Showing papers in "American Journal of Physics in 1999"
3,510 citations
TL;DR: In this article, the authors deal with the theory of hydrodynamic instability and the development of turbulence, the application of dimensional analysis, and the theories of similarity to turbulent flow in pipes, ducts, and boundary layers, as well as free turbulence.
Abstract: This book, originally published in Moscow in 1965, is of interest to a wide scientific and technical audience, including geophysicists, meteorologists, aerodynamicists, chemical, mechanical, and civil engineers--in short, all interested in the fundamental problems of flow, mass, and heat transfer. The authors deal with the theory of hydrodynamic instability and the development of turbulence, the application of dimensional analysis, and the theory of similarity to turbulent flow in pipes, ducts, and boundary layers, as well as free turbulence. They discuss semiempirical theories of turbulence, develop the similarity theory for turbulence in nonhomogeneous media, and present Lagrangian characteristics of turbulence and the theory of turbulent diffusion. Every effort has been made to present a wealth of experimental material; a large number of examples are drawn from physics of the atmosphere, permitting a generalization of results beyond that which can be obtained in the laboratory. Considerable attention has been given to Kolmogorov's theory of the local structure of developed turbulence and to the theory of turbulence in stratified media."Contents: I. Laminar and Turbulent Motion: " Equations of dynamics of a fluid and their most important consequences; Hydrodynamic instability and development of turbulence. "II. Mathematical Methods for Describing Turbulence, Mean Values and Correlation Functions: " Methods for taking mean; The fields of hydrodynamic characteristics regarded as stochastic fields; The moments of hydrodynamic fields. "III. The Reynolds Equation and Semiempirical Theories of Turbulence: " Turbulent flow in pipes and in the boundary layer; Turbulent energy balance and results derived from it. "IV. Turbulence in a Medium Stratified with Respect to Temperature: " Generalization of the theory of the logarithmic boundary layer to the case of a medium stratified with respect to temperature; Comparison of the theory with experimental data on the atmospheric layer near the ground. "V. Motion of Particles (or Elements) in a Turbulent Stream: " Lagrangian description of Turbulence; Turbulent diffusion.
1,164 citations
TL;DR: In this paper, the authors provide an overview of research on the learning and teaching of physics and provide references to meet the needs of two groups of physicists engaged in physics education: the first is the growing number whose field of scholarly inquiry is (or might become) physics education research; the second is the much larger community of physics instructors whose primary interest is in using the results from research as a guide for improving instruction.
Abstract: The purpose of this Resource Letter is to provide an overview of research on the learning and teaching of physics. The references have been selected to meet the needs of two groups of physicists engaged in physics education. The first is the growing number whose field of scholarly inquiry is (or might become) physics education research. The second is the much larger community of physics instructors whose primary interest is in using the results from research as a guide for improving instruction.
620 citations
TL;DR: This paper includes an introduction to JiTT and evidence of its effectiveness, and a discussion of the efforts to disseminate JiTT since it was developed in the 1990s.
Abstract: Just-in-Time Teaching (JiTT) is an innovative method that enables faculty to increase interactivity in the classroom and engage students in learning. By creating a feedback loop between students' work at home and the classroom setting, time on task is improved in both quality and quantity. This paper includes an introduction to JiTT and evidence of its effectiveness. It concludes with a discussion of our efforts to dis- seminate JiTT since it was developed in the 1990's.
301 citations
TL;DR: In this paper, the authors introduce the concept of emergence and the plume mode, and the plate mode, as well as the plate-mode and plume-mode.
Abstract: Part I. Origins: 1. Introduction 2. Emergence 3. Mobility Part II. Foundations: 4. Surface 5. Interior 6. Flow 7. Heat Part III. Essence: 8. Convection 9. Plates 10. The plate mode 11. The plume mode 12. Synthesis IV. Implications: 13. Chemistry 14. Evolution Appendices Index.
297 citations
TL;DR: In this article, the authors used the Force Concept Inventory (FCI) to measure the conceptual learning gain in Studio Physics I for engineers and found that it was a disappointing 0.18±0.12 s.d.
