Textbook Review

Ethan Jewett 10/09/06 Textbook Review

Part I: The book is Physics by Jerry D. Wilson and Anthony J. Buffa (1997). It is published by Prentice-Hall Publishing Company and is designed for 11th and 12th graders in a mainstream, algebra-based physics class. The book is designed to be an introductory text and does not cover calculus, however it stresses still the use of equations to describe physical phenomena over conceptual understanding.

Part II: The learning expectation is Energy Transfer from the Michigan Course Expectations. The expectation reads as follows:

P4.1 Energy Transfer: Moving objects and waves transfer energy from one location to another. They also transfer energy to objects during interactions (e.g., sunlight transfers energy to the ground when it warms the ground; sunlight also transfers energy from the Sun to the Earth.

Essential: - Account for energy transfer and be able to construct energy transfer diagrams. - Be able to explain energy transfer by waves and moving massive objects.

Core: - Explain how "work" as it is defined in physics is different from "work" as it is defined in everyday life. - Calculate the amount of work done in moving an object from one point to another. - From the formula for work, derive a formula for the change in potential energy when an object is elevated by a distance h.

What this expectation means:

This expectation means that students should be able to:

 Explain that energy is lost and gained through interactions of systems and draw a diagram showing the kinds of energy that are input to and output from a system in a given interaction.

 Explain that collisions result in some or all energy (or no energy in the case of annihilations) being transferred between objects. Students should be able to make qualitative predictions about the objects and their energies following a collision. They should also be able to explain how transverse and longitudinal waves in a medium transfer energy through collisions and that electromagnetic waves transfer energy through varying electric and magnetic fields that cause movement of charged particles in materials. At this point they do not need to understand gravitational waves.

 Explain that the term work refers to a net output or input of energy through mechanical action. They should be able to explain that work has a specific definition in physics and be able to state that work is the energy required to displace an object by a certain amount. They should understand that work can be done on a system and that this work is taken to be a negative quantity in terms of the energy of the system. They should also be able to use the formula W=Fd to calculate work done on a system. Students should be able to use this formula and their knowledge that gravity applies a constant force to an object with a given mass to calculate the work required to move an object up or down by a distance d.

 Calculate the energies of two objects before and after a collision.

Part III: Criterion III.A: Providing a variety of Phenomena: A Note on phenomena: For the purpose of evaluating the variety of phenomena in the text, I counted both phenomena and representations in making my decision. This is because the review criteria mention variety in the case of phenomena and not in the case of representation so I assumed that they were using the term phenomena in a general way (otherwise they would have asked about variety for representations as well). However, when evaluating the quality of individual sightings, I reviewed phenomena and representations separately.

Energy Transfer: Sighting Ind1 Ind2 p. 181 Description of two steel or billiard balls bouncing off each other. The passage is Yes Yes short and relies on the reader having experienced the phenomenon rather than describing it. However, the example satisfies both the criteria because the idea of objects colliding elastically illustrates energy transfer and the text explicitly mentions energy transfer between the two balls. p. 181 Picture and caption of bumper cars: elastic collision. This satisfies the two criteria Yes Yes because it is another example of two objects transferring energy through a collision and the text explicitly mentions the transfer of energy between the two cars. p. 181 Picture and caption of real cars: inelastic collision. This satisfies the two criteria Yes Yes because it is another example of two objects transferring energy through a collision and the text explicitly mentions the transfer of energy between the two cars. p. 182 Description of a steel ball colliding with a hollow aluminum ball: inelastic collision. Yes Yes This satisfies the two criteria because it is another example of two objects transferring energy through a collision and the text explicitly mentions the transfer of energy between the two balls. p. 187 Picture and description of Newton's balls toy. This sighting is a good example of Yes Yes how energy is transferred between colliding objects. The text also explicitly relates energy the example to energy transfer by doing a calculation to show why two balls fly off when two are dropped. Therefore, it satisfies the two indicators. p. 372 Description of energy transfer by standing next to a fire. This satisfies the two Yes Yes criteria because it can be used to exemplify energy transfer by radiation and because the text explicitly mentions the energy being transferred. p. 373 Picture: Infrared image of man with his arm above his head. This image could be Yes No used to discuss energy transfer by EM radiation, but the text does not explicitly mention energy transfer. Therefore it satisfies the first, but not the second criterion. p. 374 Description of the Greenhouse Effect. This sighting can be used as an example of Yes Yes energy being transferred from EM waves to matter. The sighting discusses how energy is transferred from EM waves to molecules in the atmosphere and on the surface of the Earth. It therefore satisfies both indicators. p. 374 Description of heat transfer by a microwave. This sighting can be used as an Yes Yes example of how EM waves can transfer energy to matter. It says that energy is transferred from microwaves to water molecules in food. It therefore satisfies both indicators.

