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Mar 2013

Volume 51, Issue 3, pp. 132-191

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THE 3 Rs

Paul Hewitt

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 132

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01.50.-i Educational aids
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
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Dark Matter

Don Lincoln

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 134

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It's a dark, dark universe out there, and I don't mean because the night sky is black. After all, once you leave the shadow of the Earth and get out into space, you're surrounded by countless lights glittering everywhere you look. But for all of Sagan's billions and billions of stars and galaxies, it's a jaw-dropping fact that the ordinary kind of matter like that which makes up you and me is but 5% of the energy budget of the universe. The glittering spectacle of the heavens is a rather thin icing on a very large and dark cake.
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01.50.-i Educational aids
95.35.+d Dark matter (stellar, interstellar, galactic, and cosmological)
95.36.+x Dark energy
98.80.Jk Mathematical and relativistic aspects of cosmology
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Moments of Inertia of Disks and Spheres Without Integration

Seok-Cheol Hong and Seok-In Hong

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 139

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Calculation of moments of inertia is often challenging for introductory-level physics students due to the use of integration, especially in non-Cartesian coordinates. Methods that do not employ calculus have been described for finding the rotational inertia of thin rods and other simple bodies.1–3 In this paper we use the parallel axis theorem and the perpendicular axis theorem (both of which may be proved without calculus4), along with rotational symmetry, to determine, without using integration, the moments of inertia of uniform disks and spheres.
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01.50.-i Educational aids
46.70.-p Application of continuum mechanics to structures
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Bringing the Digital Camera to the Physics Lab

M. Rossi, L. M. Gratton, and S. Oss

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 141

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We discuss how compressed images created by modern digital cameras can lead to even severe problems in the quantitative analysis of experiments based on such images. Difficulties result from the nonlinear treatment of lighting intensity values stored in compressed files. To overcome such troubles, one has to adopt noncompressed, native formats, as we examine in this work.
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01.50.-i Educational aids
42.30.Va Image forming and processing
42.79.Pw Imaging detectors and sensors

Spherical Tippe Tops

Rod Cross

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 144

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A tippe top (see Fig. 1) is usually constructed as a truncated sphere with a cylindrical peg on top, as indicated in Fig. 2(a). When spun rapidly on a horizontal surface, a tippe top spins about a vertical axis while rotating slowly about a horizontal axis until the peg touches the surface. At that point, weight is transferred to the peg, the truncated sphere rises off the surface, and the top spins on the peg until it is upright. A feature of a tippe top is that its center of mass, labeled G in Fig. 2, is below the geometric center of the sphere, C, when the top is at rest. That is where it will return if the top is tilted sideways and released since that is the stable equilibrium position. The fact that a tippe top turns upside down when it spins is therefore astonishing. The behavior of a tippe top is quite unlike that of a regular top since the spin axis remains closely vertical the whole time. The center of mass of a regular top can also rise, but the spin axis tilts upward as the top rises and enters a “sleeping” position.
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01.50.-i Educational aids
45.20.D- Newtonian mechanics

Wiimote Experiments: Circular Motion

Minjoon Kouh, Danielle Holz, Alae Kawam, and Mary Lamont

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 146

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The advent of new sensor technologies can provide new ways of exploring fundamental physics. In this paper, we show how a Wiimote, which is a handheld remote controller for the Nintendo Wii video game system with an accelerometer, can be used to study the dynamics of circular motion with a very simple setup such as an old record player or a bicycle wheel.
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01.50.My Demonstration experiments and apparatus
45.40.-f Dynamics and kinematics of rigid bodies
01.50.H- Computers in education

Teaching Astronomy Using Tracker

Mario Belloni, Wolfgang Christian, and Douglas Brown

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 149

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A recent paper in this journal1 presented a set of innovative uses of video analysis for introductory physics using Tracker. In addition, numerous other papers have described how video analysis can be a meaningful part of introductory courses.2–4 Yet despite this, there are few resources for using video analysis in introductory astronomy classes. In this paper we describe the use of Tracker in introductory astronomy to analyze a “video” consisting of a series of still images of star fields and sunspots. Because astronomy focuses on concepts unfamiliar to most students, the visualization that video analysis provides can be especially valuable.
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01.50.F- Audio and visual aids
01.50.My Demonstration experiments and apparatus
96.60.qd Sun spots, solar cycles
97.00.00 Stars

