bluuebunny/crossref_metadata_2025 huggingface dataset:
How dense is a black hole?
Authors: Lo Presto Michael C. , Meroueh Rima
Published: April 2003

Since the discussion of black holes in introductory astronomy is usually preceded by a discussion of white dwarfs and neutron stars, increasing density is usually a recurring theme. Objects are often assumed to have to be of tremendous densities to become black holes. This is true for lower mass, smaller black holes, but calculating the required densities of larger mass black holes shows that this is not always the case. In fact, supermassive black holes, like those at the center of galaxies, can have a very low density.
Measuring g with a joystick pendulum
Authors: Bensky T. J.
Published: April 2003

A method for experimentally measuring g, the Earth’s gravitational acceleration, is presented. This method uses a computer joystick and computer as the primary measuring device. If a computer is available, it costs almost nothing to implement, and can be adapted for use as a high school or undergraduate lab exercise, or as a lecture demonstration.
Where is the sky?
Authors: Cohen Ariel , Galili Igal
Published: April 2003

This paper discusses the origin of the concept of sky. It is shown to emerge from one’s experience of the visual perception of nonluminous objects observed in/through the atmosphere during the daytime. The physical concept of visibility in the atmospheric environment underpins the perception of a flattened sky dome constructed by our mind. In addition, the Moon illusion receives a plausible explanation and both topics become appropriate for a conceptually oriented introduction course in physics and/or astronomy.
A proposition well known to geometers
Authors: Erlichson Herman
Published: April 2003

This note describes laboratory experiment ♯13 in the liberal arts physics course Galileo to Newton and Beyond. The title of these experiment is Newton’s Collision Experiments with Pendulums. Newton described these experiments in his Principia (pp. 22–25). He used these experiments to provide experimental confirmation for his action-reaction law. The note focuses on a mathematical proposition which was well known to geometers at the time of Newton, that “the velocity of a pendulum body in the lowest point is as the chord of the arc which it has described in its descent.”
Inexpensive coupled-oscillations demonstration
Authors: Sawicki Charles A.
Published: April 2003

Opposing magnetic dipoles attached to vertical brass strips were used to demonstrate coupled oscillations to large classes. As magnet separation was varied from 0.09 m to 0.28 m the time for energy exchange between the magnets increased from 2 s to 101 s.
Mystery motor demystified
Authors: Klittnick Arthur F. , Rickard Malcolm J.
Published: April 2003

We discuss a simple electric motor, which has been presented in science kits for children, but without explanation of its principles of operation. Since it lacks a commutator, its operation is mysterious. We describe easy to construct instrumentation to measure rotation angle and current in the motor, which leads to an understanding of its operation.
Let’s introduce more “mental math”
Authors: Sherfinski John
Published: April 2003

This paper argues for problems where the math can be done in one’s head (with g = 10 m/s2) so that physics concepts can be stressed and calculator use de-emphasized. Examples of standard problems are presented.
Using the internet for a collaborative study of the Moon’s phases
Authors: Oberem Graham E.
Published: April 2003

When students collect and share observational data of the phases of the Moon, the process of compiling a master calendar of the observations is time consuming and prone to transcription errors. We are addressing this issue by enabling students to enter their data via the Internet. Not only does this automate the compilation of a master calendar, but it also makes it relatively easy for classes widely separated geographically to collaborate in a study of the Moon’s phases.
Hear and “See” sound interference
Authors: Krider Jim , Cook Tim , Easterling Wayne , Rzanek Iwonna
Published: April 2003

To help students visualize the behavior of waves in sound interference phenomena, two transparent acetate wave trains representing the speaker output signals are used to show the phase relationship between them. The acetate wave trains slide past one another to show the changing phase relationship.
Pulling the rug from under round objects
Authors: Ferguson Joe L.
Published: April 2003

A lecture demonstration that involves pulling a rug from under a hoop and a disk has the hoop move faster and farther than the disk in a way that is easily understood on the basis of simple rotational dynamics.
An open-ended problem from history
Authors: Bartlett Albert A.
Published: April 2003

Two quotations from a history of battles present quantitative data about Welsh longbowmen in 14th-century warfare. The first datum is difficult to believe. The reader is asked to use first-year general physics to examine the reasonableness of these data and to set reasonable limits on the performance of the Welsh longbowmen.
A modification of Young’s Harmonic Sliders
Authors: Greenslade Thomas B.
Published: April 2003

My wife recently pointed out to me that the Young’s Harmonic Sliders device described in a previous note could be made with a lot less trouble by using a sliding template used by carpenters.
Motorized molecules: From molecular chaos to thermal order
Authors: Prentis Jeffrey J. , Yuhasz William M.
Published: April 2003

The sequence of random impulses due to“molecules” (squiggle balls) beating against a piston is measured using a force sensor. The equation of state (pV diagram) of the gas is obtained purely from a mechanical measurement (force sensor) and a statistical operation (time average).
Size of the Sun
Authors: Wootton Allen
Published: April 2003

