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

The article “Birds on power lines” in the July 2014 issue of the American Journal of Physics (http://scitation.aip.org/content/aapt/journal/ajp) discusses three effects related to a bird contacting a single high-voltage power line: capacitive charge transfer to the “spherical” bird even if it stands on one foot, and currents in the bird between its two feet due to its finite resistance and to the ac phase difference along the wire. The August issue has a paper on page 764 that analyzes the path that a block takes when it is given a push at some angle (relative to the straight “down” direction) on a rough inclined plane. Particularly interesting is the case when the incline is small enough that the block eventually comes to rest. Finally, the September issue has a PER paper that shows that a group of South Korean high school physics students who solved an average of 2200 physics problems each did not perform significantly better on exams than those who solved comparatively few. It is not helpful to simply grind through a large number of problems, but instead some of the students’ time should be spent learning the bigger picture of physics concepts and frameworks.

Page 349 of the September 2014 issue of The Physics Teacher (http://scitation.aip.org/content/aapt/journal/tpt) has a nice analysis (with convincing YouTube links) of why a heavy disk at the end of a rod is much easier to lift with one hand when the disk is spinning than when it is not. The October issue has one of my all-time favorite High School Photo Contest pictures on its cover. I only hope the young lady doing the “Orange Wave” did not choke on paint particles a few seconds after the camera snapped the portrayed shot. I thought the article about writing “Letters home as an alternative to lab reports” made a convincing case and I may try it in my own classes. William Layton surprised me on page 426 by showing that a light bulb on the input side of an isolation transformer will go out if a similar bulb on the output side is unscrewed from its socket. I was similarly amazed to read on page 428 that a tuning fork with one tine covered is louder than with it uncovered. Lastly, my whole family had a fun time constructing a closed loop from a single strip of paper that can lift a bucket of water when held by a single finger, purely by folding the strip in the manner explained on page 436.

The July 2014 issue of Physics Education has an article that experimentally tests the Bernoulli equation for water flowing out of a jug on page 436. On page 390, the familiar problem of a ladder leaning against a wall is discussed, but this time with the floor smooth and the wall rough. Benacka has developed a new way to solve the Kepler problem without changing variables to u = 1/r in the July 2014 issue of the European Journal of Physics and presents an Excel spreadsheet to calculate the motion. Interesting articles in the September issue include measurement of the electric charge on a piece of Scotch tape pulled apart from another piece of tape, a simple derivation of the Boltzmann factor, and an analysis of a catenary without using the calculus of variations. Both journals are accessible at http://iopscience.iop.org/journals.

Page 1455 of the September 2014 issue of the Journal of Chemical Education at http://pubs.acs.org/toc/jceda8/91/9 has a simple derivation of shot noise in a photodiode or photomultiplier tube using the Poisson distribution.

The March 2014 issue of the Latin-American Journal of Physics Education (http://www.lajpe.org/) presents a model fitted to experimental data for the eddy current damping of a magnet oscillating through a hole in a metal disk on page 109.

Mazur’s group has published a study in Physical Review Special Topics – Physics Education Research at http://journals.aps.org/prstper/pdf/10.1103/PhysRevSTPER.10.020113 about the times that students take to respond to clicker questions. Response times for correct answers are shorter than times for incorrect answers, suggesting that instructors should end the polling at around the 80% response rate to cut down on the number of random guesses biasing the overall histogram of results.

Usually light pushes objects away due to the radiation pressure. Can it also attract them, creating an optical tractor beam? An article in Physical Review Letters suggests that it might, as a result of the ac Stark shifts, at http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.023601.

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.