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Sep 2011

Volume 49, Issue 6, pp. 324-400

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Physics From the News — Fukushima Daiichi: Radiation Doses and Dose Rates

A. A. Bartlett

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 330

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The nuclear disaster that was triggered by the Japanese earthquake and the following tsunami of March 11, 2011, continues to be the subject of a great deal of news coverage. The tsunami caused severe damage to the nuclear power reactors at Fukushima Daiichi, and this led to the escape of unknown quantities of radioactive material from the damaged fuel rods in the reactors and from the associated storage facilities for the fuel rods that had been removed from the reactors.
Show PACS
01.50.-i Educational aids
87.53.Bn Dosimetry/exposure assessment
28.41.Te Protection systems, safety, radiation monitoring, accidents, and dismantling
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High-Speed Video Analysis in a Conceptual Physics Class

Dwain M. Desbien

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 332 | Cited 2 times

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multimedia

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The use of probe ware and computers has become quite common in introductory physics classrooms.1 Video analysis is also becoming more popular and is available to a wide range of students through commercially available and/or free software.2,3 Video analysis allows for the study of motions that cannot be easily measured in the traditional lab setting and also allows real-world situations to be analyzed. Many motions are too fast to easily be captured at the standard video frame rate of 30 frames per second (fps) employed by most video cameras. This paper will discuss using a consumer camera that can record high-frame-rate video in a college-level conceptual physics class. In particular this will involve the use of model rockets to determine the acceleration during the boost period right at launch and compare it to a simple model of the expected acceleration.
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01.50.Pa Laboratory experiments and apparatus
45.40.Gj Ballistics (projectiles; rockets)
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.
FREE

Ring Falling into a Chain: No Magic — Just Physics

Michael Vollmer and Klaus-Peter Möllmann

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 335 | Cited 4 times

Online Publication Date: Aug 2011

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multimedia

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Magic tricks are very popular, and they can and should be used in teaching when the underlying principle is easily explained by physics. Such tricks often fall in the realm of hands-on experiments, which are considered to be potentially very effective in raising interest and motivating students.1 Unfortunately, many hands-on experiments are easy to do, but more difficult to explain. One of the reasons is that they often happen so fast that the underlying principle can only be guessed. Also, a magic trick can be disguised so that an observer cannot solve the puzzle with the naked eye. Quite often even regular camcorders do not provide the necessary time resolution. Fortunately, however, huge advances in microsystem technologies have recently led to the development of commercially available high-speed cameras that are relatively inexpensive. The low end of the price range is now at or below $300.2 Some models of the Casio Exilim series provide up to 1200 frames per second for reduced image size. The technology of such cameras has been extensively summarized elsewhere,3 and many nice examples of experiments recorded with high-speed imaging are under way.4 Here we present one example of a physics “magic trick” that is extremely easy to perform while giving stunning results. High-speed images (snapshots and movies) can nicely reveal the physics behind the trick.
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01.50.My Demonstration experiments and apparatus

Pepper's Ghost

Thomas B. Greenslade, Jr.

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 338

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Without applications of physics such as counter-weighted sets and backdrops, inclined planes, stage lighting instruments, and other mechanisms for deus ex machina, dramatic productions would revert to the words only—fine for Shakespeare and Becket, but not good for audiences who are accustomed to experiencing plays with the eye as well as the ear. Pepper's Ghost is a 19th-century stage illusion, based on basic optical principles, that can find its way into your introductory classroom.
Show PACS
01.50.-i Educational aids
42.70.Ce Glasses, quartz
42.25.Bs Wave propagation, transmission and absorption
42.25.Gy Edge and boundary effects; reflection and refraction
42.15.Eq Optical system design
42.15.Dp Wave fronts and ray tracing