Evaluation: Although each of the phenomena related to energy transfer that were presented satisfied both the criteria, the examples consisted primarily of pictures or descriptions of two objects bumping into each other, or of energy being transferred by EM waves. Because energy transfer can also occur through propagation of non-EM waves, heat transfer, electrical induction, etc., I gave the text a grade of satisfactory for failing to cover more than two forms of energy transfer.

Sighting Ind1 Ind2 p. 133 Picture and discussion of a cherry-picker crane in a sulfur mine. This sighting is Yes Yes used to demonstrate the difference between the physics definition of work and the “real world” definitions of work. It exemplifies the difference between the “real world” and physics definition by noting that the crane does no work (by the physics definition) in simply holding someone aloft. The phenomenon of the crane is used to explain the difference between the two definitions so it satisfies the second indicator as well. p. 134 Statement that water running through a dam does work on a turbine. Although Yes Yes this example does not explain how water does work on a turbine, it can be used to illustrate work and it directly states that the water does work. Therefore, it satisfies the two indicators. p. 134 List of some different examples of situations that involve the “real world” Yes Yes definition of work. These examples include homework, working out, manual work, etc. This sighting can be used to describe the difference between the two definitions and also explicitly connects the definitions of work to the situation. Therefore, it satisfies the two indicators. p. 142 Picture and caption of a crater: The text shows a picture of a crater in Arizona Yes Yes and says that it took work to make the crater. This example can be used to illustrate work by looking at the force on the meteorite as it slows down on impact over a certain distance, and it explicitly states that work was done in forming the crater. Therefore it satisfies the two indicators. p. 145 Picture and caption of someone drawing a bow. This sighting illustrates that it Yes Yes takes work to draw a bow. Although it relies on someone having experience with drawing a bow, it nonetheless can be used to illustrate work done with a variable force and explicitly relates work to the phenomenon. Therefore, it satisfies the two indicators. p. 157 Picture and exercise involving hoisting an object with a crane. This sighting can Yes Yes be used to show that it takes work to lift an object against the force of gravity. It also explicitly asks students to calculate the work done so it satisfies the indicators.

Evaluation: The text listed several examples of objects doing work on other objects and each of the phenomena satisfied the two indicators. Therefore, I gave the text a grade of excellent on the topic of work.

Criterion III.B: Providing vivid experiences:

Energy Transfer:

Sighting Ind2 p. 181 Description of steel or billiard balls bouncing off each other. The description No assumes that someone has seen two balls bounce off of each other so it does not satisfy the indicator. p. 181 Picture and caption: Bumper cars: elastic collision. Although there is a picture, No both the image and caption assume that someone has seen bumper cars bounce off of each other. Therefore, it does not satisfy the indicator. p. 181 Picture and caption: Real cars: inelastic collision. Although there is a picture, No both the image and caption assume that someone has seen a collision. Therefore, it does not satisfy the indicator. p. 182 Description of a steel ball colliding with a hollow aluminum ball: inelastic collision. No The sighting assumes that people have experience with squashing aluminum so it does not satisfy the indicator. p. 182 Drawing: Energy transfer in case of two balls colliding. The sighting assumes No that people have experience with squashing aluminum so it does not satisfy the indicator. p. 183 Exercise: Energy transfer in case of two balls colliding. The sighting assumes No that people have experience with squashing aluminum so it does not satisfy the indicator. p. 184 Drawing: Energy transfer in case of two balls colliding: elastic. The sighting No assumes that people have experience with squashing aluminum so it does not satisfy the indicator. p. 186 Drawing: Energy transfer in case of two balls of different masses colliding: No elastic. The sighting assumes that people have experience with squashing aluminum so it does not satisfy the indicator. p. 186 Exercise: Bowling ball with pin: elastic. The sighting assumes that people have No experience with squashing aluminum so it does not satisfy the indicator. p. 187 Picture: Newton's balls conservation of energy. This example assumes that the No reader is familiar with two balls colliding in an elastic collision and that they can imagine the ball swinging on the string. Therefore, it does not satisfy the indicator. p. 197 Exercise: Ballistic pendulum: inelastic. This requires that people be able to No imagine a bullet being fired into a block of wood. p. 199 Exercise: Two balls colliding at 90 degrees. This problem assumes that people No are familiar with balls colliding. p. 372 Description: Energy transfer by standing next to a fire. This description requires No that people be familiar with heat transfer from fires. p. 373 Picture and caption: Infrared image of man with his arm above his head. No Although this picture provides a good sense of heat being transferred into EM radiation, it does not specifically focus on energy. p. 374 Description and drawing: Greenhouse effect. This picture provides a good (yet No simple) description of the greenhouse effect and energy absorption. However, it does not provide a very good visual representation of how heat is transferred from EM waves to molecules. It does mention that heat is transferred through resonance, but it is not specific. p. 374 Description and drawing: Heat transfer by microwave. Again, this is a good, but No simplistic representation of heat transfer. Unfortunately, the picture does not provide enough information for students to imagine how heat is transferred.

Evaluation: Although many of the sightings assume prior knowledge, it might be possible to assume that people have experience with these phenomena. Therefore, these sightings could be rated as satisfying Indicator 2 because they adequately relate the phenomenon to the concept. As a result, the text can either be scored as satisfactory (because it provides a long, but not comprehensive list of examples which is, therefore, insufficient ), or as poor (because it provides no (or only very bad) examples from which students can gain an idea of the phenomenon), depending on the assumption about student prior knowledge. I would assume that students have enough prior knowledge so I would give the text an overall rating of satisfactory on this point.

