1. Unit 3: Energy, Work and Power

2. Warm up

3. What is energy?

4. https://www.youtube.com/watch?v=CW0_S5YpYVo What is energy

5. What is energy?
Energy is the capacity for doing work. It may exist in potential, kinetic, thermal, electrical, chemical, nuclear and other forms.

7. The units for work are Joules (J) J= Nm
- A force that causes a displacement of an object does work on the object.
W = F∆x
The units for work are Joules (J)
J= Nm
Demo: drop a ball, use the scale

8. WORK
- Force component and displacement must be parallel.

9. How much work is done on a car pushed 15 m with a force of 80 N?

10. If 2.0 J of work is done by raising an apple using 8 N of force, what is the distance the apple was lifted?

11. Kinetic Energy (KE)

14. A 80 kg person runs at a constant velocity of 3. 5 m/s
A 80 kg person runs at a constant velocity of 3.5 m/s. What is their kinetic energy?

15. What is the velocity of a 0
What is the velocity of a kg baseball if its kinetic energy is 109 J?

16. 4.16 Joules = 1 calorie
1000 calories = I Calorie

17. A 65 kg person runs at a constant velocity of 4.0 m/s.
What is their kinetic energy?
How many calories (little c) are they burning? 4.16 Joules = 1 calorie

18. Potential Energy (PE)
- When an object has the 'potential' to move.

19. Potential Energy due to Gravity (PEg)
- PEg = mgh
- Gizmos and others might use a U to represent PEg

21. A 80 kg man stands at the top of a diving board the is 10 m height
A 80 kg man stands at the top of a diving board the is 10 m height. What is his potential energy?

24. KE Station Labs Three station attendance.
Calculate the KE of each object.

25. Day 2 Gizmos - Incline Planes

26. Day 3
Quiz 1

27. How would you find the potential energy of the red cup on top of the black book shelf?

28. 'Work' or 'No work‘?

29. Force vs. distance
The area under the graph is equal to the work done by the force.
Work is a scalar quantity.

31. Work-Kinetic energy theorem:
Wnet = ∆KE
Example: when you hit a nail with a hammer, part of the energy is used to drive the nail into the wall but part of the energy goes into warming the hammer and the nail and some energy goes into creating the sound.

32. On a frozen pond, Rachael pushes a 10 kg sled that is at rest
On a frozen pond, Rachael pushes a 10 kg sled that is at rest. The sled reaches a velocity of 2.2 m/s. Assume you can ignore friction. How much work was done by Rachael?

34. Break

35. Potential energy (PEs) and the force (Fs) of a spring
K is the spring constant.
Phet spring

36. Find Fspring Find PEspring

37. A spring with a constant of 3 N/m is compressed 24 cm.
What is its potential energy?
What force was required to compress the spring?

38. Find x

39. Find x

40. https://www.youtube.com/watch?v=wGIZKETKKdw slinky drop

42. Elastic energy is spring energy
Elastic energy is spring energy. Any object that compresses and springs back into shape.
Human slingshot
Elastic golf ball

43. PEg and PEspring Activity
How comfortable are you with Potential Energy?
Who will hold the whiteboard?
Who will keep track of time?

44. PEg and PEspring Activity
Stations:
Find the spring constant for the force meters.
Find PEg for the 3 object on the shelf.
Find Fspring Find PEspring for the following picture.

45. Day 4
Quiz 2

47. Mechanical energy is KE and PE combined.
Mechanical energy is usually conserved.
Parkour

48. Pendulum and mechanical energy
Phet pendulum

49. ∆h = is 0.30 m.
Find the velocity of the ball at the bottom of the pendulum.

50. A 75 kg diver drops from a board 10. 0 m above the water
A 75 kg diver drops from a board 10.0 m above the water. Find the diver's velocity just before striking the water.

51. You use a water balloon launcher to launch a 0. 5 kg apple
You use a water balloon launcher to launch a 0.5 kg apple. You stretch the launcher 1 m. If the launcher has a spring constant of 75 N/m, what is the velocity of the apple once it is released?

52. A bird is flying with a speed of 18
A bird is flying with a speed of 18.0 m/s over water when it accidentally drops a 2.00 kg fish. If the altitude of the bird is 5.40 m and we ignore friction, what is the velocity of the fish when it hits the water?

53. Energy is always conserved.
Mechanical energy is NOT always conserved.
Energy can be stored or transferred.
Energy can NEVER be destroyed.
Sometime it is transferred into sound or heat.

54. Break

55. https://www.youtube.com/watch?v=omwX3cK3G4k fight science

56. How long does it take a 19 kW steam engine to do 6.8x107 J of work?

57. A 1000 kg elevator can carry a maximum load of 800 kg
A 1000 kg elevator can carry a maximum load of 800 kg. A constant frictional force of 800 N slows the elevators motion upwards. What minimum power, in Watts, must the motor deliver to lift the fully loaded elevator at a constant speed of 3.00 m/s?

58. A 193 kg curtain needs to be raised 7
A 193 kg curtain needs to be raised 7.5 m, at a constant speed, in as close to 5.0 s as possible. You can choose from 3 different motors with a power rating of 1.0 kW, 3.5 kW and 5.5 kW. Which motor do you chose?

59. A 1. 5x103 kg car accelerates uniformly from rest to 10. 0 m/s in 3
A 1.5x103 kg car accelerates uniformly from rest to 10.0 m/s in 3.0 s. What is the work done on the car in this time interval? What is the power delivered by the engine in this time interval.

60. Conservation of Mechanical Energy and Power WS.

61. Day 5

62. Roller coaster
roller coaster PE and KE

65. Almost everything, moving on earth, experiences some type of friction.
This means Mechanical Energy is almost always lost to friction.

66. Gizmos - Roller Coaster

67. Day 6
Quiz 3

68. Conservation of Mechanical Energy station lab.

69. Roller Coaster Gallery Walk

70. Roller Coaster Gallery Walk
You will evaluate the other roller coasters in you audience category.
The pink sticky notes are for things you like.
The yellow sticky notes are for things you would change.
You must decide between the two of you what comments to leave.
I will tell you when to rotate to the next roller coaster category.
We will return to class an vote on your favorite roller coasters. Your vote will be individual.
You will also complete some reflection questions in the Google form.