1. 1/4 Bell Work A survey of 50 editors showed that 20 could write with their left hand and 10 could write with either hand.  How many could write with their right hand?

2. 1/4 Schedule  Notes Ch 13.1 “Work, Power, and Machines”  Simple Machines Station 1  Make sure surface is level.  Keep packet for later.  Start CR 13.1 Notes: 1.Ch 13 “Work” packet – TBA 2.Concept CR 13.1 due WED

3. Unit: Work, Energy, and Heat Ch 13-14 Objectives: 1. Describe how changes in form relate to conservation of energy. 2. Calculate work, energy, heat and temperature. 3. Explain transfer of energy and heat.

4. Ch 13.1 “Work, Power, and Machines” Objectives: 〉 Calculate work. 〉 Describe the relationship between work and power. 〉 Explain how machines make work easier.

5. Work, work, work? 1. Which of the following is an example of work: bowling or reading? 2. Are the following work? a. A man pushes against a brick wall, which doesn ’ t move. Is this an example of work? b. A student carries her books to class. Is this an example of work?

6. Work, work, work? c. A woman raises and lowers dumbbells at the gym. Is this an example of work? d. A book falls off a table and lands on the floor. Is this an example of work?

7. What Is Work? Work Definition  T he transfer of energy to an object by a force that causes the object to move in the direction of the force  Work is zero when an object is not moving.  Work is measured in joules (J): 1 N m = 1 J = 1 kg m 2 /s 2

8. What Is Work? Work Definition  Calculated by multiplying the force by the distance over which the force is applied.  work = force x distance, or W = Fd  The force must be applied in the direction of the object ’ s motion.

9. Math Skills Work Imagine a father playing with his daughter by lifting her repeatedly in the air. How much work does he do with each lift if he lifts her 2.0 m and exerts an average force of 190 N? 1. List the given and unknown values. Given: force, F = 190 N distance, d = 2.0 m Unknown: work, W = ? J

10. Math Skills, continued 2. Write the equation for work. work = force  distance W = f  d 3. Insert the known values into the equation, and solve. W = 190 N  2.0 m = 380 Nm W = 380 J

11. Power Work vs Power 〉 Power is the rate at which work is done, or how much work is done in a given amount of time.  Power is measured in watts (W): 1 W = 1 J/s

12. Math Skills Power Lifting an elevator 18 m takes 100 kJ. If doing it takes 20 s, what is the average power of the elevator during the process? 1. List the given and unknown values. Given: work, W = 100 kJ = 1  10 5 J time, t = 20 s Distance is not needed. Unknown: power, P = ? W

13. Math Skills, continued 3. Insert the known values into the equation, and solve. 2. Write the equation for power.

14. Knowledge is knowing a tomato is a fruit. Wisdom is not putting it in a fruit salad. - Peter Kay, English comedian  What do you think Peter Kay means? 1/5 Bell Work

15. 1/5 Schedule  Notes Ch 13.1 “Work, Power, and Machines” – 13.2 “Simple Machines”  Simple Machines Station 2  Keep packet for later.  CR 13.1-13.2 Notes: 1.Ch 13 “Work” packet – TBA 2.Concept CR 13.1 due WED

16. Machines and Mechanical Advantage Machines make work easier.  changing the size of an input force, the direction of the force, or both.

17. Machines and Mechanical Advantage  Look at the sodas containers below.  What tools could you use?  Why do these tools make it easier to open the sodas?

18. Machines and Mechanical Advantage Mechanical advantage is a useful ratio.  mechanical advantage: expresses how much machines multiply force or distance  AKA: How much easier is the task?

19. Math Skills Mechanical Advantage Calculate the mechanical advantage of a ramp that is 5.0 m long and 1.5 m high. 1. List the given and unknown values. Given: input distance = 5.0 m output distance = 1.5 m Unknown: mechanical advantage = ?

20. Math Skills, continued 2. Write the equation for mechanical advantage. We need only the distance part of the full equation: 3. Insert the known values into the equation, and solve. mechanical advantage =

21. Ch 13.2 “Simple Machines” Objectives: 〉 Identify the 6 types of simple machines and give examples. 〉 Describe and locate the two different parts of all levers. 〉 Explain how using an inclined plane changes the amount of force needed to move an object.

22. Open Door, Open Mind Doors are actually machines, specifically levers. When you exert a force on it (input), that force is exerted along the entire door (output).

23. Open Door, Open Mind 1. There is always one point along the lever that remains still while the rest moves. This point is the fulcrum. Where is the fulcrum of a door? 2. You can push at any point along the width of a door and it will open. Which position requires the least force: near the hinges, in the middle, or the side farthest from the hinges? (Hint: Which feels easiest?) 3. If you are trying to prop the door open with a small, light doorstop, where would you place the doorstop?