Sighting Ind2 p. 133 Picture and discussion of a cherry-picker crane in a sulfur mine. This example Yes has a good picture and a lengthy discussion that allow the student to understand the situation well. It satisfies Indicator 2. p. 134 Statement that water running through a dam does work on a turbine. This is only No a short statement and relies on students being familiar with turbines. It does not satisfy the indicator. p. 134 List of some different examples of situations that involve the “real world” definition Yes of work. Students should be familiar with these usages of the word so it provides a good context for understanding the common usage of the word work. It satisfies the indicator. p. 135 Drawing: Work expended to move a box. This drawing and caption with the Yes forces included provides enough information for students to imagine and understand the situation and concept. p. 135 Drawing: Work expended to pull a water skier. This drawing and caption with the Yes forces included provides enough information for students to imagine and understand the situation and concept. p. 135 Drawing: Work expended to push a lawn mower. This drawing and caption with Yes the forces included provides enough information for students to imagine and understand the situation and concept. p. 135 Drawing and caption: Work by gravity on book. This drawing and caption with the Yes forces included provides enough information for students to imagine and understand the situation and concept. pp. 136-137 Drawing and exercise: Work moving block up inclined plane. This drawing Yes and caption with the forces included provides enough information for students to imagine and understand the situation and concept. pp. 138-139 Drawing and explanation: Work done on spring. This drawing and Yes explanation provide enough information for students to imagine and understand the situation and concept. p. 140 Drawing: Work done on a spring. This drawing with the forces included provides Yes enough information for students to imagine and understand the situation and concept. p. 141 Exercise: Work done on a spring. The drawing and explanation within the Yes problem provide enough information for students to imagine and understand the situation and concept. p. 141 Drawing and description: Work done on a block on a frictionless surface. This Yes drawing and explanation with the forces included provides enough information for students to imagine and understand the situation and concept. p. 142 Picture and caption: Wrecking ball doing work. This picture and caption provide Yes enough information for students to imagine and understand the situation and concept. p. 142 Picture and caption: Work done by a meteorite in making a crater. This picture Yes and caption provide enough information for students to imagine and understand the situation and concept. pp. 142-143 Drawing and exercise: Work in stopping a shuffleboard puck. The drawing Yes and explanation within the problem provide enough information for students to imagine and understand the situation and concept. p. 145 Picture and caption: Doing work to bend a bow. This picture and caption provide Yes enough information for students to imagine and understand the situation and concept. p. 146 Drawing: Work done in lifting a can of soda. This drawing and caption with the Yes force included provide enough of the sense of the real phenomenon to allow students to imagine it. p. 157 Picture and exercise: Hoisting an object with a crane. This picture provides Yes enough of the sense of the real phenomenon to allow students to imagine it. p. 160 Picture and exercise: Work done by a weight lifter. This picture provides enough Yes of the sense of the real phenomenon to allow students to imagine it. p. 161 Drawing and exercise: Work done pulling a kid on a sled. This drawing provides Yes enough of the sense of the real phenomenon to allow students to imagine it. p. 166 Drawing and exercise: Work done by a horse pulling a sleigh. This drawing Yes provides enough of the sense of the real phenomenon to allow students to imagine it. Evaluation: The section on work tended to provide good explanations and photos/drawings of phenomena that were relevant to the topic. Many examples, such as the meteorite and shuffleboard depictions require prior knowledge, but students may reasonably be expected to possess the prior knowledge necessary for them to get a sense of these phenomena from the pictures. Overall, the text received a score of excellent on this criterion.

Criterion IV.B: Representing ideas effectively:

Energy Transfer:

Sightings Ind1 Ind2 Ind3 p. 182 Drawing: Energy transfer in case of two balls colliding: elastic and Yes Yes Yes inelastic. p. 183 Drawing and exercise: Energy transfer in the case of two balls colliding: Yes Yes Yes inelastic. p. 184 Drawing: Energy transfer in the case of two balls colliding: elastic. Yes Yes Yes p. 186 Drawing: Energy transfer in the case of two balls of different masses Yes Yes Yes colliding: elastic. p. 186 Drawing and exercise: Bowling ball with pin: elastic. Yes Yes Yes p. 197 Drawing and exercise: Ballistic pendulum: inelastic. Yes Yes Yes p. 199 Drawing and exercise: Two balls colliding at 90 degrees. Yes Yes Yes p. 374 Drawing: Greenhouse effect. Yes No Yes p. 374 Drawing: Heat transfer by a microwave. Yes No Yes

Evaluation: Most of the representations would be familiar to students. Further, they included arrows denoting forces that should be intuitive to students. Overall, they were accurate, comprehensible, and explicitly linked to the actual phenomenon. The only exceptions were the representations of the greenhouse effect and heat transfer by a microwave. In these examples, there was no discussion of how energy is actually transferred from EM radiation to matter. Further, the descriptions are convoluted and it is likely that students would be confused. Although most representations met all three indicators, there were only two types of energy transfer depicted in the representations. Therefore, the text received a rating of satisfactory.

