bluuebunny/crossref_metadata_2025 huggingface dataset:
Giant magnetoresistance sensors
Authors: Lottis Daniel , Baker Christopher , Pounds Heather
Published: April 2003

We begin by identifying the fascinating behavior of most of the thin, flexible magnets normally described as “refrigerator magnets.” Simple procedures are described that illustrate the intriguing physics of these magnets, which produce fields characterized by spatial variations that are quite abrupt compared to those of the more common ceramic magnets. A method is suggested for producing profiles of this spatial variation. The method is based on the use of magnetic field sensors that employ a novel phenomenon called giant magnetoresistance. After reviewing GMR and the sensors, we describe our field-mapping procedure and discuss the results.
Electrical analog to projectile motion
Authors: Vondracek Mark
Published: April 2003

This article describes an electrical analog to traditional projectile problems given in high school and introductory college classes. It also discusses the importance of stressing the understanding of physical laws and principles to students, and that the physics behind a problem is more important than being able to memorize and use various equations.
A laboratory air-supply system
Authors: Crawford Chuck
Published: April 2003

A practical air-supply system is described for laboratory apparatus such as air tracks and tables using regenerative blower technology. This flexible system is easily constructed and is comparable in cost to commercially available systems. Its advantages include low noise, high reliability, and low maintenance.
Reform in science education: Then and now
Authors: Haber-Schaim Uri
Published: April 2003

In discussions about science education, we often hear and read references to two eras of reform: the first associated with launching of Sputnik in October of 1957 and the second prompted by the publication of Nation at Risk in 1983. Having been deeply involved in the first science project of the first era, namely the Physical Science Study Committee (PSSC) course in physics, now in its seventh edition, and following today's activities closely, I will try to describe the “what's” and “how's” of the PSSC as a representative of the first era and to compare them with today's reform.
Popping bimetal can keep you warm or cool
Authors: Crane H. Richard
Published: April 2003

Crawl out from under the electric blanket, find that the house temperature is just right, pour some hot coffee from the electric percolator and later, in your car, use the turn indicator. Already four times you have enjoyed the benefits of bimetal. You can’t go through a day without it. So what is it?
Happy New Year
Authors: Swartz Clifford E.
Published: April 2003

The rest of the world has calendar years and fiscal years, but we have school years. Summer has done. Happy New Year! New years call for resolutions. Each of us must draw up our own resolutions, but here are some items from my list.
Hey you! Shut the refrigerator door!
Authors: Fay Sarah , Portenga Angela
Published: April 2003

The note discusses electrical power and energy and includes possible labs to be used in a physics classroom. It is based on our experimentation with a new device called the Watt-Watt/Hour Meter, which displays instantaneous power and cumulative energy readings of household electrical devices. Our experiments utilized this meter in conjunction with various appliances and focused primarily on its use with a refrigerator.
Phase-change demonstration—Instant gratification
Authors: Capitolo Mario
Published: April 2003

A suitable vacuum system for use on an overhead projector, students are able to readily see the three phases of water.
Physics teaching and time management
Authors: Di Stefano Rosanne
Published: April 2003

Extensive field tests of four new introductory physics courses, in which the new models were compared with more traditional courses, have yielded many results. The most interesting of these are not directly related to how the new models fared, but instead to general features shared in common by many physics courses. The theme is simply that it is important to set concrete and well-defined goals, and to design every in- and out-of-class activity so that the students’ time is devoted to achieving those goals.
Two-minute impromptu demos
Authors: van den Berg Ed , van den Berg Rosea
Published: April 2003

We present here a collection of small and quick demos that require no equipment beyond what is present in the lecture room (chalk, chairs, students, books, paper, backpacks and their contents). Some are to prove something, but most are to illustrate, visualize, or simulate.
Improved flashbulb demonstration of Faraday’s law
Authors: Sawicki Charles A.
Published: April 2003

A portable Faraday’s law demonstration is described. A rare-earth magnet is dropped down a vertical guide tube passing through a small coil attached to a flashbulb. Reliable flashbulb firing occurs for a magnet fall of 15 cm.
A new twist for the conical pendulum
Authors: Moses Thomas , Adolphi Natalie L.
Published: April 2003

We present a simple experiment using a force sensor to investigate the uniform circular motion of a conical pendulum.
Demonstrating that air is a bad conductor of heat
Authors: McGurk Philip , MacInnes Iain
Published: April 2003

Here is a quick and inexpensive way to demonstrate to your class that air is a poor conductor of heat, using an aluminum beaker and a soda can over a Bunsen burner.
Deconstructing a plasma globe
Authors: Guilbert Nicholas R.
Published: April 2003

The plasma globe employs ideas from plasma physics, spectroscopy, atomic structure, and electronics, among other areas. This article explores some of the physics behind the plasma globe and suggests some student investigations.
Spreadsheet waves
Authors: Haugland Ole Anton
Published: April 2003

Modern spreadsheets have very powerful graphics capabilities. We used a spreadsheet to simulate the motion of wave pulses along a rope.
Teaching physics with math to weak math students
Authors: Vondracek Mark
Published: April 2003