24. What Are Simple Machines? 6 Simple Machines Types: 〉 Lever 〉 Pulley 〉 Wheel and axle 〉 Inclined plane 〉 Wedge 〉 Screw.

25. What Are Simple Machines? Simple machines are divided into two families: the lever family and inclined plane family. Lever family:  simple lever  pulley  wheel and axle Inclined plane family: –simple inclined plane –wedge –screw

26. The Lever Family Levers  Parts: 1. Rigid arm 2. Pivot point/Fulcrum  Three classes  1 st : Fulcrum between input and output force, EX see saw  2 nd : Fulcrum at end, smaller input = bigger output, EX wheelbarrow  multiply force  3 rd : Fulcrum at end, big input = smaller output, EX muscles  multiply distance

27. The Lever Family, continued Force applied to end. Force applied middle.. Fulcrum located in middle.

28. The Lever Family, continued Pulleys are modified levers.  The middle of a pulley is like the fulcrum.  The rest of the pulley behaves like a first-class lever.  A wheel and axle is a lever or pulley connected to a shaft.  Screwdrivers and cranks are common wheel-and-axel machines.

29. The Mechanical Advantage of Pulleys

30. 5 th Hr Welcome Back!! Please find your seat. Stand by the back counter if your name is not there. DeJuan Q.Melanie K. Ana C. Charles D.Kiara G. Lacey W. Ryan T.Jemila F. Tanisha N.

31. 6 th Hr Welcome Back!! Please find your new seat. Stand by the back counter if your name is not there. Natasha C.Teesha R. Travis L.Marvelous R Savannah T.Preston K. Austin M.Kasey D.

32. 1/6 Bell Work Pete Platform and Gary Gladhand met at a club to discuss the overthrow of their party leader. They each ordered Pepsi on the rocks. Gary downed his and ordered another. He gulped down the second, but decided to wait on the third. Meanwhile, Pete, who was sipping his drink suddenly dropped over dead. Both men were set up for assassination.  Where was the poison? Why did Gary survive, but Pete died?

33. 1/6 Schedule  Notes Ch 13.2 “Simple Machines”  Simple Machines Station 3  Write procedure 3a  Keep packet  CR 13.1-13.2 Notes: 1.Ch 13 “Work” packet – TBA 2.Concept CR 13.1-13.2 THURSDAY

34. The Inclined Plane Family Incline planes and Force 〉 Pushing an object up an inclined plane requires less input force than lifting the same object does.

35. The Inclined Plane Family  A wedge is a modified inclined plane.  A screw is an inclined plane wrapped around a cylinder.

36. Compound Machines Simple + Simple = Compound Machine 〉 EX: scissors use two first-class levers joined at a common fulcrum; each lever arm has a wedge that cuts into the paper.

37. Compound Machines  More Examples and Results Fulcrum-> Load-> Effort Magnifies force to crack nut Fulcrum-> Effort-> Load Magnifies movement, low force

38. 1/7 Bell Work If a block weighs 8 kg plus half a block, how much does a block and a half weigh?

39. 1/7 Schedule  Notes Ch 13.3 “What is Energy?”  Simple Machines Lab 3 and 5  Cross off Station 4  Station 5: draw and label machines  Turn in  Practice with Simple Machines at  http://www.msichicago.org/play/simplemachines/ Notes: 1.Ch 13 “Work” packet – MONDAY 2.Simple Machines Lab – FRIDAY

40. Ch 13.3 “What is Energy?” Objectives: 〉 Describe the relationship between work and energy. 〉 Explain the relationship between potential and kinetic energy. 〉 Define nonmechanical energy.

41. Energy Transfer Energy is always conserved. It just changes from one form to another. For example, sunlight is the ultimate source of energy on Earth. Look at the illustration below, and identify the types of energy involved.

42. Energy Transfer 1. How does sunlight provide the energy the girl needs to swing the bat? ( Hint: What do you need to have energy?) 2. When the girl hits the ball, she exerts a force on it. Does she do work on the ball in the scientific sense of the term? Explain your answer. 3. After the girl hits the ball, the ball moves very fast and has energy. When the ball hits the fielder ’ s glove, it stops moving. What happens to the energy the ball once had? ( Hint: What do you hear and feel as you catch the ball?)

43. Energy and Work Relating Energy and Work 〉 Whenever work is done, energy is transformed or transferred. 〉 Energy : the capacity to do work  Energy is also measured in joules (J).