Sighting Ind1 Ind2 Ind3 p. 135 Drawing: Work expended to move a box. Yes Yes Yes p. 135 Drawing: Work expended to pull a water skier. Yes Yes Yes p. 135 Drawing: Work expended to push a lawn mower. Yes Yes Yes p. 135 Drawing and caption: Work by gravity on book. Yes Yes Yes pp. 136-137 Drawing and exercise: Work moving block up inclined plane. Yes Yes Yes pp. 138-139 Drawing and explanation: Work done on spring. Yes Yes Yes p. 140 Drawing: Work done on a spring. Yes Yes Yes p. 141 Exercise: Work done on a spring. Yes Yes Yes p. 141 Drawing and description: Work done on a block on a frictionless surface. Yes No Yes pp. 142-143 Drawing and exercise: Work in stopping a shuffleboard puck. Yes Yes Yes p. 146 Drawing: Work done in lifting a can of soda. Yes Yes Yes p. 161 Drawing and exercise: Work done pulling a kid on a sled. Yes Yes Yes p. 166 Drawing and exercise: Work done by a horse pulling a sleigh. Yes Yes Yes

Evaluation: Most of these examples provide good pictures with helpful arrows showing forces. They are accurate, comprehensible, and explicitly linked to the concepts being taught. The one exception is the diagram of how doing work on a block on a frictionless surface increases its kinetic energy since it has very little explanation to accompany it and people are not used to doing work on blocks on frictionless surfaces. The shuffleboard problem is like the example with the block, but more detailed in its description of how energy is transferred through work into kinetic energy. Perhaps the best example here is the depiction of someone pulling a child on a sled. Students (if they are from northern climes) are familiar with the fact that it takes work (even in its everyday definition) to pull someone on a sled and this example is good for illustrating the definition of work as force times distance. Overall, the text received a grade of excellent on this criterion.

Part IV:

Overall, I rated the text very highly, however I feel that this is more a result of the indicators used than the quality of the text. First, I feel that the examples are dry and are likely to merely suffice rather than engage students. Second, there is not a wide variety of examples to demonstrate the concepts in many settings. This is regrettable since students have difficulty transferring these concepts and are likely to progress through life with a very narrow view of them if this text is all they have to go on. Therefore, it would be advisable to include many more examples, especially those drawn from real life, that exemplify the concepts in more diverse situations and appeal to a wider range of students. Many of the elements in the text are good examples and should be retained. They include collisions between balls and cars, Newton’s balls, heat radiated by a fire, the greenhouse effect, microwaves, work done on a spring, work done lifting a can of soda, work done by a crane in lifting an object, work done drawing a bow, work done by gravity on a falling object, and work done pulling a child on a sled. However, some of these examples will need to be modified so that they will be more engaging and comprehensible. Further, they will have to be modified from passive displays to interactive exercises so that students will be forced to question their understanding of the concepts.

Examples I would modify

I would keep a fair number of the descriptions, drawings, and pictures of balls colliding. These examples are simple enough so that the phenomenon of interest is not obscured by other, extraneous elements. However I would also include a link to a web page of java applets showing collisions so that students could gain a better understanding of how energy and momentum are transferred. I would also include questions that guide students through the process of thinking about what energy is and about how they think energy transferred. Because people tend to feel confident in their level of understanding when they feel they can work intuitively with a concept, it is necessary to push them beyond this level and force them to question what they take for granted. Therefore, since people are familiar with objects colliding, it is necessary to force them to question the nature of energy and what is actually happening in a collision in order to force them beyond this level of intuitive acceptance.

I would modify the bumper car example because the collision is not very elastic and therefore might give students a misguided idea of elastic collisions. I might modify this example by including it in a later section that discusses energy transfer and transformation in collisions, and include questions about the ways in which energy is transferred and transformed both macroscopically and at the molecular level.

The discussion and picture of the Newton’s balls toy is a good way to help students understand the nature of collisions because it presents an interesting phenomenon and gets students engaged. The book presents students with a set of good questions that will help them to understand what would happen if a ball of mass 2m were dropped, but it does not do the same for the case of two balls of mass m being dropped. I would modify this example by including questions about what happens at each ball in the line and have them analyze individual collisions.