This note describes a teaching strategy in physics classes that has large numbers of students who are weak in math, particularly basic algebra. Typically these students have low self-confidence in their physics work and are intimidated by physics equations. The strategy discussed here helps even the weakest students gain confidence and allows them to solve standard physics problems after several days, and teachers can add mathematical problems to what may have been a strictly conceptual physics class.
Henry Cavendish and the density of the earth
Authors: Lally Sean P.
Published: April 2003

From the fall of 1797 through the spring of 1798, Henry Cavendish performed a series of experiments, which now bear his name, that were aimed at determining the density of Earth. While Cavendish is rightfully considered a brilliant experimenter by many historians, he is often credited (in both popular and historical literature) as the scientist who first accurately weighed the Earth and determined the universal constant of gravitation, G. While the universal constant of gravitation and the mass (or weight) of the Earth can indeed be calculated from the density of the Earth, this was neither Cavendish's result nor his intent in writing “Experiments to Determine the Density of the Earth.” Rather, Cavendish's interest lies in solving an eighteenth-century dispute: what is the mean density of the Earth?
The speed of sound in air as a function of temperature
Authors: Worland Rand S. , Wilson D. David
Published: April 2003

We describe an undegraduate experiment in which the speed of sound in air is measured at temperatures ranging from 250 to 335 K. We discuss the experimental methods used to make the measurements and compare the results with theory. The pedagogical advantages of this conceptually simple experiment are also discussed.
What does a pine cone tell us about humidity?
Authors: Silva Larry , Beiting Daniel
Published: April 2003

The influence of the humidity in the air on the shape of a pine cone is examined. This simple research project helps undergraduate students discover how useful analogies can be in extrapolating the physics they know toward new areas they are trying to understand.
Rubber-band-driven airplane contest
Authors: Oliver Douglas , Ng Terry
Published: April 2003

In this note a design competition is proposed where students are given an off-the-shelf rubber-band-driven model airplane. They are to use the principles of aerodynamics to alter the design of the plane to carry cargo over extended distances. Project has been used successfully with large groups of students at both primary and secondary grade levels. Idea would also serve for a science club activity.
A moment of reflection
Authors: Bouffard Karen
Published: April 2003

This fourth Olympics column has two activities based on the concept of reflection. This second activity uses four mirrors to “hit” a target with a laser beam. This activity turns out to be more instructive than others we have used employing lenses and prisms.
Meet your new president: Larry Kirkpatrick
Authors: Wheeler Gerry
Published: April 2003

Gerry Wheeler introduces the 1999 AAPT President, Larry Kirkpatrick of Montana State University.
The buzzing of flies’ wings
Authors: Easton Don
Published: April 2003

The object of this science-fair project was to determine the wing-beat frequency of common house flies from the frequency of the sound produced when they buzz their wings. The data produced a pattern that I have seen many times and felt sure that I knew what was going on. Like many interesting and seemingly simple phenomena, the longer that I look at this one the more intriguing and less explicable it becomes.
Innovations in physics teaching—A cautionary tale
Authors: Mottmann John
Published: April 2003

Do innovations in physics education really result in an improvement of students’ abilities or attitudes? Anecodotal observations of my institution’s efforts do not confirm any obvious gains.
Curious celts and riotous rattlebacks
Authors: Edge Ronald D. , Childers Richard
Published: April 2003

Rattlebacks, or celts, are curiously shaped objects, which, when spun in one direction, will stop, rock sideways, reverse, and spin in the opposite direction. We made a simpler version with a plastic spoon from a fast-food restaurant.
Specialists
Authors: Swartz Clifford E.
Published: April 2003

Whether in high school or college, the teacher is expected to be a dual specialist in the subject matter and in the application of the teaching process. Good teachers are like good specialists; they may not know why the system works, but they do know how to make it work.
Experiences of a web-page user
Authors: Harris, C.F.C. Robert W.
Published: April 2003

This article recounts the author’s experience building a physics site on the World Wide Web and using the site with a high school pnysics class.
The neon sign
Authors: Sampere Samuel M.
Published: April 2003

What are a crumpled 55-gallon steel barrel and a tavern-style neon sign doing in the hallway of the physics building at a renowned and revered educational institution? It’s attracting attention, stopping people in their tracks, and sending a message: physics is about size and color, motion and interaction; it’s fun and it’s interesting, something to experience for yourself.
A thermometer whose memory is a one-sided magnet
Authors: Crane H. Richard
Published: April 2003

Recently I described an out-of-doors thermometer that works with bimetal. It remembers both the highest and lowest excursions, and it is easily reset. And I recalled that very long ago I had seen quite a different kind, a mercury one, but I could not reconstruct how it was done. Then along came a catalog that showed a mercury one. Of course I ordered one, and did reverse engineering on it. It will have some things to add to your bag of tricks.
Solving a problem by analogy
Authors: Easton Don
Published: April 2003

This note is a description of a student solution to a problem. I found the solution exciting because it exemplifies the kind of solution by analogy that Feynman describes in The Feynman Lectures on Physics.
An F=ma analysis of the spinning skater and decaying satellite orbit
Authors: Arons Arnold
Published: April 2003