Phtographs of the Sun taken in January and July allow comparison of the apparent size of the Sun as it appears in the Northern Hemisphere winter to its apparent size in the summer. This comparison allows teachers and students to address misconceptions about the reason for the seasons, to move to an understanding of the correct explanation, and to see direct evidence for the elliptical planetary orbits described in Kepler’s first law.
String of pearls resonance
Authors: Dindorf Wojciech
Published: April 2003

A favorite trick of mine involves using coral strings. This could be performed with necklaces, chains, or any sort of chain-like strings. Practice is required but almost everybody can learn it in a few minutes.
A note on integration of scalar products
Authors: Bauman Robert P.
Published: April 2003

A definite integral of a scalar product of vectors requires consideration of the angle between vectors in the original integral and may also involve an angle between vectors in a scalar product in the answer. In addition, there is often a change in variables in which the answer is expressed. This offers a third opportunity for change of sign, as illustrated by a common example.
Marloye’s harp and the thumb piano
Authors: Greenslade Thomas B.
Published: April 2003

This note has two sources: a 19th-century textbook illustration and the thumb pianos sold to tourists during my time at the University of West Indies in Jamaica in 1972-73. Both of these instruments produce sounds: one by setting bars into longitudinal vibrations, and the other using transverse vibrations. This note will show how the lengths of the bars to produce the same note are very different in the two cases.
“You don’t know what you think until you’ve heard what you said”
Authors: Blanton Patricia
Published: April 2003

As a new teacher, you face the daunting task of helping students “learn” physics. You think you know the material, you’ve read all the curriculum standards required for your state, and you’ve designed your lesson to convey the content objectives to your students.
Self-playing musical instrument
Authors: Bouffard Karen
Published: April 2003

This do-ahead Physics Olympics competition is a musical challenge based on one designed by Dan Calder for a past New Hampshire Physics Olympics. The objective is to build a musical instrument that is self-playing.
Welcome back
Authors: Mamola Karl
Published: April 2003

OK, here we go again. The start of another year with a new group of students filing into our classrooms and labs. I don’t know how many of you have noticed, but it’s been apparent to me that students’ attitudes have been changing somewhat, mostly for the better, over the past few years. I’m told that it’s due, at least in part, to the transition we’re experiencing from “Generation X” to the “Millenial generation.”
Nontraditional problems
Authors: Merhar Vida Kariž
Published: April 2003

As a teacher of physics at a secondary school, where we educate students between the ages of 14 and 18, I believe that students should be able to apply the principles of physics theoretically and practically when they begin their university education. This means that they should know basic physical laws and their range of validity.
Visualizing the thin-lens formula
Authors: Chakravarti Soumya , Siegel P. B.
Published: April 2003

Graphing 1/o versus 1/i is a valuable exercise for students to verify the thin lens equation. If two lenses are used in combination, the lens combination formula can also be verified by examining the intercepts.
Illuminating physics via web-based self-study
Authors: Greene Ronald L.
Published: April 2003

Gaining conceptual understanding of physics is difficult for many students. Interactive engagement classroom techniques have been shown to help alleviate this problem. This paper describes progress in addressing the problem from a different direction — that of students’ out-of-class study. Results from investigations employing several commonly used assessment instruments indicate that out-of-class study time can indeed be utilized to improve student learning of basic physics concepts.
Simulate interference...while supplies last
Authors: Chandler David
Published: April 2003

All students should see interference patterns for themselves. This note shows how interference patterns can be simulated using the pin feed strips from computer paper.
Getting families involved with physics
Authors: Barrett Mary Beth , Chiaverina Chris
Published: April 2003

Most physics teachers would agree that attempting to have students understand science without direct contact with the phenomena is like trying to teach them to swim without allowing them near the water. This note tells how to use the home environment to interest students in physics.
Who's taking ASTRO 101?
Authors: Deming Grace , Hufnagel Beth
Published: April 2003

Results from a sample of 3800 students taking the Astronomy Diagnostic Test Version 2.0 during 2001 have been used to create a profile of nonscience majors taking introductory astronomy at undergraduate institutions across the United States.
There is more to see than eyes can detect
Authors: Vollmer Michael , Möllmann Klaus-Peter , Pinno Frank , Karstädt Detlef
Published: April 2003

This paper briefly describes the method of infrared imaging and gives a selection of its numerous possible applications. Emphasis will be on the visualization of phenomena discussed in high school physics or introductory physics courses at college/university.
Improving the data analysis for falling coffee filters
Authors: Young Richard A.
Published: April 2003

This note involves the popular experiment of dropping coffee filters or balloons to provide students an opportunity to determine the velocity dependence of the air-resistance force.
Why do fields cancel inside a long cylindrical shell?
Authors: Lan Boon Leong
Published: April 2003

This note explains the cancellations that result in a zero net magnetostatic field inside an infinitely long, thin cylindrical shell carrying a uniformly distributed current. The explanation is easily adapted for the zero net electrostatic or gravitational field inside such a shell with a uniform distribution of charge or mass respectively.
Using the binomial theorem in introductory level physics
Authors: Blickensderfer Roger
Published: April 2003

