1. Chapter 5: Work, Energy, & Power Section 5.1: Work pages 83 to 86 Section 5.2: Energy Conservation pages 87 to 90 Sections 5.3: Energy Transformations pages 91 to 94

2. Priority Academic Student Skill Content Standard 3: Interactions of Energy and Matter – Energy, such as potential, kinetic, and field, interacts with matter and is transferred during these interactions. CS 3: 1 All energy can be considered to be either kinetic energy, which is energy of motion, potential energy, which depends on the relative position; or energy contained by a field, such as electromagnetic waves.

3. Section 5.1: Work pages 83 to 86 Four subsections 1.What is work? Page 83 2.Work done by a machine Page 84 3.Efficiency Page 85 4.Power Page 86

4. 5.1: Work: What is work? (2 of 3 parts) 1.The word work means many different things 2.What work means in physics The word work is used in many different ways In physics, work is force times distance. W = Fd * Work in joules (J) * Force in Newtons (N) Distance in meters (m)

5. 5.1: Work: What is work? (1 of 3 parts) 3. Machines do work in the physics sense When we apply force to machines we are doing work. To be exact, work is force times distance moved in the direction of the force.

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7. Quiz for page 83: What is work? 1.Define work. 2.If a machine has a constant speed, is work being done? Why or why not? 3.In order to state that work is being done, work must be done the direction of the _________. 4.What are the units for each of the components of the work equation?

8. 5.1: Work: Work done by a machine page 84 (2 of 3) 1.Work is done by forces on objects 2.Units of work * In physics, work is done by forces. Work is done on the objects. Work is measured in joule (J) which is equal to one newton of force times one meter of distance.

9. 5.1: Work: Work done by a machine page 84 (1 of 3) 3.Input work and output work a.Refer to page 84 – Figure 5.3 b.Refer to page 84 – Figure 5.4 c.The work output of a simple machine can never exceed the work input. d.When you design a machine that multiplies force, you pay by having to apply the force over a greater distance.

11. 5.1: Work: Efficiency page 85 (2 of 4) 1.What is an efficient machine? * a.All (or most) of the work input becomes work output b.Five joules of work input with five joules of work output. 2.How friction affects real machines In real machines, the work output is always less than the work input due to friction and other forces.

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13. 5.1: Work: Efficiency page 85 (2 of 4) 3.The definition of efficiency * a. The efficiency of a machine is the ratio of work output to work input i.e. work output divided by work input times 100.* output divided by work input times 100.* b. Efficiency is usually expressed in percent. Refer to page 85.* percent. Refer to page 85.* 4.The ideal machine The ideal machine would be 100 percent efficient. Efficiency cannot exceed 100%*

14. A most efficient machine page 85 BONUS information for use on the content exam chapter 5

15. 5.1: Work: Power page 86 (2 of 3) 1.How fast the work is done It makes a difference how fast you do work. 2.What is power? * a. The rate at which work is done is called power. b. Power is work done over time * c. Refer to the example on page 86 *

16. 5.1: Work: Power page 86 (1 of 3) 3.The units of power * a. Power is measured in Watts (W) b. Work is measured in joules (J) c. Time is measured in seconds (s) d. The Watts can also be known as horsepower: one horsepower equals horsepower: one horsepower equals 746 Watts. 746 Watts.

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18. 5.2: Energy Conservation: What is energy? page 87 (1 of 2) 1.The definition of energy a. Energy is the ability to do work. a. Energy is the ability to do work. b. Any object that has energy has the ability to create force. b. Any object that has energy has the ability to create force. c. Energy is one of the fundamental building c. Energy is one of the fundamental building blocks of our universe. blocks of our universe.

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20. 5.2: Energy Conservation: What is energy? page 87 (1 of 2) 2.Units of energy a. Energy is measured in joules (J) b. Energy is really stored work. c. Any object with energy has the ability to use its energy to do work, which to use its energy to do work, which means creating a force that acts over a means creating a force that acts over a distance. distance.

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22. 5.2: Energy Conservation: Potential energy page 88 (2 of 4) 1.What is potential energy? a. Comes from the position of an object relative to the Earth. b. Refer to Figure 5.6 page 88 2.Where does potential energy come from? Energy is stored work, so the amount of energy must be the same amount of work done to lift an object up.

23. 5.2: Energy Conservation: Potential energy page 88 (1 of 4) 3.How to calculate potential energy a. Force required to lift an object is the weight of the object. weight of the object. b. Work is done to lift the object so the equation for work is needed. equation for work is needed. c. Potential energy is a type of energy so the unit is in joules (J) so the unit is in joules (J)

24. E p = m g h Potential Energy Equation E p is potential energy in (J) m is mass in kilograms (kg) g is gravity in 9.8 m/s 2 h is height that the object was lifted in meters (m)

25. 5.2: Energy Conservation: Potential energy page 88 (1 of 4) 4.Why is it called potential energy? a. Objects that have potential energy do not use their energy until they move. b. Potential means that something is capable of becoming active. capable of becoming active. c. Any object that can move to a lower place has the potential to do work on place has the potential to do work on the way down, such as a ball down a the way down, such as a ball down a hill. hill.

