here are some approximate numbers: Car mass 1500 kg Car speed 60 mph = 33m/s Bug mass 1 g = 0.001 kg Bug speed bug speed 10 mph = 7 m/s QUESTION 1: What is the VELOCITY of the bug and car smashed together in the inelastic collision AFTER the collision? QUESTION 2: a) What is the CHANGE in velocity of car? b) And bug?

33. PLEASE try to solve! BEFORE you go to the next slide!! What formula will you use? Please write out your work!

34. (1500kg) (33m/s) + (0.001kg) (-7m/s) = (1500kg + 0.001kg)v 49500kg ms/+ -0.007kgm/s = 1500.001kg(v) 49499.993kg m/s = 1500.001kg(v) 32.99m/s = v

35. So the car’s velocity changes from 33m/s to 32.99m/s, while the bug changes from -1m/s to 32.99m/s.