The binomial expansion of (1 + x)n has a wide range of applicability in the solution of important physics problems at the introductory level. A few examples are given including the speed of sound in air and satellite orbital speeds.
“Stellar” interferometry with streetlights
Authors: Sharpe John
Published: April 2003

A simple experiment in optical interferometry is described that utilizes a small telescope or binoculars and streetlights as the sources. The experiment can be used to estimate the size of distant streetlights and to explain the principle of the Michelson stellar interferometer.
A variation on temperature conversion
Authors: Wenning Carl J.
Published: April 2003

An alternative, and possibly more memorable, way of converting between Fahrenheit and Celsius temperatures exists. It is based not upon the boiling point of water, but upon the fact that both scales read the same temperature at −40°.
A supersensitive LED Faraday's law demonstration
Authors: Ferguson Joe L.
Published: April 2003

A compact high-gain amplifier allows LEDs to reveal the direction induced current in a coil through which there is changing magnetic field.
Thermal properties of soil
Authors: McIntosh Gordon , Sharratt Brenton S.
Published: April 2003

Various thermal properties of soils accessible through fairly simple measurements are described. These properties include the insulating effect of soil, the existence of the soil temperature wave, and the propagation of this wave through the soil.
Models of traveling waves
Authors: Greenslade Thomas B.
Published: April 2003

When discussing transverse traveling waves with introductory students, I often feel hard pressed to get across the idea that the disturbance, y, is a function of both position x and time t.
Dynamics of a medieval missile launcher: the trebuchet
Authors: O'Connell James
Published: April 2003

In the Middle Ages, the heavy throw-weight launcher of choice was the trebuchet. When the heavy mass, attached to the short end of the pivoted beam, is released and falls, the projectile, which is in a sling fastened to the other end of the beam, begins to acquire a high velocity.
Color mixing with lasers
Authors: Russell Larry
Published: April 2003

When I teach optics to high school classes, I like to do the demo where I place red, green, and blue filters on white lights and then has the light overlap to create the complimentary colors.
Spacecraft artifacts as physics teaching resources
Authors: Robinett R. W.
Published: April 2003

This note examines the process that went in to making the engraved plaque carried on Pioneer 10 and 11 in order to specify our position in the galaxy and to show something of our nature.
The Bronx cheer effect
Authors: Gardner Martin
Published: April 2003

Have you ever been so annoyed by a TV commercial that you blew a raspberry at the set? Well, try this.
Physics of the seesaw
Authors: Pecori Barbara , Torzo Giacomo
Published: April 2003

The idea behind this article was inspired by a previously publishedTPT note on harmonic and anharmonic oscillators, in which the oscillations of a bar on a cube were briefly discussed. We thought these oscillations deserved quantitative experimental investigation and that automated data acquisition could allow the data to be gathered.
Impact of national standards on research equipment in the classroom
Authors: Bailey Janelle M. , Slater Timothy F.
Published: April 2003

In the project evaluation for the Princeton Earth Physics Project (which funded the distribution of research-grade scientific equipment to the classroom), teacher-participants stated that the impact of national and state science education standards has had a positive influence on the use of seismometers in their classrooms.
The use of radar-gun technology in the physics classroom/laboratory
Authors: Baker Blane
Published: April 2003

The ability to measure speeds of objects without the need for timers, photogates, or specialized experimental setups is extremely helpful in teaching/learning physics. Such measurements are made possible using current-generation radar guns. In our efforts to provide learning experiences that incorporate familiar technology, we have introduced radar guns into an introductory physics classroom and a general-education laboratory.
Analyzing simple circuits
Authors: Vreeland Pete
Published: April 2003

This article describes a method for solving series and parallel circuit problems that uses a graphic organizer to show the relationship between electric current, voltage, and resistance in series and parallel circuits.
PER-based reform at a multicultural institution
Authors: Steinberg Richard N. , Donnelly Kofi
Published: April 2003

Physics education research (PER) has taught us much about how our students learn (or fail to learn) physics. In this article we give a brief overview of PER and describe the implementation of highly interactive PER-based instructional strategies at City College of New York, a very diverse inner-city school.
Stable equilibrium at the top of a hill
Authors: Dindorf Wojciech
Published: April 2003

Here is an interesting phenomenon that can be investigated at home. The experiment is highly reproducible and a bit puzzling. So far as I know, there is no direct explanation in any textbook.
The most important lesson
Authors: Rhodes Charles
Published: April 2003

I consider three questions when planning to teach: “What am I going to have my students do today? What’s it good for? How do I know?” Serious consideration of these three simple questions has great power to transform the community of learners in any classroom.
A spooky rotation
Authors: Gardner Martin
Published: April 2003

A new and amazing optical illusion has come to light.
Tension in a pendulum string
Authors: O’Connell James
Published: April 2003

Tension in the string of a simple swinging pendulum is measured and compared with a theoretical expression. Good agreement is found with a simple sine wave with half the pendulum’s period.
The speed of sound in an iron rod
Authors: Potter David
Published: April 2003

