Showing papers in "The Physics Teacher in 2004"

Assessing-To-Learn: Formative Assessment in Physics Instruction

Abstract: Assessment designed to enhance teaching and learning is called “formative assessment.” During formative assessment, teachers and students seek information about the state of student learning and then use the acquired information to adapt teaching and learning to meet student needs. “Classroom formative assessment” (CFA) requires that teachers explicitly engage in formative assessment during classroom learning activities. At a basic level, CFA occurs naturally and is a common part of most instructional settings. Nevertheless, the systematic practice of CFA is rare in secondary and post-secondary science education. Here we provide suggestions for those interested in formative assessment for use in teaching introductory physics. A simple model of classroom formative assessment is presented. Included are examples of formative assessment activities and suggestions for implementation.

Student Explorations of Quantum Effects in LEDs and Luminescent Devices

Abstract: We developed activity-based instructional units to introduce basic quantum principles to students with limited physics and mathematics backgrounds. To emphasize the practical applications of contemporary physics, we introduced concepts using the contexts of light-emitting devices such as light-emitting diodes (LEDs), fluorescent lamps, and glow-in-the-dark toys. As our standard of living becomes more dependent on the latest developments in science and technology, our students' literacy must be at a level that enables them to make educated decisions on science- and technology-related issues and their everyday applications. Students need to have at least a basic understanding of 20th-century physics and its applications in order to make informed decisions about them. Unfortunately, many physics teachers either exclude or spend very little time on modern topics such as quantum mechanics in high school physics courses.1,2 The high degree of mathematical formalism and abstract nature of quantum mechanics is frequently given as a reason for not introducing quantum physics in high school physics courses.3,4

Color Mixer for Every Student

Abstract: This paper describes the construction and use of a color light mixer that uses different color LEDs. The idea was partly inspired by two papers.1,2 The first one describes how a standard LED can be converted into a point-light source, and the second one explains how a Ping-Pong ball can be used to mix polarized color light from two lasers.

Exponential Versus Linear Amplitude Decay in Damped Oscillators

Abstract: The problem of oscillatory motion is, without any doubt, one of the main topics in physics from elementary up to advanced courses. An understanding of this motion is also relevant in many areas outside physics, including chemistry, biology, engineering, medical research, and economics to name a few. In physics, students encounter oscillatory behavior in classical mechanics, electricity, optics, and later in quantum mechanics.

Teaching Special Relativity Using Physlets

Abstract: In a recent paper in this journal1 we presented work on the creation and use of Physlet-based2 exercises to teach physical and wave optics. Since then we have developed ready-to-run exercises for introductory physics3,4 and have developed Physlet-based exercises for more advanced topics such as quantum mechanics. In this paper we describe the materials we have created to aid in the teaching and learning of introductory special relativity. There are many reasons to focus on special relativity. Special relativity is the first topic presented in the modern physics section of introductory physics courses and in the sophomore-level modern physics course. It is full of (apparent) paradoxes, and like quantum mechanics, is one of the intriguing theories that continues to captivate students' interest in physics. In addition, because special relativity focuses on abstract concepts, the visualization that Physlet-based material provides is especially valuable.

Tips for Using a Peer Response System in a Large Introductory Physics Class

Abstract: Teaching a large introductory physics course can be a challenge for a young physics instructor, and making a large physics lecture interactive may seem almost impossible. The most difficult part about the large class is that due to its size there is very little real-time interaction between the students and the lecturer. The instructor often does not know how well the students understand the lecture or how actively they are involved in it. The lack of real-time communication might make it very difficult and misleading for both the students and the instructor. Fortunately, recently we witnessed the proliferation of technological tools that can help the instructor get instantaneous feedback during the lecture. One of these tools is the peer response system (PRS).1

Just What Did Archimedes Say About Buoyancy

Abstract: “A body immersed in a fluid is buoyed up with a force equal to the weight of the displaced fluid.” So goes a venerable textbook1 statement of the hydrostatic principle that bears Archimedes' name. Archimedes' principle is often proved for the special case of a right-circular cylinder or rectangular solid by considering the difference in hydrostatic forces between the (flat, horizontal) upper and lower surfaces, and then generalized by the even more venerable “it can be shown…” that the principle is in fact true for bodies of arbitrary shape.

