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Buoyancy and Newton’s Third Law of Motion

Ernie McFarland University of Guelph

This article is excerpted from Physics in Canada, Volume 61, No. 2, (2005), pg. 87-89, with permission of the Canadian Association of Physicists (CAP).

In recent years the active engagement of students in physics classes has become increasingly common, especially with the publication of Eric Mazur’s book “Peer Instruction” (Prentice Hall, 1997). A frequently used format is to pose a multiple-choice question, and ask the students to discuss the question in small groups and vote on the possible answers by a show of hands or computerized remote-control technology (“clickers”). This basic approach can be used with a question about the possible outcomes of a lecture demonstration. The instructor shows the demonstration apparatus and states what will be done with it, but does not perform the demonstration nor indicate what the result will be. Students discuss the possible outcomes and vote on them, and then the demonstration is completed to show what actually happens, and the relevant physics is discussed. Read More...

Mystery of a Pulled Spool

Tetyana Antimirova, Department of Physics, Ryerson University

One of the ubiquitous simple physics demos that works equally well for all audiences from small children to the students in the introductory mechanics course is a plastic or wooden spool (or yo-yo) with a string wound around it. A virtually no-cost version of the “demo equipment” is a spool of common household sewing thread. Being curious, I did a Google search on yo-yo, and the search produced about 120,000,000 results! Read More...

Videos of Nonlinear Self-organizing Phenomena

Stephen Morris, Department of Physics, University of Toronto

Many of the ordered structures that we see in the natural world are self-organized in the sense that they emerge spontaneously from the normal operation of the underlying laws of physics, but in a way which is not at all obvious from those laws, and with some regular order which is not due to external guiding forces. Ripples on the sand at the beach (Fig. 1) are an example; somehow the action of the turbulent waves on the individual grains conspires to form the ripples, a highly organized patterned state. The wavelength of the ripples is not at all obvious in the basic physics of water-sand interaction. Read More...

GPS Meets Einstein

Damian Pope, Senior Manager of Outreach Perimeter Institute for Theoretical Physics

Column Editor’s Note: The author of this article presented a fascinating talk about this topic at the 2010 OAPT Conference. Via the weblink provided in the article, readers can obtain access to a very useful student activity that demonstrates the importance of relativity in the operation of GPS.

The Global Positioning System (GPS) is one of the twentieth century’s greatest engineering marvels. Today, it’s the backbone of billions of dollars of economic activity. It’s used by a vast array of occupations including farmers, construction workers, doctors and even professional athletes. And all this comes on top of the more familiar personal applications like satellite navigation in cars and for hiking.

As well as being immensely practical, the GPS also involves some pretty cool physics — even, strangely enough, Einstein’s theory of relativity. Read More...
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