The speed of sound in a solid has traditionally been measured by inducing resonance in a long rod, sometimes by magnetostriction, sometimes by electrostatic attraction, more often by a mechanical driver.
Obtaining Wien's displacement law from Planck's law of radiation
Authors: Das Biman
Published: April 2003

Wien’s displacement law states that the wavelength at which the radiated power is a maximum for a blackbody varies inversely with the temperature. This relationship is important in astrophysics for determining the temperature of stars. The objective of this note is to show that in teaching introductory (calculus-based) or intermediate physics, instead of simply stating Wien’s displacement law, instructors can ask students to derive if from Planck’s radiation law. A numerical solution to a transcendental equation is required, easily accomplished using a symbolic math program such as Maple or Mathematica.
How does the potential energy of a rising helium-filled balloon change?
Authors: Keeports David
Published: April 2003

I discuss why the buoyant force as given by Archimedes’ principle is a conservative force with an associated potential energy. I then provide several arguments why a rising helium balloon loses potential energy.
As simple as possible
Authors: Herman Rhett
Published: April 2003

An extremely simple method for building a basic loudspeaker is presented. This loudspeaker may be built in just a few minutes from a bare minimum of materials.
The floating vase
Authors: Gardner Martin
Published: April 2003

This remarkable optical illusion illustrates how our minds make the best bet in interpreting a picture in the light of experience.
Downhill Races
Authors: Melvin Cruse
Published: April 2003

Discussions of downhill races have been evolving in introductory texts. This article presents a logical sequence to guide students through the essential factors in this multifaceted topic. Comparative examples and a technical supplement are provided to reinforce the logic. Slipping, surface compressions, bounces, wobble, and internal material shifts are considered adverse effects.
MBL Experiment in Angular Momentum
Authors: Gluck Paul
Published: April 2003

Among the series of beautiful take-home experiments designed by A.P. French and J.G. King for MIT students, the one on angular momentum studies the loss and conservation of angular momentum using a small dc motor as generator. Here we describe a version of the experiment that increases its accuracy, enables students to perform detailed rotational dynamics calculations, and sharpens the ability to isolate the region where the collision occurs.
What and how to teach?
Authors: Mamola Karl C.
Published: April 2003

At first I was a bit skeptical about devoting two whole pages to the opinion pieces by Pasachoff and Caton in our September issue. But judging from the number of thoughtful and spirited responses we’ve received, it was space well used.
Small inexpensive diamagnetic levitation apparatus
Authors: Sawicki Charles A.
Published: April 2003

A small, inexpensive (5 x 5 x 9 cm and $17) diamagnetic levitation apparatus is described in which a cubic NdFeB magnet 0.476 cm on a side is suspended in a potential energy well created using small ceramic disk magnets and two graphite plates.
Role of Experiments in Physics Instruction — A Process Approach
Authors: Etkina E. , Van Heuvelen A. , Brookes D. T. , Mills D.
Published: April 2003

This paper describes an approach to classroom experiments that serves roles closer to that in the practice of physics. We propose that in the history of physics most “classical” experiments fall into one of three groups: observational experiments, testing theoretical model experiments, or application experiments.
An Archimedes’ Principle Activity
Authors: Fakhruddin Hasan
Published: April 2003

This experiment describes a small beaker containing a block of wood floating in water. When you take the wood out of the small beaker and let it float in the water, the water level stays the same.
Mathematical Reasoning Over Arithmetic in Introductory Astronomy
Authors: Slater Tim , Adams Jeff
Published: April 2003

Paper presents a rationale and strategies for including quantitative reasoning in introductory astronomy courses for nonscience majors without focusing on computations.
Static Elongation of a Suspended Slinky™
Authors: Sawicki Mikolaj “Mik”
Published: April 2003

Elongation of a vertically suspended Slinky under its own weight and a weight hung from it is discussed using elementary considerations. Displacement of the center of mass of Slinky is also found. The results are verified experimentally using a $1 apparatus.
The Magnetic Field Along the Axis of a Long Finite Solenoid
Authors: Chia Chih-Ta , Wang Ya-Fan
Published: April 2003

A multimeter is used to measure the magnetic field along the central axis of a long finite solenoid. Experimental results are consistent with the theoretical calculation presents in general physics textbooks.
A Boatload of Pennies
Authors: Weston Ralph E.
Published: April 2003

A favorite event in Science Olympics, often held in elementary and secondary schools, is the construction of an aluminum-foil boat, the seaworthiness of which is then tested by observing how much weight (pennies or washers) it will hold before sinking. The pedagogical value of the contest is to lead the students into a discussion of such things as density and Archimedes? principle. Here is a simple calculation to determine the optimum shape of the boat.
Wien’s Law and the Temperature of the Sun
Authors: Biermann Mark L. , Katz Debora M. , Aho Robert , Diaz-Barriga James , Petron Jerome
Published: April 2003