The Coefficient of Restitution of Baseballs as a Function of Relative Humidity

Abstract: The only published scientific data on the effect of humidity on baseballs known to the authors is contained in Robert Adair's book The Physics of Baseball: “long flies hit with balls stored under conditions of extreme humidity could be expected to fall as much as 30 feet short of the distance expected for normal balls.”1 In this paper we report on our measurements of the coefficient of restitution of baseballs as a function of the humidity at which they have been stored.

Rollover of Sport Utility Vehicles

Abstract: Recently, the PBS program “Frontline”1 examined the history of the development of the sport utility vehicle (SUV) and the efforts to force car makers to design SUVs that are less prone to rollover. The dangers of SUV rollovers were spotlighted in the fall of 2000, when the Ford-Firestone scandal prompted Congress to launch a series of hearings focusing on deaths and injuries related to faulty Firestone tires mounted on Ford Explorers. However, during the same 10-year period in which Ford-Firestone rollover crashes caused some 300 deaths, more than 12,000 people — 40 times as many — died in SUV rollovers unrelated to tire failure.1

Illustrating Electric Circuit Concepts with the Glitter Circuit

Abstract: Many beginning physics students have a harder time understanding basic concepts of electric circuits than understanding basic mechanics concepts. This is likely due to the fact that we cannot see electric charge carriers (electrons) move through an electric wire. It is thus the responsibility of the physics instructor to introduce his/her students to a variety of electric circuit models that will enable those students encountering circuits for the first time to come up with their own coherent mental picture of current flow in an electric circuit. Electric circuit analogs might prove helpful in this endeavor.

How Many Students Does It Take Before We See the Light

Abstract: Prior research suggests that students who cannot light a bulb given a single wire, a bulb, and a battery are not able to reason correctly regarding complete circuits. Our research shows that students believe that the wires from the filament are connected to the base of the bulb at the bottom. The percentage of students with this belief seems to be dependent on the level of the introductory physics course taken (conceptual, algebra, calculus). We have proposed three activities that appear to aid students in developing the correct model of how a light bulb is wired and a definition of complete circuit that classifies a short circuit as a complete circuit but one that is not advantageous.

The Metal Detector and Faraday's Law

Abstract: Electromagnetism has proven a notoriously difficult subject for beginning physics and engineering students. When simultaneously exercising their newly acquired calculus skills on abstract electromagnetism concepts, these students often lose the physics in the mathematical formalism. One way we have addressed this problem is by including engineering-style design and fabrication activities in the laboratory portion of the course. In addition to providing concrete examples of the electromagnetic concepts under study, the integration of mathematics and physics concepts in the design activities can significantly raise the level of student interest, increase the ownership of their learning, and ultimately improve learning and retention.

Energy and Momentum in the Gauss Accelerator

Abstract: James Rabchuk's recent paper1 describes a method for measuring the kinetic energy changes in the Gauss accelerator, as well as a calculation of the change in potential energy. In this paper, a simple method for measuring both the change in potential energy and the change in kinetic energy will be presented. The measurements can be made with rulers, strings, and weights. In the process, your students will learn about the relationship between work and potential energy as well as the law of conservation of energy. Issues associated with the law of conservation of momentum in the accelerator will also be addressed.

Getting Students to Provide Direction When Drawing Free-Body Diagrams

Abstract: Free-Body Diagrams (FBDs) are an essential part of teaching mechanics to students in an introductory physics course.1–3 While determining the forces acting on the body is of primary importance,4–6 this paper will not address that issue. Those who are interested in gaining more insight in how to determine the forces that are acting on a body are referred to the work of James E. Court.7,8 In this paper, an extra step in the standard technique is suggested: The student should include the forces' angles in the FBD. Importantly, these angles should be determined relative to appropriate coordinate axes imposed on the system. This step is not emphasized in the textbooks, a general fault for which they have previously been criticized.9,10 It is recommended that students be introduced to this technique after having achieved a reasonable level of mastery in the determination of forces in an FBD.

Energy Flow Diagrams for Teaching Physics Concepts

Abstract: Energy is arguably the central unifying concept in physics. The validity of the principles of energy extends almost without change from “classical” physics through all of modern physics. Even processes that are too complex or too far outside the Newtonian regime to be easily described in terms of forces can be described in an accurate and conceptually transparent manner in terms of energy. Thus, energy is a useful central organizing principle in teaching physics conceptually. Every physical process is an energy transformation of some forms of energy into other forms. “Energy flow diagrams” present these transformations visually and approximately quantitatively.1 Even for complex processes where analysis in terms of force and motion would be out of the question, energy flow diagrams show the physical fundamentals in a meaningful manner. This paper discusses energy flow diagrams for a few simple processes, and proceeds to complex socially significant processes.