26. 5.2: Energy Conservation: Kinetic energy page 89 (2 of 5) 1.Kinetic energy is energy of motion a. Objects also store energy in motion. b. Refer to Figure 5.7 page 89 2.Kinetic energy increases with speed The higher the speed of an object, the more energy it has because you have to do work to increase the speed.

27. 5.2: Energy Conservation: Kinetic energy page 89 (1 of 5) 3.Kinetic energy increases with mass Increasing the mass increases the amount of work you have to do to get an object moving, so it also increases the energy. KINECTICE ENERGY DEPENDS ON TWO THINGS: MASS AND SPEED.

28. 5.2: Energy Conservation: Kinetic energy page 89 (1 of 5) 4.The formula for kinetic energy a. Requires work just like potential energy energy b. The work has to get the object with a mass (m) from a resting position to mass (m) from a resting position to speed (v). speed (v). c. The unit for kinetic energy is the same as the unit for potential energy in joules (J) joules (J)

29. E k = ½ mv 2 Kinetic Energy Equation E k is the K.E. in joules (j) m is the mass of object in kilograms (kg) V 2 is the speed in meters per second squared (m/s) 2

30. 5.2: Energy Conservation: Kinetic energy page 89 (1 of 5) 5.Kinetic energy increases as the square of speed a. This means if you do twice as fast, your energy increases by four times your energy increases by four times b. More energy means more force is needed to stop needed to stop c. At a speed of 90 mph you have nine times as much energy as you did at 30 times as much energy as you did at 30 mph. mph.

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32. 5.2: Energy Conservation: Conservation of energy* page 90 (1 of 4) 1.The law of conservation of energy* a. Nature never creates or destroys energy; energy only gets converted energy; energy only gets converted from one form to another. from one form to another. b. The rule we found for the input and output work of a machine was an output work of a machine was an example of the law of conservation of example of the law of conservation of energy. energy.

33. 5.2: Energy Conservation: Conservation of energy page 90 (1 of 4) 2.An example of energy transformation Read the three paragraphs on page 90 3.The total energy never exceeds the starting energy The energy is divided between potential and kinetic, but the total is unchanged.

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35. 5.2: Energy Conservation: Conservation of energy page 90 (1 of 4) 4.Friction can divert some energy a. The law of conservation of energy still holds true, even when there is holds true, even when there is friction. friction. b. The energy converted to heat or wear is no longer available to be potential is no longer available to be potential or kinetic energy, but it was not or kinetic energy, but it was not destroyed. destroyed.

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37. 5.3: Energy Transformations: Following an energy transformation page 91 & 92 (1 of 7) 1.The different kinds of energy a. Kinetic and potential energy are often called mechanical energy because called mechanical energy because they involve moving objects. they involve moving objects. b. There are many other kinds of energy, including radiant energy, energy, including radiant energy, electrical energy, chemical energy, & electrical energy, chemical energy, & nuclear energy. nuclear energy.

38. 5.3: Energy Transformations: Following an energy transformation page 91 & 92 (2 of 7) 2.An example of energy transformation Refer to page 91 Figure 5.10 3.Chemical energy to potential energy a. The chemical potential energy stored in the food you ate is converted into simple the food you ate is converted into simple sugars. sugars. b. In climbing the hill, you convert some chemical energy to potential energy. chemical energy to potential energy.

39. 5.3: Energy Transformations: Following an energy transformation page 91 & 92 (1 of 7) 4.Where does “spent” energy go? a. Some of the energy you spent is now stored as potential energy because your position is higher than when you began. position is higher than when you began. b. Some of the energy was converted by your body into heat, chemical changes in muscles, and the evaporation of sweat from your skin.

40. 5.3: Energy Transformations: Following an energy transformation page 91 & 92 (2 of 7) 5.How does potential energy get used? The increased potential energy is used when converted to kinetic energy 6.Kinetic energy is used up in the brakes Brakes convert kinetic energy into heat and the wearing away of the brake pads.

41. 5.3: Energy Transformations: Following an energy transformation page 91 & 92 (1 of 7) 7.The flow of energy a. Refer to page 92 Figure 5.12 b. During all the energy transformation in Figure 5.12, no energy was lost in Figure 5.12, no energy was lost because energy can never be created because energy can never be created or destroyed. or destroyed.

42. 5.3: Energy Transformations: Other forms of energy page 93 & 94 (2 of 8) 1.Energy: nature’s money Energy is used to buy speed, height, temperature, mass, and other things which diminishes as you use it. 2.Mechanical energy a. Can be either kinetic or potential energy energy b. Is form involved in the operation of simple machines. simple machines.

43. 5.3: Energy Transformations: Other forms of energy page 93 & 94 (2 of 8) 3.Radiant (meaning light) energy a. AKA electromagnetic energy b. Electromagnetic waves includes light we see, ultraviolet light (UV), X rays, infrared see, ultraviolet light (UV), X rays, infrared radiation ( AKA heat), radio waves, radiation ( AKA heat), radio waves, microwaves, and radar. microwaves, and radar. 4.Energy from the sun Radiant heat from the sun is what keeps the Earth warm. 1,400 Watts per square meter.

44. 5.3: Energy Transformations: Other forms of energy page 93 & 94 (2 of 8) 5.Electrical energy 6.Chemical energy 7.Nuclear energy 8.Thermal energy