Abstract: In 1993, Rensselaer introduced the first Studio Physics course. Two years later, the Force Concept Inventory (FCI) was used to measure the conceptual learning gain 〈g〉 in the course. This was found to be a disappointing 0.22, indicating that Studio Physics was no more effective at teaching basic Newtonian concepts than a traditional course. Our study verified that result, 〈gFCI,98〉=0.18±0.12 (s.d.), and thereby provides a baseline measurement of conceptual learning gains in Studio Physics I for engineers. These low gains are especially disturbing because the studio classroom appears to be interactive and instructors strive to incorporate modern pedagogies. The goal of our investigation was to determine if incorporation of research-based activities into Studio Physics would have a significant effect on conceptual learning gains. To measure gains, we utilized the Force Concept Inventory and the Force and Motion Conceptual Evaluation (FMCE). In the process of pursuing this goal, we verified the effectiveness...
188 citations
[...]
TL;DR: In this paper, the dynamics of a bouncing ball is described for several common ball types having different bounce characteristics, including tennis balls, a baseball, a golf ball, a superball, a steel ball bearing, a plasticene ball, and a silly putty ball.
Abstract: In this paper, the dynamics of a bouncing ball is described for several common ball types having different bounce characteristics. Results are presented for a tennis ball, a baseball, a golf ball, a superball, a steel ball bearing, a plasticene ball, and a silly putty ball. The plasticene ball was studied as an extreme case of a ball with a low coefficient of restitution (in fact zero, since the collision is totally inelastic) and the silly putty ball was studied because it has unusual elastic properties. The first three balls were studied because of their significance in the physics of sports. For each ball, a dynamic hysteresis curve is presented to show how energy is lost during and after the collision. The measurement technique is quite simple, it is suited for undergraduate laboratory experiments, and it may provide a useful method to test and approve balls for major sporting events.
176 citations
169 citations
TL;DR: The photon correlation spectroscopy (PCS) is a powerful tool for studying the dynamical behavior of fluids near critical points, and a discussion of this phenomenon is given in this paper.
Abstract: By scattering light from small particles, their geometrical structure and their state of motion can be measured. An experiment is described for measuring the diffusivity of small particles undergoing Brownian motion using the technique called photon correlation spectroscopy or dynamic light scattering. The necessary experimental apparatus and the related theory are discussed. Photon correlation spectroscopy is a powerful tool for studying the dynamical behavior of fluids near critical points, and a discussion is given of this phenomenon. The same experimental technique also can be used to study laminar or turbulent flows, and the associated theory is introduced to enable such experiments to be interpreted.
150 citations
TL;DR: This paper found that students who have studied this topic at the introductory level and beyond often cannot account for the pattern produced on a screen when light is incident on a single or double slit.
Abstract: Results from an investigation of student understanding of physical optics indicate that university students who have studied this topic at the introductory level and beyond often cannot account for the pattern produced on a screen when light is incident on a single or double slit. Many do not know whether to apply geometrical or physical optics to a given situation and may inappropriately combine elements of both. Some specific difficulties that were identified for single and double slits proved to be sufficiently serious to preclude students from acquiring even a qualitative understanding of the wave model for light. In addition, we found that students in advanced courses often had mistaken beliefs about photons, which they incorporated into their interpretation of the wave model for matter. A major objective of this investigation was to build a research base for the design of a curriculum to help students develop a functional understanding of introductory optics.
147 citations
TL;DR: The authors surveyed introductory physics students about how they study and how they would advise a hypothetical student to study if she were trying to learn physics deeply with no grade pressure, finding that students perceive trying to understand physics well to be a significantly different activity from "trying to do well in the course".
Abstract: Using written questionnaires, I surveyed introductory physics students about how they study and about how they would advise a hypothetical student to study if she were trying to learn physics deeply with no grade pressure. The survey teases apart students’ “epistemological” beliefs about learning and understanding physics from their more course-specific beliefs about how to earn high grades. The results indicate that students perceive “trying to understand physics well” to be a significantly different activity from “trying to do well in the course.”
TL;DR: In this article, the authors describe how to build an optical tweezer with a total cost of ≈$6500 using only commercially available optics and mounts, and suggest measurements that could be made using the apparatus.
Abstract: Single beam gradient force optical traps, or tweezers, are a powerful tool for a wide variety of experiments in physics, chemistry, and biology. We describe how to build an optical tweezer with a total cost of ≈$6500 using only commercially available optics and mounts. We also suggest measurements that could be made using the apparatus.
TL;DR: In this paper, the authors developed computer programs called PALs (Personal A_ssistants for L_earning) in which computers and students alternately coach each other.