44. Potential Energy Potential energy: the energy that an object has because of the position, shape, or condition of the object 〉 Potential energy ( PE ) is sometimes called energy of position because it results from the relative positions of objects in a system.

45. Potential Energy, continued Major Types of Potential Energy  Elastic Potential Energy: any object that is stretched or compressed to increase or decrease the distance between its parts.  EX: stretched bungee cords, compressed springs  Gravitational Potential Energy: any system of two or more objects separated by a vertical distance.  EX: a roller coaster at the top of a hill, skydiving

46. Potential Energy, continued  Gravitational potential energy depends on both mass and height.  grav. PE = mass  free-fall acceleration  height, or PE = mgh  The height can be relative…. “with respect to _________”  EX floor, ceiling, Earth, cliff…

47. Math Skills Gravitational Potential Energy A 65 kg rock climber ascends a cliff. What is the climber ’ s gravitational potential energy at a point 35 m above the base of the cliff? 1. List the given and unknown values. Given: mass, m = 65 kg height, h = 35 m free-fall acceleration, g = 9.8 m/s 2 Unknown: gravitational potential energy, PE = ? J

48. Math Skills, continued 2. Write the equation for gravitational potential energy. PE = mgh 3. Insert the known values into the equation, and solve. PE = (65 kg)(9.8 m/s 2 )(35 m) PE = 2.2  10 4 kgm 2 /s 2 PE = 2.2  10 4 J

49. 1/8 Bell Work Approximately how far would a tire with a 2 foot diameter roll in 700 revolutions? Hint: Use circle equations in planner.

50. 1/8 Schedule  Notes Ch 13.3 “What is Energy?”  Simple Machines Lab 3 and 5  Cross off Station 4  Station 5: draw and label machines  Turn in  Practice with Simple Machines at  http://www.msichicago.org/play/simplemachines/ Notes: 1.Ch 13 “Work” packet – MONDAY 2.Simple Machines Lab – FRIDAY

51. 1/8 Schedule  Finish notes Ch 13.3 “What is Energy?”  Turn in Simple Machines Lab  Kinetic and Potential Energy Practice Wksht due MONDAY Notes: 1.Simple Machines Lab – TODAY 2.Ch 13 “Work” packet – MONDAY 3.Kinetic and Potential Energy Prac Wksht due MONDAY

52. More Potential Energy Problems Put these in your notebook. PE = mgh 1. The world record for pole vaulting is 6.15 m. If the pole vaulter’s gravitational potential is 4,942 J, what is his mass? 2. What is the gravitational potential energy associated with a 75 kg tourist at the top floor of the Sears Tower in Chicago, with respect to the street 436 m below?

53. Kinetic Energy Kinetic Energy Factors 〉 Kinetic energy depends on both the mass and the speed of an object.  KE = ½  mass  speed squared, or KE= ½mv 2  Does kinetic energy depend more on mass or velocity?

54. Kinetic Energy, continued Atoms and molecules have kinetic energy.

55. Math Skills Kinetic Energy What is the kinetic energy of a 44 kg cheetah running at 31 m/s? 1. List the given and unknown values. Given: mass, m = 44 kg speed, v = 31 m/s Unknown: kinetic energy, KE = ? J

56. Math Skills, continued 2. Write the equation for kinetic energy. 3. Insert the known values into the equation, and solve. KE = ½ (44 kg)(31 m/s) 2 = 2.1 × 10 4 kgm 2 /s 2 KE = 2.1 × 10 4 J

57. More Kinetic Energy Problems KE= ½mv 2 1. A cheetah can run briefly with a speed of 31 m/s. Suppose a cheetah with a mass of 47 kg runs at this speed. What is the cheetah’s kinetic energy? 2. The kinetic energy of a golf ball is measured to be 143.3 J. If the golf ball has a mass of about 47 g, what is its speed? (Remember to convert g to kg.)

58. 1/11 Bell Work  Create an equation whose answer is 11 that also includes fractions. EX: (24/3) + 3 = 11

59. 1/11 Schedule  Finish notes Ch 13.3- start 13.4 “Converting”  Work Time  Kinetic and Potential Energy Practice Wksht due TODAY  Con Rev Ch 14 now due TUESDAY Notes: 1.Simple Machines Lab – LATE 2.Kinetic and Potential Energy Prac Wksht due TODAY 3.Ch 13 “Work” packet – TUESDAY Starting Solar Oven Project! Bring in cardboard, foil, newspaper, etc. for WEDNESDAY

60. Other Forms of Energy Nonmechanical energy 〉 Energy at the level of the atom.  mechanical energy: the amount of work an object can do because of the object ’ s kinetic and potential energies  In most cases, nonmechanical forms of energy are just special forms of either kinetic or potential energy.

