These brief summaries are designed to help readers easily see which articles will be most valuable to them. The online version contains links to the articles.
Regular readers will note the temporary increase in the length of the journal. Since mid-May, submissions have been up by about 35%. We live in interesting times.
Energy cost of flight
Sanjoy Mahajan
This paper presents a simple model for the energy used in flight, understandable with only introductory mechanics. The lift and drag forces combine to yield a speed at which efficiency is maximized.
A LEGOTM dynamic force “macroscope”
D. Taylor, H. Smaje, and P. Moriarty
Instructions are given for the low-cost construction of a macroscopic analog of an atomic force microscope that demonstrates many of the principles of AFM microscopy, using LEGOs, magnets and an Arduino microcontroller. The construction is a multifaceted laboratory experience for advanced undergraduates, and the device is useful for illustrating AFM in courses and in outreach.
Analog implementation of a Hodgkin–Huxley model neuron
George H. Rutherford, Zach D. Mobille, Jordan Brandt-Trainer, Rosangela Follmann, and Epaminondas Rosa, Jr.
A circuit that mimics the action potential and ion channels of a neuron is useful for both pedagogical and research purposes. The article presents a simple implementation of such a circuit, requiring only basic background in electronics and the physics of neurons.
Learning-assistant-supported active-learning in a large classroom
Vera Margoniner, Jérôme Bür, and Matthew Block
Methods and results are presented from experiences using student learning assistants in active learning approaches to calculus-based mechanics at a public university, with evidence of greater learning gains. This work may be of interest to those considering changes in teaching methods.
Flight and bounce of spinning sports balls
Jacob Emil Mencke, Mirko Salewski, Ole L. Trinhammer, and Andreas T. Adler
The motion of spinning sports balls is studied using a combination of analytical, numerical, and experimental techniques. Motion in both vacuum and air is considered, as well as flight and bouncing motion. Appropriate for undergraduates learning about projectile motion.
Collecting data with a mobile phone: Studies of mechanical laws such as energy and momentum conservation
Maximillian Hart and Mark G. Kuzyk
Mobile phone videos of pool-ball collisions yield rich data that can be analyzed in terms of not only the conservation of energy and momentum but also dissipative forces. Such experiments outside of campus can serve as a useful alternative when in-lab experiments are not practical.
Theoretical study of the geometrical non-linearity of the elastic properties of helical springs
Vladimir V. Ivchenko
By considering the torques from the force applied to a helical spring, a relationship of force and spring elongation is derived that goes beyond Hooke's law. This work can help undergrads beyond the first year appreciate nonlinearity.
Physical pendulum model: Fractional differential equation and memory effects
L. N. Gonçalves, J. Fernandes, A. Ferraz, A. G. Silva, and P. J. Sebastião
The physical pendulum is studied with consideration of details related to hysteresis, entrainment of air mass, etc. Of particular interest is the use of fractional derivatives to represent memory effects. The material is most appropriate for advanced undergrads.
A completely algebraic solution of the simple harmonic oscillator
M. Rushka and J. K. Freericks
This paper presents a full algebraic derivation of the wavefunctions of the simple harmonic oscillator, appropriate for either undergraduate or graduate classes in quantum mechanics. This completely algebraic approach avoids introducing derivative operators and solving differential equations. A historical account of the operator method for the simple harmonic oscillator is also given.
Landau level, edge states, and gauge choice in 2D quantum dots
Asadullah Bhuiyan and Frank Marsiglio
Probability densities of quantum states ought to be gauge invariant, but this invariance can be hard to see. Eigenstates in both circular and square quantum dots in perpendicular magnetic fields are used to explore this gauge invariance, in a paper appropriate for upper-level undergraduate and introductory graduate level quantum mechanics instruction.
Exploring delay dynamics with a programmable electronic delay circuit
Edgar Perez, Colleen Werkheiser, Alex Striff, and Lucas Illing
Delay circuits enable the exploration of nonlinear effects and chaos, but existing circuits that can provide ∼100 ms delays are expensive or limited to AC signals. This paper, appropriate for advanced undergraduates, gives plans for a programmable delay circuit based on an Arduino Due and illustrates its use in exploring circuit dynamics.
Fluorescence lifetime measurements with simple correction for instrument temporal response in the advanced undergraduate laboratory
Eduardo Gonzalez, Seong J. Park, and David M. Laman
Undergraduates can measure and correct for instrument response, allowing nanosecond luminescence lifetimes to be measured with standard equipment in the advanced laboratory.
A simpler graphical solution and an approximate formula for energy eigenvalues in finite square quantum wells
F. M. S. Lima
For the energy levels in a finite quantum square well, an approximation method is presented that is accurate even for very deep or shallow wells, only requires a pocket calculator, and is appropriate for an introductory quantum course.
Comment on “The negative flow of probability” [Am. J. Phys. 88, 325–333 (2020)]
Arseni Goussev
A recent AJP paper had shown that the flow of probability for a Gaussian wave packet can be in the direction opposite to that of the wave packet itself. In an analysis appropriate for a junior-level quantum mechanics course it is shown that this quantum effect is analogous to a classical effect.