Adding Albedo and Atmospheres

Michael C. LoPresto

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 152

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In a previous article in this journal,1 we reported on a laboratory activity in which students used a derivation from the Stefan-Boltzmann law to calculate planetary temperatures and compare them to measured values from various (mostly online) sources. The calculated temperatures matched observed values very well with the exceptions of Venus and the dwarf planet Pluto.
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01.50.-i Educational aids
92.60.hv Pressure, density, and temperature
96.12.Jt Atmospheres
96.30.Ea Venus
96.30.Sn Pluto

Moving Clocks Do Not Always Appear to Slow Down: Don't Neglect the Doppler Effect

Frank Wang

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 154

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In popular accounts of the time dilation effect in Einstein's special relativity, one often encounters the statement that moving clocks run slow. For instance, in the acclaimed PBS program “NOVA,”1 Professor Brian Greene says, “[I]f I walk toward that guy… he'll perceive my watch ticking slower.” Also in his earlier piece for The New York Times,2 he writes that “if from your perspective someone is moving, you will see time elapsing slower for him than it does for you. Everything he does … will appear in slow motion.” We need to be care- ful with this kind of description, because sometimes authors neglect to consider the finite time of signal exchange between the two individuals when they observe each other. This article points out that when two individuals approach each other, everything will actually appear in fast motion—a manifestation of the relativistic Doppler effect.3
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01.50.-i Educational aids
03.30.+p Special relativity
03.65.Pm Relativistic wave equations

An Arduino-Controlled Photogate

Calin Galeriu

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 156

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It is hard to imagine teaching physics without doing experimental measurements of position as a function of time. These measurements, needed for the determination of velocity and acceleration, are most easily performed with the help of photogates.1,2 Unfortunately, commercial photogates are rather expensive. Many require the purchase of an additional matching timer or other electronic device. Sometimes special software is also needed. The total bill can easily become prohibitive. For this reason physics teachers have shown considerable interest for cheaper, in-house designed and manufactured photogates.3–6 The photogate systems described in the literature have their limitations. Some rely on a digital stopwatch and therefore cannot measure time with a precision higher than 0.01 seconds. Some use photoresistors that have a slower response than phototransistors. Some are based on the computer microphone port and therefore cannot handle more than two photogates (two audio channels) at the same time. Extracting the time information from an audio file can also be a challenge for some students. We describe here a photogate system that matches the performance of a commercial one but at a fraction of the cost. The key to this success is the use of an Arduino microcontroller for data collection. The Arduino platform, initially developed for electronics and robotics educational projects, has recently been incorporated in physics labs.7 The Arduino microcontroller, because of its low cost and because it provides a broad exposure to electronics and computer programming, is an ideal tool for integrated STEM projects.
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01.50.Pa Laboratory experiments and apparatus
85.60.Dw Photodiodes; phototransistors; photoresistors
01.50.ht Instructional computer use

Beautiful Science: Worth a Visit

Frederick M. Bingham

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 159

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For those in the profession of teaching physics who reside in or plan to visit the Los Angeles area, I would highly recommend a trip to the Huntington Library in San Marino, specifically to a permanent exhibit entitled “Beautiful Science: Ideas that Changed the World” in the Dibner Hall of the History of Science. The exhibit contains original books and manuscripts from the library's own collections. The sheer magnitude of human achievement represented here and the amount of effort and money that must have been required to amass these books boggles the mind.
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01.50.fh Posters, cartoons, art, etc.
42.00.00 Optics
95.00.00 Fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations

The Orion Constellation as an Installation: An Innovative Three-Dimensional Teaching and Learning Environment

Daniel Brown

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 160

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Visualizing the three-dimensional distribution of stars within a constellation is highly challenging for both students and educators, but when carried out in an interactive collaborative way, it can create an ideal environment to explore common misconceptions about size and scale within astronomy. We present how the common tabletop activities based upon the Orion constellation miss out on this opportunity. Transforming them into a walkthrough Orion installation that includes the position of our solar system allows the students to fully immerse themselves within the model and experience parallax. It enables participants to explore within the installation many other aspects of astronomy relating to sky culture, stellar evolution, and stellar sizes, establishing an innovative learning and teaching environment.
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01.50.My Demonstration experiments and apparatus
95.10.Jk Astrometry and reference systems
97.21.+a Pre-main sequence objects, young stellar objects (YSO's) and protostars (T Tauri stars, Orion population, Herbig-Haro objects, Bok globules, bipolar outflows, cometary nebulae, etc.)