Abstract: Our attempts to improve physics instruction have led us to analyze thought processes needed to apply scientific principles to problems—and to recognize that reliable performance requires the basic cognitive functions of deciding, implementing, and assessing. Using a reciprocal-teaching strategy to teach such thought processes explicitly, we have developed computer programs called PALs (P_ersonal A_ssistants for L_earning) in which computers and students alternately coach each other. These computer-implemented tutorials make it practically feasible to provide students with individual guidance and feedback ordinarily unavailable in most courses. We constructed PALs specifically designed to teach the application of Newton’s laws. In a comparative experimental study these computer tutorials were found to be nearly as effective as individual tutoring by expert teachers—and considerably more effective than the instruction provided in a well-taught physics class. Furthermore, almost all of the students using the PALs perceived them as very helpful to their learning. These results suggest that the proposed instructional approach could fruitfully be extended to improve instruction in various practically realistic contexts.
TL;DR: In this paper, the authors discuss the physics component of the curriculum and describe the impact of the highly collaborative, technology-rich, activity-based learning environment on a variety of conceptual and problem-solving assessments and attitude measures.
Abstract: Over a four-year time span, several departments at North Carolina State University offered experimental sections of courses taken by freshman engineering students. The acronym IMPEC (Integrated Math, Physics, Engineering, and Chemistry curriculum) describes which classes were involved. This paper discusses the physics component of the curriculum and describes the impact of the highly collaborative, technology-rich, activity-based learning environment on a variety of conceptual and problem-solving assessments and attitude measures. Qualitative and quantitative research results indicate that students in the experimental courses outperformed their cohorts in demographically matched traditional classes, often by a wide margin. Student satisfaction and confidence rates were remarkably high. We also noted substantial increases in retention and success rates for groups underrepresented in science, math, and engineering. Placing students in the same teams across multiple courses appears to have been the most beneficial aspect of the learning environment.
TL;DR: In this paper, an inexpensive force plate designed to measure ground reaction forces involved in human movement is presented, which provides interesting demonstrations of relations between displacement, velocity, and acceleration, and illustrate aspects of mechanics that are not normally encountered in a conventional mechanics course, or that are more commonly associated with inanimate objects.
Abstract: Details are given of an inexpensive force plate designed to measure ground reaction forces involved in human movement. Such measurements provide interesting demonstrations of relations between displacement, velocity, and acceleration, and illustrate aspects of mechanics that are not normally encountered in a conventional mechanics course, or that are more commonly associated with inanimate objects. When walking, the center of mass follows a curved path. The centripetal force is easily measured and it provides an upper limit to the speed at which a person can walk. When running, the legs behave like simple springs and the center of mass follows a path that is the same as that of a perfectly elastic bouncing ball.
TL;DR: An introductory guide to the literature on the Casimir force can be found in this article, with references to introductory articles and books, calculations, dynamical Casimir effect, mechanical analogs, applications, and experiments.
Abstract: This resource letter provides an introductory guide to the literature on the Casimir force. Journal articles and books are cited for the following topics: introductory articles and books, calculations, dynamical Casimir effect, mechanical analogs, applications, and experiments.
TL;DR: In this article, the dynamics of a quantum wave packet bouncing on a hard surface under the influence of gravity are studied and the classical limit is discussed and interesting departures from classical behavior are pointed out and explained.
Abstract: The dynamics of a quantum wave packet bouncing on a hard surface under the influence of gravity are studied. This is a system that might be realized experimentally with cold atoms dropped onto an “atomic mirror.” The classical limit is discussed and interesting departures from classical behavior are pointed out and explained.
TL;DR: In this article, the authors explore the character of our understanding of the physical world and of teaching about it, using the culture of science, the set of processes that allow us to build a community consensus knowledge base.
Abstract: Individual teachers of college level physics sometimes develop deep insights into how their students learn and what elements of classroom instruction are valuable in facilitating the learning process. Yet these insights rarely persist beyond the individual instructor. Educational methods seem to cycle from one fad to another, rarely cumulating increasingly powerful knowledge in the way scientists expect understanding to grow. In this paper I explore the character of our understanding of the physical world and of teaching about it. The critical factor is using “the culture of science”—the set of processes that allow us to build a community consensus knowledge base. Elements of the beginning of a base for our educational knowledge are discussed and examples given from discipline-based physics education research.
TL;DR: In this paper, the resistance between two arbitrary nodes in an infinite square lattice of identical resistors is calculated for infinite triangular and hexagonal lattices in two dimensions, and also for infinite cubic and hypercubic lattice in three and more dimensions.