61. Other Forms of Energy, continued Chemical reactions involve potential energy.  The amount of chemical energy associated with a substance depends in part on the relative positions of the atoms it contains. Living things get energy from the sun.  Plants use photosynthesis to turn the energy in sunlight into chemical energy. The sun gets energy from nuclear reactions.  The sun is fueled by nuclear fusion reactions in its core. Fusion

62. Other Forms of Energy, continued  Energy field storage.  Electric fields result in electrical energy based on the location of charged particles.  When electrons move from an area of higher electric potential to an area of lower electric potential, they gain energy. Electric field lines

63. Other Forms of Energy, continued  Light carries energy across empty space.  Light energy travels from the sun to Earth in the form of electromagnetic waves.  Electromagnetic waves are made of electric and magnetic fields.

64. 1/12 Bell Work  If there are 6.02 x 10 23 atoms in a mole, how many moles are there in 18 x 10 23 atoms of iron?

65. 1/12 Schedule  Finish notes 13.4 “Converting”  Work Time  Kinetic and Potential Energy Practice Wksht LATE  Con Rev Ch 14 now due TODAY Notes: 1.Simple Machines Lab – LATE 2.Kinetic and Potential Energy Prac Wksht LATE 3.Ch 13 “Work” packet – TODAY Starting Solar Oven Project! Bring in cardboard, foil, newspaper, etc. for WEDNESDAY

66. Ch 13.4 “Conservation of Energy” Objectives 〉 Describe how energy changes. 〉 Define and apply the Law of Conservation of Energy.

67. Converting Energy You and your sled have gravitational potential energy when you get to the top of a snowy hill. Then you slide down, speeding up as you go.

68. Converting Energy 1. When does the sled have the most potential energy? Least potential energy? 2. Where does the sled have the most and least kinetic energy? 3. After the sled reaches the bottom of the hill, it coasts across level ground and eventually stops. What happened to the energy the sled had?

69. Energy Transformations Potential can become kinetic energy.  EX: As a roller coaster car goes down a hill, PE changes to KE. Kinetic can become potential energy.  Example: The KE of a roller coaster car at the bottom of a hill can do work to carry it up another hill.

70. The Law of Conservation of Energy Law of Conservation of Energy: Saving/Keeping Energy  Energy cannot be created or destroyed.  Total amount of energy in the universe never changes.  Energy may change from one form to another.  Light, heat, sound, …

71. The Law of Conservation of Energy Energy does not appear or disappear.  Whenever total energy in a system increases, it enters the system from an external source. Thermodynamics describes energy conservation.  1 st Law of Thermodynamics = A net change in energy equals the energy transferred as work and as heat.  aka “No free lunch.”

72. The Law of Conservation of Energy Different Types of Systems open system : energy and matter are exchanged with the surroundings closed system : energy but not matter is exchanged isolated system : neither energy nor matter is exchanged  Most real-world systems are open.

73. Connecting Potential and Kinetic Energy  Assuming that energy is conserved and there is no friction, at the bottom of the hill the cart’s potential energy is completely converted to kinetic energy. Use the formulas to calculate the cart’s speed at the bottom of the hill.  What are the equations for potential and kinetic energy? m ? m

74. Review Conservation of Energy If energy was conserved E p = E k. Otherwise it was “lost”. 1. Use the car’s potential energy at the top of the ramp. E p = mgh 2. It should equal the car’s kinetic energy when it hit. E k = ½*mv 2 3. Solve for v.

75. Stop Notes  Stop here for today.

76. Efficiency of Machines Not all work by a machine is useful.  because of friction, work output < work input  Efficiency is the ratio of useful work out to work in.

77. Math Skills Efficiency A sailor uses a rope and an old, squeaky pulley to raise a sail that weighs 140 N. He finds that he must do 180 J of work on the rope to raise the sail by 1 m. (He does 140 J of work on the sail.) What is the efficiency of the pulley? Express your answer as a percentage. 1. List the given and unknown values. Given: work input = 180 J useful work output = 140 J Unknown: efficiency = ? %

78. Math Skills, continued 2. Write the equation for efficiency. 3. Insert the known values into the equation, and solve. To express this as a percentage, multiply by 100 and add the percent sign, “%.”

79. STOP NOTES

80. Review Conservation of Energy Assume these were the numbers from the lab. Double check your numbers are in a similar range.  m = 55 g  h 1 =.31 m  h 2 =.91 m  d =.95 m 1. Find the time the car was in midair.  t = √(2h 2 /g) = ? 2. Find the car’s velocity when it hit.