Special Relativity in Week One: 4) Lack of Simultaneity

Elisha Huggins

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 340 | Cited 1 time

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This is our final article on teaching special relativity in the first week of an introductory physics course.1–3 One of the profound changes in our view of the world was Einstein's discovery of the lack of simultaneity. He illustrated this result with a thought experiment in which we observe a railroad car passing by us. We see the two ends of the car struck simultaneously by lightning bolts, but to someone riding inside the car, the lightning strikes were not simultaneous. My difficulty with this thought experiment is that while doing calculations, I have to go back and forth between two imagined points of view. To avoid this, I actually perform an experiment that involves two simultaneous events. then all we have to imagine is how the experiment looks to someone moving by us. Not only does the order of the two events depend on the direction of motion of the observer, but we can demonstrate that if information could travel faster than the speed of light, we could get answers to questions that have not yet been thought of.
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01.50.Pa Laboratory experiments and apparatus
03.30.+p Special relativity

Reanalyzing the Ampère-Maxwell Law

S. Eric Hill

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 343 | Cited 1 time

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In a recent TPT article,1 I addressed a common miscommunication about Faraday's law, namely, that introductory texts often say the law expresses a causal relationship between the magnetic fields time variation and the electric fields circulation. In that article, I demonstrated that these field behaviors share a common cause in a time-varying current density. From that, many readers may have rightly guessed at a symmetric conclusion: while the Ampère-Maxwell law is commonly said to express a causal relation between the electric fields time variation and the magnetic fields circulation, these field behaviors share a distinct, common cause. Together, Faraday's law and the Ampère-Maxwell law constitute half of Maxwell's laws that form a foundation for almost all of electricity and magnetism. By misrepresenting these two laws, introductory texts not only present students with unnecessary conceptual hurdles early in their physics educations but also leave them with enduring misunderstandings about the very foundation of electricity and magnetism. Fortunately, compared to what is commonly taught, the actual cause of these field variations is conceptually simpler and more consistent with what the students will have already learned in the introductory texts' own earlier chapters.
Show PACS
01.40.ek Secondary school
03.50.De Classical electromagnetism, Maxwell equations
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems

Lotus Effect Toy

Said Shakerin

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 346

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This is a short article about Aqua Drop, a toy that employs a superhydrophobic surface. After defining superhydrophobic surface, its occurrence in nature, and its importance in science and technology, I describe the toy, followed by several student activities that can be performed with the toy and easily found natural objects.
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01.50.Wg Physics of toys
01.50.My Demonstration experiments and apparatus

Racial and Gender Issues with Physics in the Pacific Region

Than Aung, Awnesh Singh, and Uma Prasad

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 349

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This paper examines the state of physics teaching and learning in the Pacific Island nations. How have things changed in teaching physics? We believe that some of the goals and many of the challenges faced today have changed very little over the years. This paper is purely based upon the authors' experiences in teaching physics at the first-year level at the University of the South Pacific (USP). USP is a typical medium-sized teaching and research university as compared to universities internationally. In the Pacific, it is the biggest university and is effectively serving the 12 Pacific Island nations. Consequently, the findings described here should represent the overall situation for the Pacific region. Perhaps some of our results will resonate with readers in other locations as well. Worldwide, university students often find studying physics to be very challenging, and only a small fraction of them choose physics as a major for their degree or as a career.1 Students at USP are not an exception, and here we describe the severity of the problem.
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01.50.-i Educational aids
01.75.+m Science and society
01.78.+p Science and government (funding, politics, etc.)
01.55.+b General physics

Cartoon by Alejandro Yegros

Alejandro Yegros

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 351

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Abstract Unavailable
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01.40.Fk Research in physics education

USAYPT Holds Annual February Tournament

Bruce Oldaker

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 352

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The United States Association for Young Physicists Tournaments (USAYPT) held its annual U.S. Invitational Young Physicists Tournament Feb. 4–5, 2011, at Oak Ridge Associated Universities Institute for Science Education, Oak Ridge, TN. Young physicists tournaments are theoretical and experimental research-based team competitions described more fully at the USAYPT website: www.usaypt.org. This year the problems were #1: Domino Wave, #2: Salt-Water Oscillator, #3: Magic Motor, and #4: Boiling Water.
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01.40.ek Secondary school
01.40.Fk Research in physics education
01.10.Hx Physics organizational activities