A simple approach is used in an attempt to determine the temperature of the sun by modeling the sun as a blackbody radiator and applying Wein's Law. Apparently excellent results are obtained, but the results are false as a consequence of two corrections which cancel out.
Beats in an Oscillator Near Resonance
Authors: Gaffney Chris A. , Kagan David
Published: April 2003

When a hanging mass-spring system is driven with an audio speaker near its natural frequency, one observes very long lived beats. Besides being a beautiful example of beats in a mechanical system, their presence is in fact initially surprising. Combining a simple analysis with measurements from a PASCO motion sensor, a satisfactory understanding emerges.
Introducing Specific Heat Through Cooling Curves
Authors: Mattos C. R. , Gaspar A.
Published: April 2003

We propose a simple way to introduce the concept of specific heat through the use of cooling curves. Good qualitative results for the specific heat of aluminum are achieved. This approach allows one to introduce a discussion of the actual heat exchange processes and provides opportunities for discussing factors that contribute to error.
Start Using “Hollywood Physics” in Your Classroom!
Authors: Dennis Chandler M.
Published: April 2003

A dynamic way to tap into the visual learning capability in all physics students using big screen movies is described.
Hands-On Earth Rotation
Authors: Euler Manfred , Braune Gert
Published: April 2003

A Foucault pendulum equipped with a low-cost computer interface is described. It allows one to measure the precession rate of the plane of oscillation due to Earth rotation within a few minutes. A graphic interface (PC tablet) serves as a frictionless two-dimensional position sensor. By using standard software tools it is possible to record the position of the pendulum up to 50 samples/s. Although the sensor provides only rather coarse-grained data, the method is remarkably precise due to statistical analysis of the data.
Help at Your Fingertips
Authors: Blanton Patricia
Published: April 2003

Studies have shown that many physics teachers experience feelings of isolation because they are often the only physics teacher in the school. Perhaps you are looking for someone to share your ideas about teaching a particular topic. You need suggestions about how to help students learn a specific concept. Maybe you are looking for instructions about performing a demonstration or experiment, or need some guidance in choosing an approach to a particular concept. You might even have tried an approach that failed miserably and you are looking for guidance from someone with experience. Where do you turn?
An Old Pilot’s Yarn
Authors: Kagan David
Published: April 2003

Pilots have an old yarn that states the air speed of a plane can be found by measuring the ground speed of the plane when the air speed is directed along each cardinal (north, south, east, and west) and averaging the four values. Understanding the mechanism behind this proposition requires the application of some basic vector properties and might be a useful exercise for your students.
Deep Impact: The Physics of Asteroid/Earth Collisions
Authors: Metz Donald , Stinner Arthur
Published: April 2003

About 65 million years ago, a great change took place: more than half of the world's reptiles vanished along with more than half of all species of plants, and land and marine animals, including the dinosaurs. Mammals somehow survived and became the dominant large animal. One of these species lived long enough eventually to investigate the fossil record of its distant origins and ask the question: Who or what committed the mass murder?
Easy Ways to Add Interest to Your Physics Classroom
Authors: DePino Andrew
Published: April 2003

Here are ways of brightening up or adding interest to my classroom and would like to share a few of my successes with other teachers.
Meet your new president: Thomas O'Kuma
Authors: Clark Robert Beck
Published: April 2003

Robert Beck Clark introduces the 1998 AAPT President, Thomas O’Kuma of Lee College.
Two stunts with eggs
Authors: Gardner Martin
Published: April 2003

Try these two physics tricks with an egg.
Reverse jack’s profile
Authors: Gardner Martin
Published: April 2003

This physics trick involves the “one-eyed” jacks in a deck of cards and a glass of water.
Match penetration
Authors: Gardner Martin
Published: April 2003

This physics trick uses a match and a safety pin to create a similar illusion to that created by an owl rotating its head.
Physics textbook illustrations
Authors: Greenslade Thomas B.
Published: April 2003

The phrases “works of art” and “physics textbooks” rarely occur in the same sentence. But a 1943 University of Chicago physics textbook, Analytical Experimental Physics by Lemon and Ference, has chapter headings that could easily be framed and placed in an art gallery. Eight of them are reproduced here
Two rollers and a yardstick
Authors: Gardner Martin
Published: April 2003

A physics trick involving two paper-towel tubes and a yardstick is described.
A pebble curiosity
Authors: Gardner Martin
Published: April 2003

For this experiment you need a supply of marbles of two different sizes. Any kind of small spheres will do also, such as spherical bubble gum and candy. Assuming you are using marbles, fill a glass to the brim with the small marbles, and fill another glass to the brim with the larger marbles. Which glass has the larger volume of empty space?
Introductions and aspirations
Authors: Mamola Karl
Published: April 2003

In his first editorial, Karl Mamola introduces the new editorial team and elaborates his hopes and goals for the future of The Physics Teacher.
Why K, L, M. . .?
Authors: Hayn Carl H.
Published: April 2003

The innermost atomic shells received the designations K, L, M in a circuitious way. Barkla had assigned these letters to the x-ray series that he observed. Later Kossel introduced these same names to the atomic levels at which the various x-ray transitions terminated.
The water knot
Authors: Gardner Martin
Published: April 2003