Spinning skaters and satellite orbits are usually discussed in terms of angular momentum and other powerful formalisms. This paper presents an alternative, more primitive analysis based directly on Newton’s second law.
Measuring equilibrants with a bracket-mounted force sensor
Authors: Kingman Robert , Maddox David
Published: April 2003

One of the important concepts in introductory physics is vectors and their addition. We have developed a method that restores simplicity to teaching the idea of adding several forces, and does it with an experimental error of one percent or less.
Long-distance free fall
Authors: Gallant Joseph , Carlson James
Published: April 2003

We present an analysis of a situation described in Milton’s epic poem “Paradise Lost” in which we calculate the distance required for a nine-day free-fall from rest to the Earth. The resulting method is completely general, and can be applied to free-fall toward other bodies and to near-Earth free-fall as well.
Demonstrating angular momentum conservation
Authors: Carr Robert , Cohen Harold , Ragsdale Terry
Published: April 2003

We have designed and constructed apparatus for our laboratory program with which students can measure angular momentum and demonstrate its conservation to a high degree of precision.
A chaotic pendulum
Authors: Oliver Douglas
Published: April 2003

This article describes how you can assemble an inexpensive magnetic chaotic oscillator that can be manipulated and reconfigured by students.
A visual and acoustic demonstration of beats and interference
Authors: Boucher Derrick E.
Published: April 2003

A method to demonstrate interference and beats using two audio signal generators, a stereo audio system, and an optional dual-trace oscilloscope is presented. This method is well suited to large lectures because the sound is loud, it can be continued for an indefinite period of time, and the effect can be adjusted during the demonstration.
Music to teach astronomy by
Authors: Möbius Eberhard
Published: April 2003

Author shares his technique of aligning music selections with his introductory astronomy syllabus. He begins class with a music selection as an introduction to the concepts covered in class. List of 40 music titles and composers used can be downloaded from http://www-ssg.sr.unh.edu/406/music.html.
MacGyver’s desert adventure
Authors: Bouffard Karen
Published: April 2003

Television’s government agent MacGyver used his arcane knowledge of science to get out of seemingly hopeless situations. I find the challenge presented in this column to be a good assessment for our unit on “heat.”
Coalescence of raindrops in an electrostatic field
Authors: Jermacans Kara , Laws Kenneth
Published: April 2003

Small cloud droplets grow to large raindrops by the coalescence resulting from collisions. It can be demonstrated, both theoretically and by a vivid demonstration, that this collision/coalescence process is aided by the electrostatic fields found in thunderstorms.
Weight—An accurate, up-to-date, layman’s definition
Authors: Bishop Roy
Published: April 2003

The conventional definition of weight presented in physics textbooks is not what is popularly meant by weight, causes needless confusion in weightless situations, and is based upon a pre-1915 theory of gravitation. Arguments are presented in favor of a better definition.
Energy considerations in a vertical spring
Authors: Esparza-Barrera Carlos
Published: April 2003

Here is an interesting relationship between initial and final mechanical energy of a simple system that is subject to friction.
Modeling energy outflow in stars
Authors: Zeilik Michael
Published: April 2003

Do your students have difficulty visualizing how photons travel out of the Sun? Over 20 years, I have tried different ways to help students conceptualize a random walk, including computer simulations. But the method I found works the best with a wide range of students is a physical one that uses a clever toy: a Bumble Ball™
Welcome to physics
Authors: Rylander Jeffrey W.
Published: April 2003

This note presents a first-day activity and demonstration to introduce physics as the study of patterns in nature.
Fermi questions
Authors: Bouffard Karen
Published: April 2003

This column contains problems and solutions for the general category of questions known as “Fermi” questions. Forcing the students to use their ability to estimate, giving answers in terms of order-of-magnitude, is not only a challenge for a competition, but a teaching strategy to use in the classroom to develop self-confidence and the ability to analyze answers as to whether or not they make sense, as opposed to relying on the “precision” of a calculator value.
A lesson in curve fitting
Authors: Calvin Scott
Published: April 2003

An exercise is presented in which temperature data for New York City is fit to a sinusoidal model and then extrapolated to later times. This exercise requires students to demonstrate understanding of how physical constraints enter into curve fitting.
Detecting the polarity of an electric charge
Authors: Chen Xiang Yong , Wang Xing
Published: April 2003

In experiments on electrostatics, we often obtain charge by friction or induction. How do we determine the polarity? Is the static electric charge positive or negative? We can solve the questions with a small neon tube.
Hands-on magnetic field measurements with a GMR sensor
Authors: Priest Joseph
Published: April 2003

Magnetic field sensors based on giant magnetoresistance (GMR) are becoming increasingly useful in laboratory exercises for students taking a beginning course in electromagnetism. We describe three simply conceived, hands-on exercises involving magnetic field measurements that require only a GMR sensor, a 5-V power supply, and a voltmeter having millivolt accuracy.
Measuring the diameter of your blind spot
Authors: Sanny Jeff
Published: April 2003