Abstract: The resistance between two arbitrary nodes in an infinite square lattice of identical resistors is calculated. The method is generalized to infinite triangular and hexagonal lattices in two dimensions, and also to infinite cubic and hypercubic lattices in three and more dimensions.
TL;DR: A simple and inexpensive demonstration of acoustic monopole, dipole, and quadrupole sources utilizes four 4-in. boxed loudspeakers and a homemade switch box as mentioned in this paper, which allows the speakers to be driven in any combination of phase relationships.
Abstract: A simple and inexpensive demonstration of acoustic monopole, dipole, and quadrupole sources utilizes four 4-in. boxed loudspeakers and a homemade switch box. The switch box allows the speakers to be driven in any combination of phase relationships. Placing the speakers on a rotating stool allows students to measure directivity patterns for monopole, dipole, and quadrupole speaker combinations. Stacking the speakers in a square, all facing the same direction, allows students to aurally compare the frequency and amplitude dependence of sound radiation from monopoles, dipoles, and quadrupoles.
TL;DR: In this paper, the experimenter can choose between acquiring which-way knowledge and observing an interference pattern at any time, even after the atom has left its mark on the screen.
Abstract: Recently, Mohrhoff [Am. J. Phys. 64, 1468–1475 (1996)] has analyzed a thought experiment of ours [Nature (London) 351, 111–116 (1991)] where a double-slit interferometer for atoms is supplemented by a pair of which-way detectors. Owing to the quantum nature of these detectors, the experimenter can choose between acquiring which-way knowledge and observing an interference pattern. The latter option makes use of a procedure called “quantum erasure.” Mohrhoff (along with other bright colleagues who have made similar statements) claims erroneously that the experimenter has to make this choice before the atom hits the screen. We readdress this issue here and demonstrate that our original assertion was correct: The experimenter can choose between which-way knowledge and quantum erasure at any time, even after the atom has left its mark on the screen.
TL;DR: In this article, a set of tutorials to supplement instruction in a standard calculus-based or algebra-based course on physical optics is presented. But the instructional materials that resulted have proved to be effective at helping students construct and apply a basic wave model for light.
Abstract: This article illustrates the use of research as a basis for the development of curriculum on physical optics. Evidence is presented that university students who have studied physics at the introductory level and beyond often do not have a functional understanding of the wave model for light. Identification and analysis of student difficulties guided the design of a set of tutorials to supplement instruction in a standard calculus-based or algebra-based course. Ongoing assessment was an integral part of the curriculum development process. The instructional materials that resulted have proved to be effective at helping students construct and apply a basic wave model for light.
TL;DR: The capture dynamics is exactly soluble by probabilistic techniques when the number of lions is very small, and is tractable by extreme statistics considerations when the size of the population is very large.
Abstract: We study the capture of a diffusing “lamb” by diffusing “lions” in one dimension. The capture dynamics is exactly soluble by probabilistic techniques when the number of lions is very small, and is tractable by extreme statistics considerations when the number of lions is very large. However, the exact solution for the general case of three or more lions is still not known.
TL;DR: In this paper, the authors compared the performance of different groups of university students in answering a questionnaire designed to probe their understanding of the relationship between macroscopic phenomena of transients in a dc circuit and the microscopic processes that can explain these phenomena.
Abstract: Studies of student understanding of simple electric dc circuits have shown that many of them find it very difficult to apply qualitative reasoning to explain the observed phenomena. It has been suggested that these difficulties may be due to their failure to construct models of microscopic processes that lead to these phenomena. Indeed, in the traditional courses, such models have generally not been emphasized. In the present study, we compared the performance of different groups of university students in answering a questionnaire designed to probe their understanding of the relationship between macroscopic phenomena of transients in a dc circuit and the microscopic processes that can explain these phenomena. One group studied from a traditional text, the second group used a recently developed text that emphasizes models of microscopic processes. We also conducted detailed interviews with some of the students. From an analysis of the performance of these two groups, and also from a comparison with a previous study on Israeli high school students, we found that most of the students whose instructional experiences included an emphasis on the development of models of microscopic processes developed a better understanding of the transient phenomena studied. They applied qualitative considerations in their analyses and were able to develop coherent models to describe their observations. Overall, they demonstrated a superior understanding of the physical phenomena.