Mechanical Parametric Oscillations and Waves

William Dittrich, Leonid Minkin, and Alexander S. Shapovalov

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 163

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Usually parametric oscillations are not the topic of general physics courses. Probably it is because the mathematical theory of this phenomenon is relatively complicated, and until quite recently laboratory experiments for students were difficult to implement.1 However parametric oscillations are good illustrations of the laws of physics and can be explained qualitatively; by using PASCO equipment,2 quantitative laboratory experiments can be designed rather easily. Below the following experiments are described: parametric oscillations of a simple pendulum, a vertical spring-mass system, and a stretched string.
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01.50.My Demonstration experiments and apparatus
01.50.Pa Laboratory experiments and apparatus
07.10.-h Mechanical instruments and equipment

Hands-On Nuclear Physics

Jeff Whittaker

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 166

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Nuclear science is an important topic in terms of its application to power generation, medical diagnostics and treatment, and national defense. Unfortunately, the subatomic domain is far removed from daily experience, and few learning aids are available to teachers. What follows describes a low-tech, hands-on method to teach important concepts in nuclear physics, including the quark model, anti-matter, nuclear binding energy, stability, the nuclear shell model, and the importance of symmetry, by making use of neodymium disc magnets.
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01.50.-i Educational aids
14.20.Dh Protons and neutrons
20.00.00 NUCLEAR PHYSICS
01.40.gb Teaching methods and strategies

Teachers' self-assessed level of preparation

Susan White

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 168

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We asked high school physics teachers to assess their level of preparation across a number of domains. Almost all (98%) reported feeling adequately or well prepared in terms of their basic physics knowledge. The chart presents teachers' responses to their self-assessed level of preparation in six different areas. Almost all feel at least adequately prepared with respect to their science knowledge in other areas and the applications of physics to everyday experience. However, only two-thirds feel adequately or well prepared in recent developments in physics.
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01.50.-i Educational aids
01.40.ek Secondary school

F = qv×B:v is with Respect to What?

Kent W. Scheller and Thomas J. Pickett

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 169 | Cited 1 time

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In introductory physics classes, we typically introduce the magnetic force, F = qv × B, on a moving charge and its vector nature using a right-hand rule, as described by numerous textbooks.1–4 When presented to students, it is often assumed that the velocity of the charge used in this calculation is relative to the magnetic field in which it travels. Previously5–6 the relativity of the magnetic force has been discussed to show that v is not with respect to the magnetic field. Here we demonstrate with a couple of Gedanken experiments the actual relativity of the magnetic force and to what the charge's velocity is relative.
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01.50.-i Educational aids
03.30.+p Special relativity
03.50.De Classical electromagnetism, Maxwell equations
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Yo-yo Pull Demonstration

William Layton

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 172

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A popular demonstration involves placing a yo-yo on a level table and gently pulling the string horizontally when it is wrapped to come out below the center of the yo-yo's axis. Students are then asked to predict which way the yo-yo will move.1 A similar demonstration is performed with a tricycle by pulling forward on a pedal with the pedal down in its lowest position.2,3 As well as pulling the yo-yo horizontally, often the string is lifted until the angle it makes with the table causes no motion. This occurs when the line extended from the string intersects the point of contact of the yo-yo with the table.4 This paper describes an apparatus that extends these demonstrations to the situation where the force pulling the yo-yo is still horizontal yet is below the level of the table.
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01.50.My Demonstration experiments and apparatus
45.20.da Forces and torques

Discrepant Results in a 2-D Marble Collision

Peter Kalajian

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 173

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Video analysis of 2-D collisions is an excellent way to investigate conservation of linear momentum. The often-desired experimental design goal is to minimize the momentum loss in order to demonstrate the conservation law. An air table with colliding pucks is an ideal medium for this experiment, but such equipment is beyond the budget of many schools. Substituting marbles on a table for air pucks introduces angular momentum and sliding friction so that simple video analysis will demonstrate that linear momentum is not conserved.1,2 Nevertheless, these labs offer students insights into the real-world application of physics. During a recent classroom trial, an unexpected result forced my students to think creatively and critically about what happened in the experiment.
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01.50.My Demonstration experiments and apparatus
45.20.df Momentum conservation
46.55.+d Tribology and mechanical contacts
01.50.ff Films; electronic video devices