A simple experiment to determine the diameter of the blind spot is described. Students are divided into groups of three and work together to perform the experiment. The procedure takes about 15 minutes and seems to be quite enjoyable to the class.
Vectoring backwards
Authors: Schultz Frederick H. C.
Published: April 2003

From the 50 years I taught college physics, I have the memory of one perfect demonstration. It was unplanned, unrepeatable, and 100% successful. It will never be forgotten by me and probably not by any of the fellows who were in the class.
Cooperative learning: An inside story
Authors: Andre Kathleen M.
Published: April 2003

Cooperative learning is one innovative technique used in an engineering physics course at Ohio State. Student opinions on the cooperative element were solicited near the end of the course. These comments provide useful insight into why students believe cooperative learning is helpful in learning physics.
Folded-path doppler and the measurement of blood flow
Authors: Crane H. Richard
Published: April 2003

Everyone who has listened to a train go by while blowing its whistle has heard the Doppler frequency shift. The practical problem is finding the velocity of something moving at some distance that neither transmits nor receives.
More Fermi questions
Authors: Bouffard Karen
Published: April 2003

“Fermi” questions are a popular component of most Physics Olympics meets. Asking students to make a reasonable assumption about a problem and give answers in terms of order of magnitude is not only a great challenge for a competition, but is also a valued teaching strategy in the classroom.
Raw eggs—moving target
Authors: Forrest Doug
Published: April 2003

High school physics students often have difficulty with understanding when and where to use an appropriate calculation to solve a problem. In this activity students have to solve a real problem using formulas they have seen before, but in a context with which they are unfamiliar; namely dropping a raw egg on a moving target—their instructor.
Visualizing displacement current—A classroom experiment
Authors: Rizzotto Marcos G.
Published: April 2003

In this work we present a simple experiment to introduce the concept of displacement current. It can be done in an undergraduate physics course with standard electronics available in a teaching laboratory.
A strange behavior of friction
Authors: Morrow Rebecca , Grant Alistair , Jackson David P.
Published: April 2003

We investigate the effects of dry, sliding friction between a felt-covered wood block and a wooden table. By measuring the applied force and the acceleration of the block, we experimentally determine the force of kinetic friction and find that it is constant when the applied force is larger than a terminal frictional force Ft=μtmg. However, we also find that the block continues to move without decelerating when the applied force is less than Ft. This strange behavior contradicts the common notion that the force of kinetic friction is constant and depends only on the normal force.
Centrifugal force and friction
Authors: Larson Roger F.
Published: April 2003

A rotary motion probe is used to first measure the angle at which a washer overcomes static friction so that the coefficient of static friction can be calculated from the μ=tanθ, relationship. The force of friction between the washer and a metal rod is then equated with the centrifugal force required to overcome the static friction between the washer and a rod undergoing angular acceleration. From this equality the theoretical velocity at which the washer begins to slide off of the rod is calculated. The theoretical velocity is then compared to the velocity for this occurrence as measured with rotary motion probe.
Demonstrations of Coulomb’s law with an electronic balance
Authors: Cortel Adolf
Published: April 2003

The demonstrations use an electronic balance to measure the electric force between two charged balls. The values of the force and the distance fit to a function type F∝db in good agreement with Coulomb's law. This setup also allows demonstrating that the force is proportional to the electrical charge. The electrostatic induction between a charged and a neutral ball can be observed as well.
Rayleigh-Taylor instability–fascinating gateway to the study of fluid dynamics
Authors: Benjamin Robert F.
Published: April 2003

A series of low-cost simple, “kitchen-physics” experiments demonstrates Rayleigh-Taylor Instability (RTI), the growth of ripples at an interface between fluids when the higher-density fluid is on top. We also describe the importance of RTI in ocean dynamics and commercial products.
Power requirements for rollerblading and bicycling
Authors: Waltham Chris , Copeland Brian
Published: April 2003

This article describes a simple analysis of two common modes of human-powered locomotion—rollerblading and bicycling. Straightforward measurement techniques are used to understand the types of opposing force encountered. Practical and pedagogical implications are examined.
On the merits of “Unusual Field Trips”
Authors: Howarth Dean E.
Published: April 2003

This note is a synopsis of an “unusual field trip” (as it is categorized by our county’s office of risk management) taken by a group of physics students to New Mexico during their 1998 spring break. On our four-day trip we visited points of scientific interest related to the Manhattan Project and astronomy.
The asymmetrical “sticking” behavior of two balls on an incline
Authors: Mallinckrodt A. John
Published: April 2003

After a question from Dindorf [see Phys. Teach. 37, 184 (March 1999)], I examined the conditions for static equilibrium of two balls in contact on an incline. The results reveal the source of the interesting asymmetry that is observed in the “sticking” behavior of the two balls.
A note on quantum teleportation
Authors: Sawicki Mikolaj
Published: April 2003

Ever since the first successful Quantum Teleportation experiment was performed at the University of Innsbruck and subsequently repeated by numerous groups worldwide, the subject of Quantum Teleportation has been a big hit not only in the physics journals, but even more so in mass media.
Constructing a celestial calendar wheel
Authors: Cousineau Sarah M.
Published: April 2003