The greenhouse effect and microwaves are both good examples of the transfer of energy from EM waves to matter and should be included in a discussion of energy transfer. However, neither of the examples in the text give students a drawing or heuristic for how this transfer occurs and therefore, leave them at an unnecessarily superficial level of understanding. I would modify these examples by including a representation of an EM wave causing a molecule to vibrate and a picture of a laser hitting and heating a surface. Further, I would include a link to a java applet on the web showing a heuristic of how the EM field in an EM wave causes molecules to move. I would also re-word the description of the greenhouse effect to make it less confusing, but I would still discuss the concept in the text because it is important and because it will help students to connect heat transfer by EM waves to real life.

The example of the child being pulled on a sled should be moved from the end of chapter exercises to the main part of the text. Further a list of questions should be added to help students think about where the energy of the puller is going.

It may be difficult for students to relate the examples of the wrecking ball and the meteorite to the definition of work that has been discussed in the chapter. This is because it is not clear that any particular object is being pushed a particular distance by the wrecking ball or meteorite. This confusion results from the fact that the captions put emphasis on the ball and meteorite doing work rather than having work done to them. It is much easier to relate these examples to the definition W = Fd, if one notes that the ball and meteorite are being decelerated over a given distance and are therefore subject to a force.

The example of work done to accelerate block on a frictionless surface will need to be modified to include a set of questions that explicitly discuss how work is related to the kinetic energy. This problem currently discusses the problem only by comparing work (as an energy) to the final kinetic energy. It does not directly relate the definition of work as W = Fd to energy and, therefore, fails to accomplish the goal of the section. One way this example could be improved is by reminding students of how an acceleration over a certain distance alters the velocity of an object. The example of the work done by gravity on a falling book should be modified to include a list of questions about forces on the book. I always struggled with the idea that gravity is exerting a force on an object in freefall and I think it is necessary to ask students questions that will guide them to this realization/interpretation on their own so that they will understand how gravity is doing work. This example should also appear after the modified example of a block on a frictionless surface.

Examples I would add

Most of the examples of energy transfer have to do with collisions of one type or another. Although collisions are often the fundamental mechanism by which energy is transferred, it is important to discuss a variety of situations in which collisions or transfer by EM waves takes place. Therefore, I would include examples of heat transfer, energy transfer through electrical induction, and energy transfer through sound waves, among others.

1) One example of energy transfer through sound would be a picture of a speaker being used to cause an object to resonate. This could be packaged with a quicktime movie showing feedback from a speaker, or showing an object vibrating and eventually falling over due to resonance at a particular frequency. One example that is particularly vivid is a movie of an opera singer shattering a class with a high note.

2) An example of energy transfer through electrical induction might be a diagram of a transformer or a link to a quicktime movie showing a bar magnet creating a current in a loop of wire.

3) An example of heat transfer might be a picture of an iron bar being heated to red-hot from one side.

How I would help students work through the text

In order to help students use the text effectively, I would provide them with sets of questions for each example that force them to think about aspects they might otherwise take for granted. For each example, I would include several different sets of questions that differ in the level of specificity with which they guide students through the process of thinking about a phenomenon. I would encourage students to avoid consulting these guides unless they were unable to solve the problem on their own. This is because a set of guiding questions necessarily reflects a particular approach to thinking about a problem and I would prefer that students develop their own ways of thinking. After they have thought about a phenomenon and arrived at a description/explanation that is satisfactory to them, I would encourage them to write up their thoughts in a public forum and to consult what others have written. This will allow them to see other ways of thinking and provide a check on their interpretation of the text. I would also provide them with links to java applets to help them gain hands on experience with the concepts. The text is primarily useful as a reference for relating concepts to equations once an intuitive understanding has been achieved. Therefore, I would help students build an intuitive understanding of concepts through hands-on activities and then refer them to examples in the book when it came time to relate phenomena to equations.