The Rolling Release Rulapult

Joseph West, Seth Ross, and James Flesher

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 353

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The “rulapult” is a low-cost, easy-to-construct, ruler-based catapult for use in the classroom. It is made from durable, inexpensive items that are easy to store. Most of the components can be found with a visit to one or two local stores. A set of 12 complete rulapults can be constructed for less than $150, including the one-time cost of the only tool needed for construction, a single handheld one-hole paper punch. The unit price per rulapult approaches $10.25 as the number of rulapults constructed becomes “large.” A rulapult can be constructed by a single middle school student in less than five minutes. Ping-Pong® balls or marshmallows are suggested for use as projectiles as they pose a minimal safety hazard. The range of a typical rulapult when firing a Ping-Pong ball is approximately 4.0 m, just right for classroom or hallway testing. The smaller (1-cm size) marshmallows have a range of about 5.0 m, but due to their “squishy” nature, the range is less consistent from shot to shot. For the rest of the discussion, it is presumed that the projectile is a Ping-Pong ball (the ball). The ball can easily knock over a large Styrofoam™ cup, but despite its impressive range and “knock-down power,” the rulers used are “limp” enough that a direct hit to your hand by the ruler will not cause noticeable pain or injury.
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01.50.Pa Laboratory experiments and apparatus
45.40.Gj Ballistics (projectiles; rockets)

An Improved Box Theater

Michael E. Huster

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 356

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While designing an optics lab for a conceptual physics course, I came across a “box theater” activity.1 The box theater is a pinhole camera obscura made from a box that students put over their heads and shoulders. I use the activity as a capstone experience to explain optical systems. (Classroom demonstrations of the camera obscura have been described by others.2) First, the students build and experiment with a camera obscura made from a plastic cup and a convex lens with a focal length of 7.5 cm, and then “wear” the box theater. The difficulty with the box theater is the dimness of the image. A cloth drape has to be hung from the bottom of the box around the shoulders of the students to prevent light leakage, and the students have to wait a few minutes for their eyes to adjust to the darkness.
Show PACS
01.50.My Demonstration experiments and apparatus
42.15.Eq Optical system design
42.79.Bh Lenses, prisms and mirrors
07.68.+m Photography, photographic instruments; xerography

Black and Hispanic Participation in High School Physics Still Low

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 356

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Abstract Unavailable
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01.40.-d Education

Optics Demonstration with Student Eyeglasses Using the Inquiry Method

Mark C. James

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 357

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A favorite qualitative optics demonstration I perform in introductory physics classes makes use of students' eyeglasses to introduce converging and diverging lenses.1 Taking on the persona of a magician, I walk to the back of the classroom and approach a student wearing glasses. The top part of Fig. 1 shows a glasses-wearing student who is farsighted in her left eye and has a slight astigmatism in her right eye.
Show PACS
01.50.My Demonstration experiments and apparatus
42.79.Bh Lenses, prisms and mirrors

A Simple Experiment to Explore Standing Waves in a Flexible Corrugated Sound Tube

Maria Eva Amorim, Teresa Delmira Sousa, P. Simeão Carvalho, and Adriano Sampaioe Sousa

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 360 | Cited 1 time

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Sound tubes, pipes, and singing rods are used as musical instruments and as toys to perform amusing experiments. In particular, corrugated tubes present unique characteristics with respect to the sounds they can produce; that is why they have been studied so intensively, both at theoretical and experimental levels.1–4 Experimental studies usually involve expensive and sophisticated equipment that is out of reach of school laboratory facilities.3–6 In this paper we show how to investigate quantitatively the sounds produced by a flexible sound tube corrugated on the inside by using educational equipment readily available in school laboratories, such as the oscilloscope, the microphone, the anemometer, and the air pump. We show that it is possible for students to study the discontinuous spectrum of sounds produced by a flexible corrugated tube and go even further, computing the speed of sound in air with a simple experimental procedure.
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01.50.Pa Laboratory experiments and apparatus