When we are asked to consider astronomical monuments of historical significance, we often think of Stonehenge, Mayan cities, or Aztec calendars. Few of us in the United States are prompted to look in our own backyard, where Native Americans spent centuries monitoring the rhythmic motions of the skies.
A short course on observational astronomy
Authors: Thompson Richard J.
Published: April 2003

This note describes an experimental course carried out in collaboration between a small liberal arts university and a private research foundation which exposes students to the many aspects of astronomical research, including planning and carrying out a three-day observing trip and analyzing the acquired data.
Additions to a circular-motion lab
Authors: Jameson Bill
Published: April 2003

Building on a previous Apparatus article, some additions to a circular motion lab allow quick, accurate determination of the mathematical model F=mv2/R. Using a force probe and motion detector interfaced to a computer, data is quick and easy to acquire
Mechanics in a wheelchair
Authors: Bernhard Karin , Bernhard Jonte
Published: April 2003

It is not only possible for a student sitting in a wheelchair to participate in many active engagement activities. Using a wheelchair is also of extra value for non-physically disabled students in many experiential mechanics activities since the friction is low and kinesthetic experience involved. A wheelchair can also be used as an engaging “tool” for connecting mechanical concepts and real-world phenomena.
Stellar bar codes
Authors: Adams Jeff , Slater Tim
Published: April 2003

This note describes an inquiry-based collaborative group activity that allows students to discover the connection between stellar spectra and temperatures using simulated stellar spectra.
More fun with singing wineglasses
Authors: Planinsic Gorazd
Published: April 2003

A novel phenomenon in the titled resonating wineglass is described and explained qualitatively. A method for presentation of wineglass vibration with conventional overhead projector is described.
Pendulum period versus hanging-spring period
Authors: Holzwarth David E. , Malone Jim
Published: April 2003

We introduce the vocabulary of wave phenomena using both a pendulum and a mass oscillating at the end of a spring. One day, after going through the various characteristics of both systems, just for the sake of curiosity I asked the students to figure out a way to match the periods of the two systems.
Another way to demonstrate Lenz’s law
Authors: Ivanov Dragia T.
Published: April 2003

An accessible demonstration of Lenz’s law is offered in which the effect of the retarded sliding of a ring magnet on an inclined aluminum plate is observed. The experiment is done on the basis of comparison and includes the explanation of the effect.
Cotton buds, momentum, and impulse
Authors: van den Berg Ed , Nuñez Jover , Guirit Alfredo , van Huis Cor
Published: April 2003

Here is a simple experiment demonstrating impulse and momentum that was picked up from a Japanese presenter at a physics teacher conference held in Cebu City. We have not been able to trace the experiment farther and have never seen it in print. After student-author Nuñez demonstrated it during an exam on conducting demonstrations, we converted the qualitative idea into a quanitative experiment and even discovered some possibilities for student research. The lab is also suitable as homework, since it uses universally available ”equipment“ — cotton buds (swabs), drinking straws, and a ruler.
Babies and the moon
Authors: Toepker Terrence P.
Published: April 2003

“More babies are born under a full moon than at any other time.” Many of us have heard this assertion, and a few years ago I tried to get data that would support it. The note “A Lesson in Curve Fitting” by Scott Calvin (Phys. Teach. 37, 340, Sept. 1999) provoked me to pass some of the data on to readers of The Physics Teacher.
Avogadro’s number and the kinetic theory of gases
Authors: Bryan Ronald
Published: April 2003

Since the rms speed vrms of gas molecules in a container does not depend on the number of molecules but only on the pressure, the volume, and the total mass of the gas, Bernoulli probably knew that his kinetic theory required an atmospheric vrms is approximately equal to 1100 mi/hr at STP. Concerns over such a high speed were no doubt lessened with measurement of Avogardo’s number some 170 years later.
Politics Weighs on the physics student
Authors: Vaquero José M.
Published: April 2003

Even though a textbook is a historical document because it contains the science and pedagogy of its author and the times, its “weight” can be daunting for the student.
Seeking the holy grail of teaching
Authors: Higbie Jack
Published: April 2003

Twenty-eight years of university teaching has taught me that wanting to be a good teacher and trying very hard to be a good teacher does not necessarily make one a good teacher. I tried many strategies and hardly a year went by that I did not completely rewrite my lecture notes or change textbooks in search of a more lucid presentation. At the end I was still eager to try yet another approach, which just might work this time.
Meet your new President: Ruth Howes
Authors: Watson Jim
Published: April 2003

Jim Watson introduces the 2000 AAPT President, Ruth Howes of Ball State University.
Head noises
Authors: Senior Tom
Published: April 2003

Students turned their ears into speakers with the aid of an inexpensive toy called “Sound Bites.” With this device they have a startling introduction to vibrations, sound waves, electrical signals, and transducers.
Buzzwords and newspeak
Authors: Swartz Clifford E.
Published: April 2003

