1. Energy is the ability to do work or cause change. Work is done when a force causes an object to move, and is measured in Joules. 2. Kinetic energy depends on an object's mass and speed, and is calculated as KE=1/2mv^2. Potential energy depends on an object's mass and height, and is calculated as PE=mgh. 3. Mechanical energy is the total of an object's kinetic and potential energies, or ME=KE+PE. As an object moves, its kinetic energy increases as its potential energy decreases, keeping the total mechanical energy constant.

1. Warm up… How are energy and work related?

2. ENERGY Chapter 5 Section 1

3. Energy is the ability to do work Work is the transfer of energy Force moves an object Measured in Joules (J) What are some things that make a job feel like more work? Energy… Force

4. How are energy and work being done during this tennis match?

5. How are energy and work being done during a golf tournament?

6. Energy of MOTION Depends on speed and mass KE = mv2 2 LOOK at the formula… Which has a greater effect on KE, mass or speed? Why/how do you know? Kinetic Energy

7. INDEX CARD ENERGY UNIT FORMULAS… KE = mv2 2

8. Which has more KE-the red car or green car? Explain.

9. Which has more KE-the red car or truck? Explain.

10. A snail with a mass of 5 g traveling at 0.014 m/s has a KE of 0.00000048 J! An 18-wheel truck traveling at 44 mi/h has a KE of 2,200 J! Weird Science...

11. Provide a caption for your work/energy picture Label any area where work is being done (you should have at least 2 places where you have shown some work) Put your name and class period on the back of your illustration

12. On the back of your paper, please explain the following in a short paragraph: -Energy -Work -How your picture demonstrates these 2 ideas

13. Warm up… What is your hypothesis for the rubber band racers? What is the independent variable? The dependent?

14. Rubber Band Racers… Build your car quickly; divide the jobs and work as a team Begin with 1 energy unit (1 winding) and run 3 trials for each number of windings; collect data Average the data for each energy unit Graph the average data for distance vs the energy units YOU MUST MEASURE DISTANCE IN METRIC

15. Warm up… Was your hypothesis for your racer correct? Why? What is a good title for the graph you will create with this data?

16. Warm up… What are the 2 factors that determine the KE of an object?

17. KE FACTORS DEMO… Copy the chart below into your notes. Using the setup described on the paper at your table, launch the lid with the discs. Record your data.

18. Quickly graph your data. Answer the 3 questions below: What was the trend you observed as you increased the # of washers you launched? Using your graph, what would the distance have been for 2 washers? What is the independent variable in this quick demo? Why/Explain.

19. KE PROBLEMS… 1. What is the kinetic energy of a car that has a mass of 1,200 kg and is moving at a speed of 20 m/s? 2. What is the kinetic energy of a car that has a mass of 2,400 kg and is moving at a speed of 20 m/s? 3. How does the kinetic energy of the 2 cars above compare? What do you notice?

20. Cool down… What are the 2 factors that determine the KE of an object? What is the formula for KE? Which factor has a greater impact on KE?

21. Warm up… What are the 2 factors that determine the KE of an object? What is the formula for KE? Which factor has a greater impact on KE?

22. Energy of POSITION or SHAPE Depends on weight and height The amount of work done to get object in that position. GPE = weight x height What’s the difference between weight & mass? Potential Energy

23. INDEX CARD ENERGY UNIT FORMULAS… KE = mv2 2 GPE = weight x height

24. Diver A 450 N Diver B 500 N Does Diver A or B have more GPE? Which Diver did more work?

25. Does Diver C or D have more GPE? Which Diver did more work? Diver C 550 N Diver D 550 N

26. Diver C 550 N Diver A 450 N Diver B 500 N Diver D 550 N Which Diver did the most work?

27. GPE PROBLEMS… 1. What is the gravitational potential energy of a book with a weight of 13 N at a height of 1.5 m off the ground? 2. What is the gravitational potential energy of a cat that weighs 40 N standing on a table that is 0.8 m above the ground?