Wikis as a Teaching Tool in Physics Classrooms

Hashini E. Mohottala

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 363 | Cited 1 time

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The advances of the digital age have made the duty and responsibility of the professor more complex and involved. The Internet has made powerful and useful tools available to us to disseminate knowledge in an interesting and effective manner. In this article, I discuss one such tool: Wikispaces (wikis)—a set of interactive web pages that can be accessed and updated by a group of users using any web browser.1
Show PACS
01.40.gb Teaching methods and strategies
89.20.Hh World Wide Web, Internet

The “Green Lab”: Power Consumption by Commercial Light Bulbs

James A. Einsporn and Andrew F. Zhou

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 365

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Going “green” is a slogan that is very contemporary, both with industry and in the political arena. Choosing more energy-efficient devices is one way homeowners can “go green.” A simple method is to change home lighting from hot incandescent bulbs to compact fluorescent lights (CFLs). But do they really save energy? How do their illuminations compare? Even if the CFLs are more energy efficient, they still add to our pollution problem because of the mercury inside them. Light-emitting diodes (LEDs) could be the answer, but they are not available at our local stores. Can LEDs be made to screw right into a standard socket? How expensive are they? What are the power consumptions of so-called “60-W” and “100-W” CFL and LED light bulbs? These are the questions that are answered during this lab activity. Students measure the voltage and current for each of the three types of bulbs, and then calculate the electrical power required by each. An optional experiment is to set the light outputs of each bulb so they are equal in intensity, and then determine the power consumed. While not practical in the home, this experiment gives students an understanding of value for their buck.
Show PACS
01.50.Pa Laboratory experiments and apparatus
01.50.My Demonstration experiments and apparatus
88.05.Tg Energy use in lighting
85.60.Jb Light-emitting devices
FREE

Infrared Imaging for Inquiry-Based Learning

Charles Xie and Edmund Hazzard

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 368 | Cited 2 times

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Based on detecting long-wavelength infrared (IR) radiation emitted by the subject, IR imaging shows temperature distribution instantaneously and heat flow dynamically. As a picture is worth a thousand words, an IR camera has great potential in teaching heat transfer, which is otherwise invisible. The idea of using IR imaging in teaching was first discussed by Vollmer et al. in 2001.1–3 IR cameras were then too expensive for most schools. Thanks to the growing need of home energy inspection using IR thermography, the price of IR cameras has plummeted and they have become easy to use. As of 2011, the price of an entry-level handheld IR camera such as the FLIR I3 has fallen below $900 for educators. A slightly better version, FLIR I5, was used to take the IR images in this paper. As easy to use as a digital camera, the I5 camera automatically generates IR images of satisfactory quality with a temperature sensitivity of 0.1°C. The purpose of this paper is to demonstrate how these affordable IR cameras can be used as a visualization, inquiry, and discovery tool. As the prices of IR cameras continue to drop, it is time to give teachers an update about the educational power of this fascinating tool, especially in supporting inquiry-based learning.
Show PACS
01.50.Pa Laboratory experiments and apparatus
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.68.+m Photography, photographic instruments; xerography
44.00.00 Heat transfer

Flight Physics for Beginners: Simple Examples of Applying Newton's Laws

Vassilis Spathopoulos

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 373 | Cited 1 time

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Educators are constantly trying to find new ways of motivating their students. In subjects such as mechanics with a strong mathematical component, it is particularly important to devise real-life examples that can increase interest and student excitement. Aircraft flight is a topic that most young people find exciting. It therefore would seem reasonable to incorporate applications from the world of flight into an introductory physics course.
Show PACS
01.50.My Demonstration experiments and apparatus
45.05.+x General theory of classical mechanics of discrete systems
45.20.da Forces and torques
89.40.Dd Air transporation