Ready, SET, Go! A Research-Based Approach to Problem Solving

Abstract: I f there is one thing that physics educators are likely to agree on, it is the notion that learning problem-solving skills is one of the primary goals of physics education. In this article, I propose a set of problem-solving approaches—and separately, a set of related teaching strategies—based on the research project that I have recently completed.1 Before I go any further, I would like to stress the importance of distinguishing between problems and exercises. What definition of “problem” is useful when it comes to teaching problem-solving skills? Such a definition is a collective value judgment of many respected physics educators who have written on this subject. For instance, the article entitled “Exercises Are Not Problems” appeared in this journal more than 30 years ago.2 A problem, according to the author of that paper, is something that “puzzles and worries. The solution cannot follow any logical procedure, for if it does, the problem is not a problem but an exercise in following that procedure. Hence the obstacle to be overcome in problem solving must be a logical gap” (p. 236). Lawson & Wollman3 suggest that a problem-solving process must produce “contradictions ... [that] produce the state of disequilibrium ... patterns of reasoning are found wanting and must somehow be changed” (p. 470). The authors then suggest that problems must be such that “the student can partially but not completely understand them in terms of old ideas...; and sufficient time must be allowed ... to grapple with the new situation, possibly with appropriate ‘hints’” (p. 471). Fuller4 writes: “To develop reasoning, people need to be puzzled by their

The Freezing of Streams and Ponds: A Simple—But Uncomfortable—Experiment

Abstract: Within the span of a year, I twice faced the same question in slightly different forms. The first time it came from Tom Schlatter, who fields questions from readers of Weatherwise. He wrote to me that a reader had “asked why running water freezes more slowly than still water. The stock answer is friction, but I would like to do better than that.” I responded with quantitative arguments that (fluid) friction is irrelevant, and there the matter stood.

A Project-Based Approach: Students Describe the Physics in Movies

Abstract: Ted Sizer, founder of the Coalition of Essential Schools, calls for teachers designing a curriculum to begin with the end in mind; that is, determine your goals and only then design appropriate assignments and assessments that guide students toward these goals. Sizer argues that students should be tested via public “exhibitions” that drive the curriculum and set clear standards for students about what is expected of them.2 This paper describes an exhibition in which students analyze the physics of movies.

Determining the Heat Capacity Ratio of Air from “Almost Adiabatic” Compressions

Abstract: In this paper we demonstrate that the observed discrepancy between the measured and expected values of the heat capacity ratio γ = CP/CV for air obtained using the PASCO Adiabatic Gas Law Apparatus1 is due primarily to the finite compression time in the experiment. We devised an empirical method for obtaining a more accurate value of γ using this apparatus, which should be adaptable to other methods of measuring γ that use approximately adiabatic processes.

Simple Experiments to Study the Earth's Magnetic Field

Abstract: A set of simple experiments is outlined for determining the magnetic field of the Earth. These experiments can be performed by students from high school to college and will help them gain a greater appreciation of the three-dimensional nature for the Earth's magnetic field. Reasonably accurate measurements of the field strength, its components, and dip angle are possible through use of a transparent solenoid, a compass, and a Magnaprobe.

Know Your Students

Abstract: Welcome to your new role as physics teacher. I hope you will find the suggestions in this column useful as you try to put into practice all the strategies you have learned about teaching. Experienced teachers provide a wealth of ideas to help you develop skills to help your students learn physics. We all want to see you succeed not only at developing your skills as a teacher but also at building a love for the profession that will keep you with us for years to come.The following suggestions come from Randy Knight, a professor of physics at California Polytechnic State University in San Luis Obispo, CA. He is the author of Five Easy Lessons: Strategies for Successful Physics Teaching and the new textbook Physics for Scientists and Engineers: A Strategic Approach, both published by Addison-Wesley.