You have to read beneath the lines in this business. Every week I get manuscripts filled with words and phrases fraught with cabalistic meaning. Would you believe, for instance, that in using the modeling method of teaching that the carefully structured development and concept flow would lead through Socratic dialogue to a rich classroom discourse? Perhaps it would help if I reminded you that a model is a primary unit of coherently structured knowledge. Of course, I am speaking only of the essence of models that are at the heart of modeling theory. These depend on student-centered teaching that is research-informed, leading to interactive engagement methods and cooperative learning.
Equivalent mass of a coil spring
Authors: Ruby Lawrence
Published: April 2003

The Hooke’s law force on a coil spring often constitutes a student’s first introduction to the properties of simple harmonic motion. The usual treatment assumes a vertical massless spring, held fixed at one end and stretched by a hanging mass M at the other. An occasional text, however, points out that the treatment, in the case of a hanging spring, can be improved by taking into account the equivalent mass mo/3 of the spring. It is only necessary to addmo/3 to the hanging mass M in the expression that relates the frequency of the spring oscillations to M and to the spring constant k.
Demonstrating the relationship between the energy and frequency of light
Authors: Cortel Adolf
Published: April 2003

The spectrum produced by a slide projector with an inexpensive diffraction grating illuminates a screen that is partially covered by a phosphorescent strip. Only photons with the highest energies/frequencies, including near UV, produced phosphorescence.
Magnification ratio and the lens equations
Authors: Lawrence Robert W.
Published: April 2003

The calculation for the locations of the conjugate foci of an object and its image is simplified by stating distances in “focal lengths” and utilizing the magnification ratio as a parameter in the lens equation. Forms of the equation are developed from both the familiar Gaussian as well as the older Newtonian equation.
The speed of light with a shortwave radio
Authors: Beaver John E.
Published: April 2003

We have recorded standard time signals transmitted simultaneously by the two National Institute of Standards and Technology broadcast stations in Colorado and Hawaii. By measuring the difference in arrival times of these two signals (as received in Wisconsin) students can determine the speed of light.
Physical principles versus mathematical rigor
Authors: Patterson Jim
Published: April 2003

A kinematics problem in which a ball is thrown into the air and a second ball is dropped sometime later is presented. The solution is simplified by close attention to the mathematical details, and the physical significance of the resulting function is discussed.
Using wind chimes to introduce the physics course
Authors: Harris Robert W.
Published: April 2003

This article recounts the author’s experience using wind chimes to teach the scientific method including significant figures, experimental error, types of variation, peer review of results, seeking empirical relationships within data, and testing the relations found.
Easily constructed mini-sextant demonstrates optical principles
Authors: Nenninger Garet G.
Published: April 2003

An easily constructed optical instrument for measuring the angle between the Sun and the horizon is described. The miniature sextant relies on multiple reflections to produce multiple images of the sun at fixed angles away from the true Sun.
Finding Kepler’s third law with a graphing calculator
Authors: Metz James
Published: April 2003

Johannes Kepler (1571-1630) struggled to learn the relationship between the period (T) and the radius (R) of the orbit of the planets, but today’s students can easily determine this relationship using a graphing calculator.
The ether wind and the global positioning system
Authors: Müller Rainer
Published: April 2003

In this article, we give a simple illustration how and why GPS (Global Positioning System) navigation would be affected by a possible ether wind. With a qualitative analysis of the navigation process, we can estimate how big the discrepancy between the GPS receiver’s inferred position and its true position would be. In addition, a one-dimensional quantitative model is discussed that leads to the same conclusion.
On teaching—Innovative and traditional
Authors: Hilborn Robert C.
Published: April 2003

John Mottmann’s article in the February 1999 issue of The Physics Teacher raises a number of important issues concerning innovations in introductory physics teaching. I want to focus on the underlying assumptions in Mottmann’s commentary since those assumptions appear quite frequently when dedicated teachers defend what they call “the traditional lecture mode” of teaching. For anyone concerned about fostering improvements in physics teaching, it is important to uncover those assumptions and to understand what lies behind them.
Resonant wineglasses and Ping-Pong™ balls
Authors: Berner Bill
Published: April 2003

There must have been a moment, after Caruso but before Ella Fitzgerald, when the standard measure for sound power was not the breaking of glass. Clearly that moment has passed, and this strong public image presents a great opportunity for physics demonstrations. The fact that you see so few teachers (and tenors) breaking glasses might be an indication of the practical difficulty in executing this simple concept. But with today’s audio technology, and a Ping-PongTM ball, many things are possible.
Is Maxwell’s displacement current a current?
Authors: French A. P.
Published: April 2003

A recent TPT article describes an experiment in which a toroidal coil is placed between the plates of a capacitor that is connected to an alternating voltage source. An alternating voltage signal is developed between the ends of the toroid. It is often claimed that such an experiment demonstrates the magnetic field produced by Maxwell’s displacement current. The purpose of this note is to examine that claim. The key question is: Does the displacement current act as a source of magnetic field in the same way as a current in a wire? Our answer — although it is not new — may surprise some readers.
Magnetic deflection demonstrator
Authors: Capitolo Mario , Lonc William
Published: April 2003

