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Authors:Leontýna Šlégrová, Jan Šlégr Abstract: American Journal of Physics, Volume 90, Issue 5, Page 359-364, May 2022. Although the inaccurate explanation of lift based solely on the Bernoulli equation can still be found in textbooks, there are many places where interested readers can gain a correct understanding. However, it is complex and involves several physical phenomena. In this paper, we describe a simple device that can be used in teaching to support the understanding of the correct mechanism of the generation of lift either during lecture demonstrations or in undergraduate laboratory measurements. Citation: American Journal of Physics PubDate: 2022-04-21T02:45:13Z
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Authors:Abdulaziz M. Aljalal Abstract: American Journal of Physics, Volume 90, Issue 5, Page 373-379, May 2022. A typical Fabry–Pérot diode laser is used to study the relationship between the laser spectrum and the interference signal obtained from a Michelson interferometer. The interference signal is measured over a range of path length differences of a few centimeters, and the laser spectrum is obtained with a spectrometer of a high resolution of 0.005 nm. Contrary to the laser datasheet, the laser is found to have several longitudinal modes even at high injection currents well above the threshold current. A simple model based on treating the laser's longitudinal modes as pure sinusoidal waves is derived and successfully used in modeling the complex and repetitive interference signal. The spectral spacing and the laser cavity length can be found from the interference signal without the need to use a spectrometer, provided that the interference signal is measured over a long enough range of path length differences. Citation: American Journal of Physics PubDate: 2022-04-21T02:45:13Z DOI: 10.1119/5.0062798
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Authors:Mario Belloni, Craig Bohren, Harvey Gould, Raina Olsen, Beth Parks, Donald Salisbury, Jan Tobochnik Abstract: American Journal of Physics, Volume 90, Issue 5, Page 325-326, May 2022.
Citation: American Journal of Physics PubDate: 2022-04-21T02:45:12Z DOI: 10.1119/5.0092373
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Authors:Josefina María Silveyra, Juan Manuel Conde Garrido Abstract: American Journal of Physics, Volume 90, Issue 5, Page 365-372, May 2022. Representing components combined in series or parallel as a single equivalent component is a powerful tool for simplifying systems, both in mechanics and in electrical circuits. When combining inductors, the effect of mutual inductance decreases or increases the total inductance of the system, depending on the coupling factor between the inductors and on how they are connected. The analysis of mutually coupled inductors can be complex and is often avoided, obscuring the underlying physics. Here, we discuss the dependence of the equivalent inductance on the coupling factor for two parallel-connected inductors with linear magnetic core and negligible resistance. By analyzing the current distribution in each coil, we show that the so-called aiding and opposing arrangements are more complicated than is frequently assumed. We recommend avoiding these terms and calling them instead aligned and anti-aligned arrangements. Citation: American Journal of Physics PubDate: 2022-04-21T02:45:12Z DOI: 10.1119/5.0067939
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Authors:Giorgio Mantica Abstract: American Journal of Physics, Volume 90, Issue 5, Page 380-393, May 2022. This paper describes a deterministic dynamical model of the epidemic spreading of disease. We introduce fundamental concepts from nonlinear dynamics and statistical physics, and use computer simulations that can be implemented by advanced undergraduate and by graduate students. It is shown that the model can describe real-world phenomena during an epidemic. Due to its simplicity and flexibility, the model is also a useful tool for research. Citation: American Journal of Physics PubDate: 2022-04-21T02:45:11Z DOI: 10.1119/5.0082825
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Authors:Beth Parks, White Gary Abstract: American Journal of Physics, Volume 90, Issue 5, Page 327-327, May 2022.
Citation: American Journal of Physics PubDate: 2022-04-21T02:45:10Z DOI: 10.1119/5.0092653
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Authors:B. Cameron Reed Abstract: American Journal of Physics, Volume 90, Issue 5, Page 394-396, May 2022. An isotropic sphere or shell of matter can be regarded as acting as a point mass at its center so far as its gravitational force on an external test mass is concerned. This is well-known, but what is often not appreciated is that this behavior also holds for a central potential of the harmonic form V(r) ∼ r2. This paper proves this assertion and shows that only the gravitational and harmonic potentials possess this property. Citation: American Journal of Physics PubDate: 2022-04-21T02:45:10Z DOI: 10.1119/5.0072584
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Authors:Martín Monteiro, Arturo C. Martí Abstract: American Journal of Physics, Volume 90, Issue 5, Page 328-343, May 2022. This Resource Letter provides a guide to the literature on teaching experimental physics using sensors in tablets, smartphones, and some specialized devices. After a general discussion of hardware (sensors) and software (apps), we present resources for experiments using mobile-device sensors in many areas of physics education: mechanics, oscillations and waves, optics, electromagnetism, matter, modern physics, and astronomy. Citation: American Journal of Physics PubDate: 2022-04-21T02:44:58Z DOI: 10.1119/5.0073317
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Abstract: American Journal of Physics, Volume 90, Issue 5, Page 397-400, May 2022.
Citation: American Journal of Physics PubDate: 2022-04-21T02:44:58Z DOI: 10.1119/5.0086215
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Authors:R. Mathevet, N. Lamrani, L. Martin, P. Ferrand, J. P. Castro, P. Marchou, C. M. Fabre Abstract: American Journal of Physics, Volume 90, Issue 5, Page 344-350, May 2022. We present a detailed analysis of a smartphone pendulum, part of which was given as a homework assignment to first-year undergraduate students. We took care in the design and construction of the pendulum itself to draw maximum benefit from the high quality of the embedded sensors. Our students build a pendulum and analyze their data using the damped harmonic oscillator model. We introduce them to residue analysis to make them aware of slight nonlinearities in both the restoring and damping forces. Beyond what we ask our students, we present here results of numerical analyses to quantify these nonlinearities and demonstrate that aerodynamic drag contributes quite significantly to damping. We finally discuss our pedagogical experience using this assignment in the classroom. Citation: American Journal of Physics PubDate: 2022-04-21T02:44:57Z
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Authors:Douglas A. Kurtze Abstract: American Journal of Physics, Volume 90, Issue 5, Page 351-358, May 2022. When ice melts from a large ice sheet and the melt water runs into the ocean, global-mean sea level rises but, surprisingly, local sea level near the ice sheet may well drop. This is largely because the loss of mass reduces the gravitational pull of the ice sheet. We present a simple, analytically tractable model to illustrate this effect. We look first at a flat earth with a circular continent containing an ice sheet that is modeled as a point mass at its center and then extend the calculation to a rigid spherical non-rotating earth. With a bit more mathematical sophistication, we then carry out calculations for somewhat more realistic ice distributions and include the additional gravitation of the mass of displaced sea water. We give numerical results for the “fingerprint” of sea level change resulting from a 1000-Gt (1015-kg) loss of ice on a rigid, non-rotating earth, with parameter values appropriate to the Greenland and Antarctic ice sheets. Citation: American Journal of Physics PubDate: 2022-04-21T02:44:57Z DOI: 10.1119/5.0067924
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Authors:Daniel F. Styer Abstract: American Journal of Physics, Volume 90, Issue 5, Page 396-396, May 2022.
Citation: American Journal of Physics PubDate: 2022-04-21T02:44:54Z DOI: 10.1119/5.0090247