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Constant Speed & Acceleration Download Presentation ## Constant Speed & Acceleration

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1. Constant Speed & Acceleration

2. Lesson #1 Focus Question: Who is the fastest person in this room? • Mr. Moss • ? • ? • ?

3. Displacement Definition - change in position of an object How to measure – measuring tape, meter stick, laser range finder Units – meters also: cm, feet, miles, km d Start Finish Middle

4. Displacement

5. Time (t) Definition – the interval between events Measured – using clocks, atomic vibrations (really small), revolution of earth (big) Units – seconds also: (minutes, hours, years)

6. CPO Photogate & Timer Electronically Timed Volunteers

7. Velocity Definition – vector which shows the rate at which displacement changes with time Units – m/s or: mi/hr or km/hr Measured – same as speed Formula v =d t

8. Teacher Example C How long will it take for a car moving at 20 m/s to travel 1500 m?

9. Teacher Example B Calculate the time in standard units of a car that travels 65 m.p.h. for 34 km

10. Teacher Example B A man walks 10 m down the street then remembers he forgot his book at home. If his house is 100 m away from his destination and he takes 20 seconds to complete the trip what is his velocity?

11. Student Example C How far will a car traveling at 60 m/s go if it travels for 12 seconds?

12. Student Example C

13. Student Example B Calculate the distance in standard units of a car that travels 55 km/ hour for 35 minutes

14. Student Example B Calculate the average velocity of a car that moves 1800 m due east and then 2400 m due west in 125 seconds

15. Lesson #1: Rehash Focus Question: Who is the fastest person in this room? • Mr. C • ? • ? • ?

16. Clicker Quiz • Which of the following is NOT a unit of displacement? • mb) km c)sd) ft e)cm 2)Which of the following is the standard unit of velocity? • m/sb) s/mc)km/sd) mph e)ft 3) The formula v = d/t only works if • Constant velocity b) accelerated motion c) both 4) Displacement can be measured with a a) m/sb) s/mc)km/sd) mph e)ft 5) The photogate measures a) Displacement b) mass c) velocity d) time

17. Lesson #2 Focus Question: Why should you graph? • It looks better • You can look for trends • It allows you to predict the future • More than one of these

18. Displacement v. Time Graph

19. Graph Analysis • Always check the x and y axis • Find the slope value (What does y/x mean?) • Find the area value (What does x*y mean?)

20. Displacement v. Time Graph Can give you: • Change in position (displacement) after certain time • Time it takes to change positions • The average velocity (slope) for trip • The instantaneous velocity (with some Calculus) of a point

21. Teacher Example CDescribe in words the motion of each

22. Student Example CDescribe in words the motion of each

23. Teacher Example B • What will the motion be at 5 seconds?

24. Student Example B What is the time required for the object to reach 27 meters?

25. Lesson #2 - REHASH Focus Question: Why should you graph? • It looks better • You can look for trends • It allows you to predict the future • More than one of these

26. Clicker Quiz #2 • Why should you graph? • Predict the future b) look for trends c) display the date d) all of these 2) What is the slope of a displacement v. time graph? • Displacement b) time c) speed d) none of these 3) Which describes the motion of the graph? • Constant forward velocity • Constant backward velocity • Increasing positive velocity • Decreasing positive velocity

27. Lesson #3 Focus Question: What happens when you are traveling in a car moving the speed of light and you flip on the headlights? • They approach each other at the speed of light • They reach each other before they started • They approach each other less than the speed of light • They approach each other greater than the speed of light

28. Inertial Reference Frame Defined as the perspective from which a system is being observed Usually define up and right as positive and down and left as negative

29. Relative Motion

30. Example How fast does a plane travel relative to the ground if it is moving at 500 mph with a 20 mph wind behind it?

31. Teacher Example

32. Teacher Example A Car A is initially moving at 15 m/s in the right lane of the highway. Car B is moving at 22 m/s in the left lane. If Car B is initially behind Car A by 50 m then how long will it take Car B to pass Car A

33. Student Example How fast does a plane travel relative to the ground if it is moving at 250 mph with a 35 mph head wind?

34. Student Example A Car A is initially moving at 15 m/s in the left lane of the highway. Car B is moving at 22 m/s in the left lane moving the opposite direction. If they see each other at the top of their respective hills and it takes 10 seconds for them to pass then how far apart are the hills

35. Student Example A Two cars are separated by a distance of 1000 m. If both cars are travelling in the same direction then what is the velocity of Car B if Car B catches Car A after 50 seconds and Car A is known to be travelling 20 m/s

36. Einstein’s Relativity The fastest thing in the universe is light moving at 3.0 X10^8 m/s How fast to two light particles approach each other?

37. Relative Velocity Addition V’ = (v1 +/- v2) (1 +/- (v1v2/c^2))

38. Teacher Example How long will it take of two rockets travelling at 0.8c and 0.9c to pass each other if they one starts on Earth and the other at Mars (d = 8.8 X 10^10 m)?

39. Lesson #3 - Rehash Focus Question: What happens when you are traveling in a car moving the speed of light and you flip on the headlights? • They approach each other at the speed of light • They reach each other before they started • They approach each other less than the speed of light • They approach each other greater than the speed of light

40. Clicker Quiz #3 • A tail wind • Adds to your velocity b) subtracts from your velocity 2) Light is the fastest thing in the universe • True b) False 3) What is positive? • Up b) down c) right d) left e) more than one of these 4) Is there such thing as absolute motion? a) Yes b) No

41. Lecture #4: Acceleration & Graphs - Focus: Who in here can throw the fastest punch/throw a ball the fastest on Wii Sports • Mr. C • ? • ? • ?

42. Key Variables - Review Velocity – vector indicating the rate at which displacement changes with time. initial velocity (vi) – final velocity (vf) -

43. Key Variable - New Definition – vector indicating the rate of change in velocity. Measured – indirectly using velocity, distance and time or using an ACCELEROMETER Units – m/s^2 almost never ft/s^2

44. Key equation • Change in velocity a = Δv t

45. Teacher Example C Pick three ways you can safely accelerate a car and describe how each is classified as acceleration.

46. Teacher Example B Calculate the acceleration of a car that speeds up from rest to a velocity of 34 m/s east in 4 seconds

47. Teacher Example A Determine the time it takes for a car to accelerate from 20 to 60 mph if it can accelerate at 8.6 m/s2

48. Student Example C Pick an activity other than driving and show three ways that you accelerate in that activity and why you would accelerate.

49. Student Example B Calculate the final velocity of a car if it travels at 4 m/s west and accelerates at 1.2 m/s2 for 13 seconds