A very low cost magnetic deflection demonstration apparatus is easily built from a typical oscilloscope. The apparatus could replace relatively expensive replacement parts of “classical” apparatus.
Posing Einstein’s question: Questioning Einstein’s pose
Authors: Topper David , Vincent Dwight E.
Published: April 2003

The paper deals with different versions and variations of a famous photograph of Einstein. It sets the historical background for the picture and explains the meaning of the equation on the blackboard in terms of Einstein’s thinking in 1931.
Instantaneous impulses
Authors: Erlichson Herman
Published: April 2003

In our physics course for liberal-arts students, “Galileo to Newton and Beyond,” students read literature of the period and do many experiments that relate directly to the history of physics. One such experiment concerns instantaneous impulses, where we extend Newton’s instantaneous-impulse method of orbital analysis to a graphical method of orbit determination. We have found that this experiment does a good job of teaching both horizontal projectile motion and instantaneous impulse.
The flow of sand
Authors: Yersel Metin
Published: April 2003

Dimensional analysis is used to obtain an expression for the mass flow of sand through varying sized orifices. Measurements on flow rates as a function of orifice size are made to investigate the validity of the dimensional assumptions.
A modern Kelvin balance for undergraduate experimentation
Authors: Rockefeller Alexandra , Graf Erlend H.
Published: April 2003

An apparatus suitable for the study of electrostatic forces by physics undergraduates is described. By using an electronic scale to measure the force between the plates of a charged capacitor, students can verify the inverse square exponent of Coulomb’s law and check the value of the permittivity of air to an accuracy of 1-2 percent.
Demonstrating forces between parallel wires
Authors: Baker Blane
Published: April 2003

A simple, highly effective demonstration of mutual repulsion (attraction) between parallel conductors is described for the classroom. The physical effects are clearly elucidated using readily available materials in conjunction with a high-current (20 A) dc power supply.
Seeing infrared
Authors: McFarland Ernie , Kehn Tom
Published: April 2003

The infrared signals emitted by a remote control can be “seen” if the remote is pointed at an infrared-sensitive photocell connected to an oscilloscope.
Addressing physical intuition—A first-day event
Authors: Keeports David
Published: April 2003

I present some ideas concerning the sources and limitations of human physical intuition, which I have included in the introductory lectures of my general physics courses.
Recognition of Paleoearthquakes on the Puente Hills Blind Thrust Fault, California
Authors: Dolan James F. , Christofferson Shari A. , Shaw John H.
Published: April 2003

Borehole data from young sediments folded above the Puente Hills blind thrust fault beneath Los Angeles reveal that the folding extends to the surface as a discrete zone (≤145 meters wide). Buried fold scarps within an upward- narrowing zone of deformation, which extends from the upward termination of the thrust ramp at 3 kilometers depth to the surface, document the occurrence of at least four large (moment-magnitude 7.2 to 7.5) earthquakes on this fault during the past 11,000 years. Future events of this type pose a seismic hazard to metropolitan Los Angeles. Moreover, the methods developed in this study can be used to refine seismic hazard assessments of blind thrusts in other metropolitan regions.
Mitosis Through the Microscope: Advances in Seeing Inside Live Dividing Cells
Authors: Rieder Conly L. , Khodjakov Alexey
Published: April 2003

The most visually spectacular events in the life of a cell occur when it divides. This is especially true in higher eukaryotes, where the size and geometry of cells allow the division process to be followed through a microscope with considerable clarity. In these organisms, the membrane surrounding the nucleus breaks down after the replicated DNA has condensed to form discrete chromosomes. Several new structures are then assembled to separate the chromosomes and partition the cytoplasm into two separate cells.
Development and Use of Fluorescent Protein Markers in Living Cells
Authors: Lippincott-Schwartz Jennifer , Patterson George H.
Published: April 2003

The ability to visualize, track, and quantify molecules and events in living cells with high spatial and temporal resolution is essential for understanding biological systems. Only recently has it become feasible to carry out these tasks due to the advent of fluorescent protein technology. Here, we trace the development of highly visible and minimally perturbing fluorescent proteins that, together with updated fluorescent imaging techniques, are providing unprecedented insights into the movement of proteins and their interactions with cellular components in living cells.
Gating the Selectivity Filter in ClC Chloride Channels
Authors: Dutzler Raimund , Campbell Ernest B. , MacKinnon Roderick
Published: April 2003

ClC channels conduct chloride (Cl
–
) ions across cell membranes and thereby govern the electrical activity of muscle cells and certain neurons, the transport of fluid and electrolytes across epithelia, and the acidification of intracellular vesicles. The structural basis of ClC channel gating was studied. Crystal structures of wild-type and mutant
Escherichia coli
ClC channels bound to a monoclonal Fab fragment reveal three Cl
–
binding sites within the 15-angstrom neck of an hourglass-shaped pore. The Cl
–
binding site nearest the extracellular solution can be occupied either by a Cl
–
ion or by a glutamate carboxyl group. Mutations of this glutamate residue in
Torpedo
ray ClC channels alter gating in electrophysiological assays. These findings reveal a form of gating in which the glutamate carboxyl group closes the pore by mimicking a Cl
–
ion.
For the Insect Pathogen
Photorhabdus luminescens
, Which End of a Nematode Is Out?
Authors: Ciche Todd A. , Ensign Jerald C.
Published: April 2003

