Browsing the Journals
- Giovanni Organtini's model of a transistor as a flush toilet on page 221 of the April 2012 issue of The Physics Teacher is cute. The May 2012 issue of the American Journal of Physics has a theme on astronomy with many helpful articles for nonastrophysicists like myself: An explanation on page 376 of why the expansion of the universe does not result in the expansion of the size of atoms and other bound systems; a discussion on page 539 of a better way to explain star colors than using Wien's law; and a short but provocative calculation on page 417 that uses the uncertainty principle to estimate the time it takes for a pencil balanced on point to fall over.
- On page 197 of the March 2012 issue of Physics Education, a nice explanation is provided of why modeling radioactivity by throwing 1000 dice and removing the ones that shows a 6 leads to a half-life that is systematically low compared to theory. The problem is that radioactive nuclei decay continuously while the dice "decay" in discrete steps as they are thrown. Other nice papers in the same issue is the discussion on page 152 of inverting a partly filled cup of water covered with a card and observing that the water does not all spill out, and a quantitative analysis on page 169 of a hanging rope slipping around a frictionless peg in terms of an Atwood machine with variable masses. The journal can be accessed at http://iopscience.iop.org/journals.
- The same webpage also gives a link to the European Journal of Physics. On page 439 of the March 2012 issue, the melting ice-cube puzzle is discussed: When an ice cube floating in a glass of water melts, what happens to the water level in the glass? A previous publication shows the answer is it rises if we include the loss of buoyant force on the part of the ice that was above the water line. But this new paper shows the answer is it drops if we also include the thermal contraction due to the heat required to melt the ice. On page 467 of the May 2012 issue, a nice discussion appears about how to avoid artificial infinities when calculating the electrostatic potential of an infinite line charge.
- There is a vigorous debate in the letters in the April 2012 issue of the Journal of Chemical Education about whether it's time to retire the model of hybrid atomic orbitals.
- I appreciated Chunfei Li's model for how the bowling down a track down which a cart is rolling will lead to an apparent violation of conservation of mechanical energy in the March 2012 issue of the Latin-American Journal of Physics Education.
- One of the reasons I love reading educational physics articles is that they often force me to rethink familiar physics explanations for phenomena. An excellent example is the article by Héctor Riveros on page 52 of 2012 Issue 2 of the relatively new European Journal of Physics Education. He challenges explanations for three common demonstrations: that when the end of a ruler protruding from under a sheet of newspaper at the edge of a table is given a sharp blow it breaks because of air pressure on the sheet; that water rises into an inverted jar covering a burning candle in a tray of water because the candle consumes the available oxygen; and that a stream of water is attracted to an electrically charged balloon because water is polar.
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.