Building Dynamic Conceptual Physics Understanding

Charlotte Trout, Scott A. Sinex, and Susan Ragan

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 377 | Cited 1 time

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Models are essential to the learning1 and doing of science, and systems thinking is key to appreciating many environmental issues. The National Science Education Standards2 include models and systems in their unifying concepts and processes standard, while the AAAS Benchmarks3 include them in their common themes chapter. Hyerle4 and Marzano5,6 argue for the importance of graphic organizers to student learning. In addition, there is a growing national interest in defining and implementing computational thinking for students.7 In the past 15 years, we have presented dozens of workshops to teachers who are interested in using the computational power of their computers in their classrooms.8–9 In addition to other programs, we use systems dynamics programs to encourage modeling in secondary science classrooms. The interface for these packages is a graphic organizer. In this article we will share some of our insights into the advantages of using such systems dynamics software with high school physics students.
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01.50.ht Instructional computer use
01.40.J- Teacher training

Motivating Calculus-Based Kinematics Instruction with Super Mario Bros

Jeffrey C. Nordine

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 380

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High-quality physics instruction is contextualized, motivates students to learn, and represents the discipline as a way of investigating the world rather than as a collection of facts and equations.1 Inquiry-oriented pedagogy, such as problem-based instruction, holds great promise for both teaching physics content and representing the process of doing real science.2 A challenge for physics teachers is to find instructional contexts that are meaningful, accessible, and motivating for students. Today's students are spending a growing fraction of their lives interacting with virtual environments, and these environments—physically realistic or not—can provide valuable contexts for physics explorations3–5 and lead to thoughtful discussions about decisions that programmers make when designing virtual environments. In this article, I describe a problem-based approach to calculus-based kinematics instruction that contextualizes students' learning within the Super Mario Bros. video game—a game that is more than 20 years old, but still remarkably popular with today's high school and college students.
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01.50.ht Instructional computer use
01.50.ff Films; electronic video devices
45.40.-f Dynamics and kinematics of rigid bodies
45.50.-j Dynamics and kinematics of a particle and a system of particles

Experiments Using Cell Phones in Physics Classroom Education: The Computer-Aided g Determination

Patrik Vogt, Jochen Kuhn, and Sebastian Müller

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 383

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This paper continues the collection of experiments that describe the use of cell phones as experimental tools in physics classroom education.1–4 We describe a computer-aided determination of the free-fall acceleration g using the acoustical Doppler effect. The Doppler shift is a function of the speed of the source. Since a free-falling objects speed is changing linearly with time, the Doppler shift is also changing with time. It is possible to measure this shift using software that is both easy to use and readily available. Students will use the time-dependency of the Doppler shift to experimentally determine the acceleration due to gravity by using a cell phone as a freely falling object emitting a sound with constant frequency.
Show PACS
01.50.Lc Laboratory computer use
01.50.Pa Laboratory experiments and apparatus
45.20.da Forces and torques
43.28.Py Interaction of fluid motion and sound, Doppler effect, and sound in flow ducts

Single-Concept Clicker Question Sequences

Albert Lee, Lin Ding, Neville W. Reay, and Lei Bao

The Physics Teacher -- September 2011 -- Volume 49, Issue 6, pp. 385

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Students typically use electronic polling systems, or clickers, to answer individual questions. Differing from this tradition, we have developed a new clicker methodology in which multiple clicker questions targeting the same underlying concept but with different surface features are grouped into a sequence. Here we present the creation, validation, and evaluation of clicker question sequences sufficient in number to populate a year of calculus-based introductory physics.
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01.50.-i Educational aids
02.30.Vv Operational calculus
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