This physics trick uses a plastic bottle with three holes punched near the bottom. When the bottle is filled with water, three streams emerge from the holes.
Phase Changes in Reflected Sound Waves
Authors: Potter David
Published: April 2003

Phase changes in waves are just varied enough and just unfamiliar enough to students to be confusing. The phase changes upon reflection of waves on a string and of sound waves are usually the first to be encountered by students, and can give a bridge to other such changes found, for example, in electromagnetic waves. Before digital oscilloscopes, phase changes in sound waves had to be taken on faith or tested indirectly. Now they are quite easy to show. This note describes an experiment that demonstrates phase changes of a reflected sound pulse in a long air-filled tube. The demonstration also gives an easy and straightforward measurement of the speed of sound, and shows that air temperature matters while pressure does not, as theory predicts.1
Spreadsheet-Based Exercises for Introductory Laboratories
Authors: Elliott Annie B. , Murray Stephen D. , Ward Richard A.
Published: April 2003

The astronomy curriculum at Las Positas College is a familiar one to many readers — a lecture course on the solar system, another on stars and galaxies, and a separate laboratory course. The laboratory therefore has students who have never heard of some topics, and others who have just had lectures on them. Also, many topics cannot be brought into the laboratory, leading us to rely heavily upon computer-based exercises. Two of these are Kepler's laws of planetary motion and stellar structure. In developing these exercises, we have explored the use of the Microsoft® Excel spreadsheet program. Excel has the advantage of being easier to learn and implement than Java, while also being able to do sophisticated computations.1, 2 At the same time, it may be used to present material in a visually appealing manner, resembling the layout of webpages.
Assessment Strategies for Laboratory Reports
Authors: Nadji Taoufik , Lach Michael , Blanton Patricia
Published: April 2003

National and state science standards tell us that we should use inquiry approaches to help students develop understanding of key concepts. Physics education research groups have validated the effectiveness of this approach. It is then left to the teacher to provide the scaffolding on which to construct these concepts, the guidance necessary to complete the task, and the assessment strategies to evaluate the effectiveness of the approach. Most teachers will require students to write a report to communicate their efforts and understanding, and then are faced with the enormous task of grading the volumes generated in an efficient, consistent, and fair manner. Two teachers share with us some of the strategies they use.
Sundogs, Ice Crystals, and Bernoulli
Authors: Edge Ron
Published: April 2003

The mechanism is presented whereby “sun dogs” are formed. These are the bright colored spots appearing on either side of the Sun in the presence of atmospheric ice crystals.
Optimization Analysis of Projectile Motion Using Spreadsheets
Authors: Godsen Scott
Published: April 2003

This note explores the situation of a projectile being launched from a height h above ground level and determining the optimal angle of launch such that it will reach a maximum horizontal displacement. Using a spreadsheet such as Microsoft Excel®, the optimum angle for given values of height and initial velocity v can be readily determined.
Foot Beats
Authors: Greenslade Thomas B.
Published: April 2003

Recently, when walking along one of the few sidewalks in Gambier, I noticed that the toe of my right foot came down on one of the uniformly spaced dividers in the concrete pavement every twelve double strides. Further, I noticed that my stride seemed to be about five inches longer than the distance between cracks. The distance between cracks was 60 in, based on the fact that a dollar bill is about 1/8 in longer than six inches.
Enhancing the Student-Instructor Interaction Frequency
Authors: Bullock D. W. , LaBella V. P. , Clingan T. , Ding Z. , Stewart G. , Thibado P. M.
Published: April 2003

A 100-fold increase in the frequency of student–teacher interaction has been achieved in a large-enrollment classroom. Students answer in-class questions using personalized hand-held transmitters. Outside the classroom, personalized homework sets are generated and collected via the Internet.
A Bright Color Mixer
Authors: Cockman John
Published: April 2003

A perfect trichromatic light mixer can be constructed from an old or obsolete three-panel LCD projector. These projectors use dichroic mirrors to split the light into red, green, and blue beams. The beams are directed through three polysilicon LCDs, recombined by mirrors or a cube-prism, and superimposed on the screen to produce a full-color image.
More Diamagnetism Demonstrations
Authors: Conery Chris , Goodrich L. F. , Stauffer T. C.
Published: April 2003

Inspired by, among others, Charles Sawicki's description of an inexpensive diamagnetic levitation apparatus,1 we built two such devices for classroom use and for educational outreach at the National Institute of Standards and Technology, Boulder, Colo. With a slightly different setup, the same demonstration can be done horizontally on an overhead projector.
A Background to Background Radiation
Authors: Deacon Christopher G.
Published: April 2003

The study of radiation at the introductory college level usually includes experiments to determine the half-life of a radioactive isotope and also a study of the absorption of nuclear radiation by metal foils. These experiments are straightforward to do using a Geiger-Müller tube and scaler, and allow for the determination of well-known constants. The underlying theory behind these experiments is also easy to understand, but fails to take into account background radiation that will be present, regardless of the source being used. The purpose of this article is to show how students can measure the effect of background radiation on these experiments by modifying the standard textbook theory.
Enhancing Student Learning by Tapping into Physics They Already Know
Authors: Vondracek Mark
Published: April 2003

