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Carl Mungan, United States Naval Academy
The December 2015 issue of The Physics Teacher has an interesting article on page 518 explaining that giraffes drink not by repeatedly filling their mouths with water and raising their heads, nor by siphoning water up from their mouths to their stomachs like drinking straws, but rather by pumping water into their esophagus through two valves. On page 550 of the same issue there is a useful analysis of the key role played by the motional emf generated in the familiar demonstration of a current-carrying wire jumping out of a magnetic field.
An article on page 787 of the September 2015 issue of the American Journal of Physics provides an introductory-level derivation and discussion of the Boltzmann function from a theoretical, computational, and experimental point of view. I plan to try some of their arguments out this Spring in my introductory majors course. I also appreciated the analysis on page 21 of the January 2016 issue of the “world’s simplest electric train” YouTube video.
Article 065044 in the November 2015 issue of the European Journal of Physics points out a flaw in Galileo’s thought experiment proving that objects in vacuum cannot fall with differing speeds. If they did, he asked, what would happen if two stones of differing weights were tied together: would the combination fall faster or slower than the heavier stone alone? The flaw is that Galileo’s argument neglects the tension in the string tying the stones together. Article 065047 in the same issue examines rolling friction and mechanical energy dissipation for a ball rolling down an inclined plane. The journal can be accessed at http://iopscience.iop.org/journals.
Page 1111 of the December 2015 issue of Resonance has a nice review of the effects of radiative transfer in nature such as when viewing the sun, sky, or clouds. The issue can be freely accessed at http://www.ias.ac.in/listing/articles/reso/020/12. (Note the minor figure erratum for this article at http://www.ias.ac.in/article/fulltext/reso/021/01/0109-0109.)
Page 1604 of the October 2015 issue of the Journal of Chemical Education discusses the coming redefinition of the kilogram in the SI system of base units in terms of the Planck constant.
Article 020137 in Physical Review Special Topics—Physics Education Research considers whether or not it is helpful for students to decompose forces into component vectors that are drawn directly on a free-body diagram. Such diagrams end up with many arrows on them, leading to opportunities for errors and confusion about the fundamental meaning of Newton’s laws.