TL;DR: In this article, the problem of a vertically thrown ball, with a drag force which is either linear or quadratic in the speed, is discussed. And the equations of motion are solved analytically and several true-to-life examples are discussed.
Abstract: We review the problem of a vertically thrown ball, with a drag force which is either linear or quadratic in the speed. It is stressed from the outset that these two types of drag correspond to specific ranges of the Reynolds number (Re<1 and 103
TL;DR: In this paper, it is shown that the measurement on one oscillator while averaging over the degrees of freedom of the other oscillator without measuring them would yield an increased entropy in the observable oscillator.
Abstract: Coupled harmonic oscillators occupy an important place in physics teaching. It is shown that they can be used for illustrating an increase in entropy caused by limitations in measurement. In the system of coupled oscillators, it is possible to make the measurement on one oscillator while averaging over the degrees of freedom of the other oscillator without measuring them. It is shown that such a calculation would yield an increased entropy in the observable oscillator. This example provides a clarification of Feynman’s rest of the universe.
TL;DR: The authors report on a long-term, large-scale study of a one-semester, conceptually based, introductory astronomy course with data from more than 400 students over three semesters at the University of New Mexico.
Abstract: We report on a long-term, large-scale study of a one-semester, conceptually based, introductory astronomy course with data from more than 400 students over three semesters at the University of New Mexico Using traditional and alternative assessment tools developed for the project, we examined the pre- and postcourse results for Fall 1994, Spring 1995, and Fall 1995 We find our results are robust: novice students show large, positive gains on assessments of conceptual understanding and connected understanding of the knowledge structure of astronomy We find no relationship between course achievement and completion of prior courses in science or math; we do find a small to moderate relationship between students’ science self-image and course achievement Also, we detect little change over each semester in students’ mildly positive incoming attitudes about astronomy and science
TL;DR: In this article, the authors describe the construction and operation of a simple, compact, and cost effective Michelson wavemeter with picometer accuracy, which is used to tune two separate extended cavity diode lasers to achieve two-step excitation of the Rb 52D state, observed by detecting 420 nm blue fluorescence from the 52D→62P→52S decay path.
Abstract: We describe the construction and operation of a simple, compact, and cost effective Michelson wavemeter with picometer accuracy. The low cost of the device means that it can form the basis of an undergraduate laboratory experiment, yet it is sufficiently reliable and accurate that it has become an important tool in our research laboratory, where it is regularly used to tune lasers to atomic transitions. The usefulness and accuracy of the wavemeter is demonstrated by tuning two separate extended cavity diode lasers to achieve two-step excitation of the Rb 52D state, observed by detecting 420 nm blue fluorescence from the 52D→62P→52S decay path.
TL;DR: The work-energy theorem, derived from Newton's second law, applies to the displacement of a particle or the center of mass of an extended body treated as a particle as mentioned in this paper, is not a valid statement about energy transformations when work is done against a frictional force or actions on or by deformable bodies.
Abstract: The work-energy theorem, derived from Newton’s second law, applies to the displacement of a particle or the center of mass of an extended body treated as a particle. Because work, as a quantity of energy transferred in accordance with the First Law of Thermodynamics, cannot be calculated in general as an applied force times the displacement of center of mass, the work-energy theorem is not a valid statement about energy transformations when work is done against a frictional force or actions on or by deformable bodies. To use work in conservation of energy calculations, work must be calculated as the sum of the products of forces and their corresponding displacements at locations where the forces are applied at the periphery of the system under consideration. Failure to make this conceptual distinction results in various errors and misleading statements widely prevalent in textbooks, thus reinforcing confusion about energy transformations associated with the action in everyday experience of zero-work forces such as those present in walking, running, jumping, or accelerating a car. Without a thermodynamically valid definition of work, it is also impossible to give a correct description of the connection between mechanical and thermal energy changes and of dissipative effects. The situation can be simply corrected and student understanding of the energy concepts greatly enhanced by introducing and using the concept of internal energy, that is, articulating the First Law of Thermodynamics in a simple, phenomenological form without unnecessary mathematical encumbrances.
TL;DR: In this paper, the authors explore the manner in which these distributions can arise and how they underlie various scaling laws that play an important role in both random and deterministic systems.
Abstract: Brownian motion represents simple diffusion random walk processes. More complex random walk processes also can occur when probability distributions describing the random jump distances and times have infinite moments. We explore the manner in which these distributions can arise and how they underlie various scaling laws that play an important role in both random and deterministic systems.