28. The sum of the kinetic and potential energy. ME = KE + PE Mechanical Energy

29. INDEX CARD ENERGY UNIT FORMULAS… KE = mv2 2 GPE = weight x height ME = KE + PE

30. Weight = 200 N Mass = 20 kg What is GPE of the car? What is KE of the car? Speed = 0 m/s Height = 5 m

31. Weight = 200 N Mass = 20 kg GPE = Wt * Ht = 200 * 5 GPE = 1,000 J KE = m * v2 / 2 = 20 *02 / 2 KE = 0 J Speed = 0 m/s Height = 5 m

32. Warm up… What is the difference between GPE and KE? Why do we use mass for KE and weight for GPE?

33. Weight = 200 N Mass = 20 kg What is the ME for this system? Speed = 0 m/s Height = 5 m

34. Weight = 200 N Mass = 20 kg ME = KE + PE ME = 0J + 1,000J ME = 1,000J Speed = 0 m/s Height = 5 m

35. Weight = 200 N Mass = 20 kg What is GPE of the car now? What is KE of the car now? Height = 5 m Speed = 10 m/s

36. Weight = 200 N Mass = 20 kg GPE = Wt * Ht = 200 * 0 GPE = 0 J KE = m * v2 / 2 = 20 *102 / 2 KE = 1,000 J Height = 5 m Speed = 10 m/s

37. Warm up… What kind of energy is found in a stretched rubber band? Explain. What kind of energy in found in a rubber band that has been released? Explain.

38. Warm up… On a ramp, where would you find the most potential energy? Where would you find the most kinetic energy?

39. Weight = 200 N Mass = 20 kg What is the ME for this system? Height = 5 m Speed = 10 m/s

40. Weight = 200 N Mass = 20 kg ME = KE + PE ME = 1,000J + 0J ME = 1,000J Height = 5 m Speed = 10 m/s

41. GPE = 1,000J KE = 0J

47. GPE = 0J KE = 1,000J

48. What’s happening to the GPE as he rolls down the hill? Height decreases so GPE decreases

49. What’s happening to the KE as he rolls down the hill? Speed increases so KE increases

50. If the ME for this system is 1,000J, what would expect the GPE and KE to be at the half way point? ME = 500J + 500J

51. More KE, less GPE

52. Almost all KE now

53. GPE = 0J KE = 1,000J 850J Wait a minute, Mrs. Lock! When we tested this in the lab, the KE at the bottom was LESS than the GPE at the top. WHY??? Where did the energy go?

54. GPE = 0J KE = 1,000J 850J Some energy was changed into heat and sound as the car wheels rubbed against the ramp. ME = KE + PE + friction!

55. Warm up… How does a pendulum show KE and GPE?

56. Warm up… What is the GPE at Point A? What is the ME for the picture? What is the GPE at Point B? What is the approximate KE at Point B? 100 N 20 M 10 M

57. Warm up… How does a pendulum show energy conversions? What is the law of Conservation of Energy?

58. A Pendulum Experiment Info: We want to see what affects the time a pendulum takes to swing. Time period is the time for a full swing (forward and backward). Question: How does length of the pendulum affect its time period?

59. Question: How does length of the pendulum affect its time period? Write your hypothesis using the question above. Remember it MUST be an “If…then…” statement. Use an independent and a dependent variable

60. Data: Copy the chart below:

61. Steps: 1. Measure the length of string 2. Measure the time for 20 full swings 3. Divide by 20 to find the time for 1 swing. 4. Repeat this for 9 additional string lengths 5. Graph the data (independent variable on the x-axis, dependent on the y-axis)

62. Warm up… What is happening to energy at the top of a jump on a trampoline? At the bottom?

64. Pop Quiz Wt=50N A. B. C. What is the KE at point A? What is the PE at point A? What is the ME at point A? What is the PE at point B? Use ME(and PE) to find the KE at point C. Show work on back Put answers on front