This paper describes a teaching strategy in physics classes that encourages teachers at all levels to develop assignments and assessments that tap into events and situations that students experience everyday. The key to the strategy is to allow students to choose the situation and then develop their own explanation for what happens and why it happens using specific physics principles discussed in class. After doing assignments based on this strategy, students report better long-term understanding, increased confidence, more enjoyment from the class, and an increased sense that knowing some physics is worthwhile.
How Is Your Gas Mileage?
Authors: Summers Richard
Published: April 2003

Most students do not get an appreciation of what their gasoline dollar buys them even after they have taken lessons on heat and thermodynamics. The common conception is that most of the fuel put in the fuel tank is used for running the engine and that the only reason for energy waste is poor engine maintenance. I decided to help students gain a better idea of how thermodynamics really relates to their lives by having them do a rough experimental analysis of the efficiency of their engines.
Compact Disk Spectroscopes Revisited!
Authors: Byrne Aidan
Published: April 2003

The recent article by Tim Knauer1 indicates again that the CD provides a wonderful learning resource for physics teachers and students. There is much to be learned by examining the nature of the way information is stored and retrieved on the disk as well as the physical medium itself. Books such as Muller's Upgrading and Repairing PC's2 provide a useful compendium of the properties of the medium as well as the methods of encoding.
Acceleration Without Force?
Authors: Johns Robert
Published: April 2003

Nonsense! No mass can change its state of motion unless a force acts on it. But acceleration without any force is just what introductory textbook authors are implying when their only explanation of changes in rotational motion is the conservation of angular momentum with no mention of any force. Conservation laws connect the initial and final states of a system, correctly predicting the final state, but they do not reveal how the change is made or what forces are acting to produce that change. This paper discusses two applications found in introductory texts and includes some dynamics that clarify the motions.
On Morphing Neutrinos and Why They Must Have Mass
Authors: Hecht Eugene
Published: April 2003

This paper explores the recently confirmed hypothesis that neutrinos have mass and that they spontaneously transform from one type to another. That immensely important discovery culminates 40 years of experimental research. After briefly discussing that work, we'll study the quantum mechanical explanation of these phenomena elaborating the concepts of particle mixing, and the oscillation of flavor types. These rather esoteric ideas lead to the prediction that morphing neutrinos must have mass, but there's a much more elegant relativistic argument that brings us to this same conclusion.
Air Resistance on Falling Balls and Balloons
Authors: Gluck Paul
Published: April 2003

Studying the effect of air resistance on falling objects in an introductory mechanics course has the merit of relevance to a considerable part of our everyday experience: Leaves, parachutes, raindrops, or soot particles do not keep accelerating as they fall. This topic has been discussed in this and other journals many times,1–7 ranging from theoretical treatments to various experimental investigations, mostly for coffee filters, depending on the apparatus at the disposal of the writers (video clips, graphic calculators, and so on). We report here a sequence of activities for our 11th-grade high school students dealing with this topic. The analysis of data emphasizes points that do not seem to have been done in previous articles.
Applying Physics to the Student's World
Authors: Blanton Patricia
Published: April 2003

It has been a challenging day. The electricity is off because snow and extreme winds have toppled trees into power lines all across my county. As I've been trying to devise a way to cook dinner, I've been thinking about how equipped we are to handle such emergencies. My husband, who has worked most of the day getting the portable generator going and figuring out how to hook up things to keep us warm and safe, made the comment, “You have to be a MacGyver if you are going to be a homeowner.“ I began wondering how well we are equipping our students with the ability to figure out how to make things work. We teach the physics principles so they can solve the “book problems,“ but are we helping them to understand the principles well enough to become real problem solvers? Are they prepared to handle situations when the “usual things“ aren't working?
Action@Distance: Using web and take-home labs
Authors: Abbott Hilton
Published: April 2003

Technical Physics is taught using the Web, student-built equipment, and computer-generated problem sets. The Hands-On-Physics project, by the Concord Consortium, provides primary content for the course.
A space-age portrait of the active sun
Authors: McKenzie David E. , Slater Timothy F.
Published: April 2003

Recent observations from space observatories focused on high energy emission from the Sun has provided both exciting science and beautiful pictures, particularly in X-ray wavelengths. This manuscript is adapted from an invited Frontiers in Astronomy talk given at the AAPT Winter Meeting, New Orleans, January 1998 on current research in solar physics.
Torque rack demonstrator
Authors: Tomac Mike
Published: April 2003

Brain-teasing torque demos are a part of every physics teacher’s repertoire. I can thank Ted Foster of Cal Poly, San Luis Obispo, for my personal favorite, the “torque rack.”
The time delay in human vision
Authors: Wardle D. A.
Published: April 2003

Nijhawan has published an intriguing demonstration that indicates that humans are partially able to correct for the time delays inherent in their vision. Nijhawan’s demonstration is briefly discussed and a simple apparatus for reproducing the demonstration is described.
Vectortine’s Day
Authors: Lock Frank
Published: April 2003

