Carl Mungan, United States Naval Academy
mungan@usna.edu

Edmond Levy discusses matrix methods for solving the coupled differential equations for a sequential chain of radioactive decays on page 909 of the December 2018 issue of the American Journal of Physics (http://aapt.scitation.org/journal/ajp). The same issue also has an article on page 934 titled “Will my student evaluations decrease if I adopt an active learning instructional strategy?” In half of the surveyed cases the answer is they actually increased, and in another third there was no change, and so instructors should not fear trying such teaching methods. On page 5 of the January 2019 issue, Alon Drory analyzes a rod thrown horizontally out of a moving train to show that accelerated objects cannot always be described as passing through a sequence of instantaneous comoving frames. The Computational Physics section in the same issue wrestles with the thorny issue of why multiplanetary solar systems do not collapse due to collisions between or ejections of planets.

The November 2018 issue of The Physics Teacher (http://aapt.scitation.org/journal/pte) has a terrific photo on its cover of a ring of ice crystals formed as a cup of hot water is flung around when the air temperature is –20°C. Another great photo on the last page shows the polarized transmission of skylight through a thin ice sheet after oblique reflection off a pool of water. A two-part article starting on page 516 of this issue discusses the physics of airplane lift in detail. I also enjoyed the personal reminiscences of falling in love with physics (“feezya”) as an Algerian middle-school student on page 559. An article on page 600 of the December issue helpfully explains the difference between plotting blackbody spectral intensity against frequency and wavelength by considering color bands rather than individual lines. In the January 2019 issue, an article on page 21 shows that experiments relating pressure to temperature using a Vernier sensor can be dramatically improved in accuracy by considering the extra volume of air trapped in the sensor and tubing. On page 40 of the same issue, Bob Hilborn provides a simple explanation of why potential energy (unlike kinetic energy) is a Galilean invariant.

Article 065203 in the November 2018 issue of the European Journal of Physics considers some puzzles associated with two capacitors connected in series via a resistor when the initial charges on the two capacitors are different. Article 015204 in the January 2019 issue analyzes the voltages and forces between multiple charged pithballs hanging by equal-length threads from a common point of attachment. I also found Bokor’s diagrammatic analysis of a relativistic rocket to be enlightenining in article 015603 of the same issue. Article 065004 in the November 2018 issue of Physics Education uses the uncertainty principle to estimate the Hawking temperature of a black hole. The well-known demonstration of the surprisingly large frictional force between interleaved books is reconsidered in article 015004 of the January 2019 issue. Both journals can be accessed online starting at http://iopscience.iop.org/journalList.

Lima has a helpful analysis of why the electric field at the surface of a charged conducting sphere is half of that just outside the sphere in the November 2018 issue of Resonance. It can be freely accessed at http://www.ias.ac.in/listing/issues/reso.

Peter Lang discusses limitations of the usual model of a conductor as ions in a gas of free electrons on page 1787 of the October 2018 issue of the Journal of Chemical Education. On page 1989 of the November issue, the quantum mechanical bound states of a negative hyperbolic secant squared potential are presented. In the same issue on page 2041, laser polarimetry is used to measure scattering from a solution in an undergraduate lab. The journal archives are at http://pubs.acs.org/loi/jceda8.

Article 020121 in Physical Review Physics Education Research at https://journals.aps.org/prper/pdf/10.1103/PhysRevPhysEducRes.14.020121 investigates shortcomings in student understanding of bipolar transistors.

Disclaimer – The articles and opinion pieces found in this issue of the APS Forum on Education Newsletter are not peer refereed and represent solely the views of the authors and not necessarily the views of the APS.