Magnetohydrodynamic Propulsion for the Classroom

Abstract: The cinema industry can sometimes prove to be an ally when searching for material with which to motivate students to learn physics. Consider, for example, the electromagnetic force on a current in the presence of a magnetic field. This phenomenon is at the heart of magnetohydrodynamic (MHD) propulsion systems. A submarine employing this type of propulsion was immortalized in the movie Hunt for Red October.1 While mentioning this to students certainly gets their attention, it often elicits comments that it is only fiction and not physically possible. Imagine their surprise when a working system is demonstrated! It is neither difficult nor expensive to construct a working system that can be demonstrated in the front of a classroom.2 In addition, all aspects of the engineering hurdles that must be surmounted and myths concerning this “silent propulsion” system are borne out in a simple apparatus. This paper details how to construct an inexpensive MHD propulsion boat that can be demonstrated for students in t...

Detecting Our Own Solar System from Afar

Abstract: As the list1 of extra-solar planets orbiting Sun-like stars continues to grow, more members of multiple-planet systems2 are being discovered An intriguing way to bring the data and detection methods for extra-solar planets into the classroom is to ask the question, “What would our solar system look like if viewed from afar by an observer using the same detection methods that we do?”

Polymer Physics in an Introductory General Physics Course

Abstract: Do all solids expand upon heating? To most people's surprise, there is a class of rather common solids, namely rubbery elastic polymers, capable of contracting upon heating1,2 while staying in the same solid phase. This seems contradictory to common sense and the physical theories of thermal behavior of ordinary solids. The physical behavior of elastic polymers continues to amaze physics and chemistry students as well as many scientists, despite the fact that it was experimentally detected in natural rubbers two centuries ago. For the following 125 years this phenomenon remained unexplained. An explanation was finally found only in the 1930s when the new science of “polymer physics” emerged. The goal of this paper is to demonstrate that some elements of polymer physics can be useful in teaching introductory general physics, especially in discussing the thermal properties of solids and for introducing the concept of entropy. Initially, several simple demo/lab experiments manifesting the extraordinary therm...

Model Rocketry in the 21st-Century Physics Classroom

Abstract: Model rocketry has changed since my introduction to it as an eighth-grade student. Two of these changes are important for the use of rocketry in the physics classroom. First, simulation software,1 which is relatively inexpensive and very powerful, allows students to create and fly virtual models of their rocket designs. Second, lightweight and sophisticated electronics2 are available for logging flight data and for controlling flight operations such as deploying parachutes. In this technology-rich context, designing, building, and flying model rockets can capture the interest of today's physics students.

An Inexpensive Interferometric Setup for Measuring Microscopic Displacements

Abstract: In an interesting article published in an issue of The Physics Teacher, Reichert1 gives some didactic examples about static friction force between a plastic block and a wooden plane on which it rests. To explain the experiments, he uses a simple model based on a microscopic “elastic band” that connects the atoms of both surfaces. Reichert remarks that “the block moves, albeit a microscopic distance,” and that it would be helpful if the student could see these displacements. In another paragraph he states that “measuring it (displacement) requires delicate and expensive optical instruments.” Effectively, a measurement of such small displacements generally requires interferometric devices. At our university, we teach basic physics and we are aware of the difficulties that beginners have grasping the concepts involved in static friction force. At the same time, as our research field is related to optics metrology, we could not ignore Reichert's statement. Could we design an experimental device to measure the microscopic displacement referred to by Reichert, keeping it inexpensive and easy to implement? Incidentally, in the same issue of The Physics Teacher, Sawicki2 gives an excellent example of how, with a few common elements, a simple experiment of interferometric measurement can be put within students' reach. In this paper, we suggest the use of a simple interferometric device, built with very common and inexpensive elements, and describe an experiment on static friction force in which the instrument is applied to measure microscopic displacements.

A Multipurpose LED Light Source for Optics Experiments

Abstract: The traditional light source for studying lenses and mirrors is either a bare white light bulb,1 or one encased inside a lamphouse.2, 3 A simple pattern like an arrow, mounted on an optical bench or printed on the window of a lamphouse, serves as the object. Ironically, the image captured on a translucent screen is often the shadow of the pattern with no light falling on it. Although LEDs have been used in commercial display boards for decades, the advantage of using LEDs as a multipurpose light source in the physics laboratory has been overlooked by many physics teachers. In this paper, we remind readers of a few examples of how LEDs can be used to replace the incandescent lamp for geometrical optics, physical optics, and fiber optics experiments.