The nematode
Heterorhabditis bacteriophora
is the vector for transmitting the entomopathogenic bacterium
Photorhabdus luminescens
between insect larvae. The dauer juvenile (DJ) stage nematode selectively retains
P. luminescens
in its intestine until it releases the bacteria into the hemocoel of an insect host. We report the results of studying the transmission of the bacteria by its nematode vector. Cells of
P. luminescens
labeled with green fluorescent protein preferentially colonized a region of the DJ intestine immediately behind the basal bulb, extending for various distances toward the anus. Incubation of DJ nematodes in vitro in insect hemolymph induced regurgitation of the bacteria. Following a 30-min lag, the bacteria migrated in a gradual and staggered movement toward and ultimately exited the mouth. This regurgitation reaction was induced by a low-molecular-weight, heat- and protease-stable, anionic component present in arthropod hemolymph and in supernatants from insect cell cultures. Nematodes anesthetized with levamisole or treated with the antihelmenthic agent ivermectin did not release their bacteria into hemolymph. The ability to visualize
P. luminescens
in the DJ nematode intestine provides the first clues to the mechanism of release of the bacteria during infection of insect larvae. This and the partial characterization of a component of hemolymph triggering release of the bacteria render this fascinating example of both a mutualistic symbiosis and disease transmission amenable to future genetic and molecular study.
Absence of Malolactic Activity Is a Characteristic of H+-ATPase-Deficient Mutants of the Lactic Acid BacteriumOenococcus oeni
Authors: Galland Delphine , Tourdot-Maréchal Raphaëlle , Abraham Maud , Chu Ky Son , Guzzo Jean
Published: April 2003

The lack of malolactic activity in H+-ATPase-deficient mutants ofOenococcus oeniselected previously was analyzed at the molecular level. Western blot experiments revealed a spot at 60 kDa corresponding to the malolactic enzyme only in the parental strain. Moreover, themleAtranscript encoding the malolactic enzyme was not detected by reverse transcription (RT)-PCR analysis of mutants. These results suggest that the malolactic operon was not transcribed in ATPase-deficient mutants. ThemleRgene encoding a LysR-type regulatory protein which should be involved in expression of the malolactic genes was described previously forO. oeni. Results obtained in this study show that themleRtranscript was not detected in the mutants by RT-PCR. No mutation in the nucleotide sequences of themleRgene and the malolactic operon was found. The effect of a reduction in H+-ATPase activity onl-malate metabolism was then investigated by using other malolactic bacteria. Spontaneous H+-ATPase-deficient mutant strains ofLactococcus lactisandLeuconostoc mesenteroideswere isolated by using neomycin resistance. Two mutants were selected. These mutants exhibited ATPase activities that were reduced to 54 and 70% of the activities obtained for theL. lactisandL. mesenteroidesparental strains, respectively. These mutants were also acid sensitive. However, in contrast to the ATPase-deficient mutants ofO. oeni, activation ofl-malate metabolism was observed with theL. lactisandL. mesenteroidesmutants under optimal or acidic growth conditions. These data support the suggestion that expression of the genes encoding malolactic enzymes inO. oeniis regulated by themleRproduct, as it is inL. lactis. Nevertheless, our results strongly suggest that there is a difference between the regulation of expression of the malolactic locus inO. oeniand the regulation of expression of this locus in less acidophilic lactic acid bacteria.
Identification of
Lactobacillus reuteri
Genes Specifically Induced in the Mouse Gastrointestinal Tract
Authors: Walter Jens , Heng Nicholas C. K. , Hammes Walter P. , Loach Diane M. , Tannock Gerald W. , Hertel Christian
Published: April 2003

Lactobacilli are common inhabitants of the gastrointestinal tracts of mammals and have received considerable attention due to their putative health-promoting properties. Little is known about the traits that enhance the ability of these bacteria to inhabit the gastrointestinal tract. In this paper we describe the development and application of a strategy based on in vivo expression technology (IVET) that enables detection of
Lactobacillus reuteri
genes specifically induced in the murine gut. A plasmid-based system was constructed containing ′
ermGT
(which confers lincomycin resistance) as the primary reporter gene for selection of promoters active in the gastrointestinal tract of mice treated with lincomycin. A second reporter gene, ′
bglM
(β-glucanase), allowed differentiation between constitutive and in vivo inducible promoters. The system was successfully tested in vitro and in vivo by using a constitutive promoter. Application of the IVET system with chromosomal DNA of
L. reuteri
100-23 and reconstituted lactobacillus-free mice revealed three genes induced specifically during colonization. Two of the sequences showed homology to genes encoding xylose isomerase (
xylA
) and peptide methionine sulfoxide reductase (
msrB
), which are involved in nutrient acquisition and stress responses, respectively. The third locus showed homology to the gene encoding a protein whose function is not known. Our IVET system has the potential to identify genes of lactobacilli that have not previously been functionally characterized but which may be essential for growth of these bacteria in the gastrointestinal ecosystem.