Holidays at Lemon Bay High are days of unusual activities, as they well may be at other high schools. One of our special days is Valentine’s Day. In order to maintain some academic focus in the physics department, while allowing my students to participate in the celebration, we’ve developed a physics version of the hearts-and-flowers February celebration. It’s Vectortine’s Day in physics class.
The disappearing student
Authors: DePino Andrew
Published: April 2003

This demonstration is based on the familiar blind-spot phenomenon, except on a larger scale. I announce to the class that I will make one of them disappear and reappear right before their very eyes!
Build your own soliton generator
Authors: Nassar Antônio B.
Published: April 2003

This work provides a step-by-step guideline for the construction of a simple, low-cost generator of a nonpropagating hydrodynamic soliton.
PSSC’s Science Study Series
Authors: Whitaker Robert J.
Published: April 2003

Early in 1957, a report was published describing the formation of the “Physical Science Study Committee” (PSSC) the previous December and its proposed December and its proposed new physics program for secondary schools.
The variable gravity pendulum
Authors: Feliciano José
Published: April 2003

Traditionally, the period of the pendulum has been studied experimentally by suspending a bob on a thin, light string, displacing the bob until the string makes an angle Θ with the vertical, and then releasing the bob.
Finding needles in haystacks
Authors: Livingston James D.
Published: April 2003

There are many different approaches to teaching K-12 science. With so many possibilities, picking the best approach is like trying to find a needle in a haystack — very difficult, unless you use magnets.
Estimating the size of blood cells by staring into space
Authors: Keeports David
Published: April 2003

An order-of-magnitude estimate of the size of red blood cells is obtained by locating a distant object whose height in the visual field matches that of an eye floater and then calculating the retinal image height of that object.
Simple sound demonstrations
Authors: Huebner Jay S. , Sundaralingam N.
Published: April 2003

Simple, yet robust and reliable demonstrations to show that the velocity of sound in gases varies with temperature and inversely with the molecular weight of the gas are described.
A thought-provoking demonstration
Authors: Cowley E. Roger , Holton Brian , Horton George K.
Published: April 2003

We present and discuss a physics demonstration, similar to, but distinct from, the ballistic-pendulum demonstration, one that illustrates all three conservation laws of mechanics (for energy, momentum, and angular momentum) simultaneously.
Accuracy of global positioning system receivers
Authors: Biermann Lois A. A. , Daws Rebecca J. , Schumacher Helen A. , Biermann Mark L.
Published: April 2003

The use of the Global Positioning System is becoming increasingly widespread. We present the results of a study in which simple experimental techniques and statistical analysis were used to measure the accuracy of a Global Positioning System device.
A closer look at the spectrum of helium
Authors: Lo Presto Michael C.
Published: April 2003

When observing the spectrum of helium in an introductory physics laboratory, a complete and satisfactory laboratory experience that provides insight into the connection between the observed wavelengths and the structure of the atom, is more difficult to achieve than when observing hydrogen. The reason for this is that a complete diagram of the observed helium spectrum and the accepted wavelengths are much harder to find in readily available references than they are for hydrogen. Using a reference that does provide this information, I have developed what I believe is a more complete and informative experiment on the spectrum of helium that other !!physics instructors may find useful.
Astrophysical perspective in teaching special relativity
Authors: Blackman Eric G.
Published: April 2003

The importance of teaching a clear definition of the “observer” in special relativity is highlighted using a simple astrophysical example from an exciting subject area of current research. Astrophysical applications of special relativity complement idealized examples with real applications and very effectively exemplify the role of a finite light travel time.
Right-hand rule with magnet and monochrome monitor
Authors: Saba Marcelo M. F.
Published: April 2003

A simple and inexpensive study of the interaction between electrons and the magnetic field can be done with an old computer (or oscilloscope) with black and white screen and a small bar magnet.
Standing waves on a hanging rope
Authors: Gibbs Robert E.
Published: April 2003

A simple model is presented for waves traveling on a vertical rope of uniform density. The waves travel with an upward acceleration of g2. The standing wave frequencies and nodal positions for the modes of oscillation are calculated. The standing wave frequencies form a series of odd harmonics. The results are compared to those derived by Satterly.
Getting the feel for vector addition of forces
Authors: Bracikowski Christopher , Garcia P. Joseph , Harper David J.
Published: April 2003

Authors describe an experiment in which students actively participate in the vector addition of forces by using spring scales.
Measuring the forces required for circular motion
Authors: Henderson Charles
Published: April 2003

An easy-to-construct apparatus can be used with an MBL force probe to allow students to measure the forces acting on a mass moving in horizontal or vertical circular motion. The apparatus and its construction are described and sample data is discussed.
Kepler’s third law: Equal volumes in equal times
Authors: Bucher Manfred
Published: April 2003

Using the average orbital speed, Kepler’s third law is geometrically visualized similar to the familiar graphical representation of Kepler’s second law.