Ten Things You Should Do with a Tuning Fork

James Lincoln

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 176

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Tuning forks are wonderful tools for teaching physics. Every physics classroom should have several and every physics student should be taught how to use them. In this article, I highlight 10 enriching demonstrations that most teachers might not know, as well as provide tips to enhance the demonstrations teachers might already be doing. Some of these demonstrations have appeared in literature before, but this paper will serve as a collection of ideas that will be helpful for both the beginner and master teacher.
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01.50.My Demonstration experiments and apparatus
46.70.-p Application of continuum mechanics to structures
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Analyzing radial acceleration with a smartphone acceleration sensor

Patrik Vogt and Jochen Kuhn

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 182

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This paper continues the sequence of experiments using the acceleration sensor of smartphones (for description of the function and the use of the acceleration sensor, see Ref. 1) within this column, in this case for analyzing the radial acceleration.
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01.50.My Demonstration experiments and apparatus
06.30.Gv Velocity, acceleration, and rotation
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Washing the Plates

Boris Korsunsky, Column Editor

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 184

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Abstract Unavailable
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01.50.-i Educational aids
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Electricity and Magnetism

Diane Riendeau, Column Editor

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 185

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Thanks to Don Mathieson, Tulsa Community College, for this great collection of videos on electricity and magnetism. Don has included a list of questions to pose to the class.
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01.50.ht Instructional computer use
89.20.-a Interdisciplinary applications of physics
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Cascading failure in holiday lights

Aaron Schuetz

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 186

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multimedia

Abstract Unavailable
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01.50.My Demonstration experiments and apparatus
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Fermi Questions

Larry Weinstein, Column Editor

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 187

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Abstract Unavailable
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01.50.-i Educational aids
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Over 50 years of teaching physics — Some advice for young teachers

John L. Hubisz

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 188

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Many beginning teachers choose to teach because they were strongly influenced by favorite teachers and believe they can be successful if they attempt to emulate the practices they so admired in those teachers. I was fortunate to have several teachers whose practices I tried to bring into my teaching career that has spanned over 50 years. I've been successful in modifying some of those practices, and I would like to share with you the evolution of my teaching style as I attempted to meet the needs of my students.
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01.40.gb Teaching methods and strategies
01.50.-i Educational aids
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Climate Modeling Reports, Websites, Videos from the National Academy of Sciences, www.americasclimatechoices.org, nas-sites.org/climatemodeling/

Ken Huff

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 190

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Abstract Unavailable
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01.50.H- Computers in education
89.60.-k Environmental studies
92.70.Mn Impacts of global change; global warming
01.50.ff Films; electronic video devices

Nationwide Modeling Workshops Summer 2013, modelinginstruction.org/teachers/workshops-2013/

Wendy Heheman

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 190

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Abstract Unavailable
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01.50.-i Educational aids
01.40.ek Secondary school

Tutorials in Physics Science Making by Andy Elby, University of Maryland, tinyurl.com/WSEIbyMakeSense

Jane Jackson and Kathy Harper

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 190

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Abstract Unavailable
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01.50.-i Educational aids
01.40.-d Education

Perimeter Institute for Theoretical Physics director and theoretical physicist Neil Turok's 2012 CBC Massey Lecture videos, “The Universe Within: From Quantum to Cosmos”, itunes.apple.com/ca/album/cbc-massey-lectures-2012-by/id577245484

Dan MacIsaac, Column Editor

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 190

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Abstract Unavailable
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01.50.-i Educational aids
03.65.-w Quantum mechanics
42.00.00 Optics
45.20.D- Newtonian mechanics
98.80.-k Cosmology
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The Einstein Theory of Relativity: A Trip to the Fourth Dimension: Lillian R. Lieber, The Einstein Theory of Relativity: Lillian R. Lieber

Joe Heafner, Reviewer

The Physics Teacher -- March 2013 -- Volume 51, Issue 3, pp. 191

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Abstract Unavailable
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01.50.-i Educational aids
03.30.+p Special relativity
01.30.Vv Book reviews
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