Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 55, Number 9
Friday–Saturday, October 15–16, 2010; Ogden, Utah
Session H4: Education II |
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Chair: Adam Johnston, Weber State University Room: 404B |
Saturday, October 16, 2010 9:00AM - 9:12AM |
H4.00001: Basic biophysics as a pedagogical tool Gus L.W. Hart Some of the most basic processes of biology (e.g., diffusion and viscous flow) can be explained using physics learned in the lower-division calculus-based physics courses. Most of these processes do not even require an appeal to basic quantum mechanics. Thus, basic biophysics provides an interesting ``capstone'' for first-year physics (and another chance to get a feel for entropy!). I will discuss several examples showing how simple physics is at work in interesting biology. [Preview Abstract] |
Saturday, October 16, 2010 9:12AM - 9:24AM |
H4.00002: Acoustical characterization of exploding hydrogen-oxygen balloons Julia A. Vernon, Kent L. Gee, Jeffrey H. Macedone Exploding balloons are popular demonstrations in introductory chemistry and physical science classes and as part of outreach programs. However, as impulsive noise sources, these demonstrations constitute a possible hearing damage risk to both the demonstrator and the audience. To study the peak levels generated and other waveform and spectral characteristics, measurements of various hydrogen and hydrogen- oxygen balloons were made in an anechoic chamber at Brigham Young University. Condenser microphones (6.35-mm and 3.2-mm) were placed at various angles and distances from the balloon and time waveform data were collected at a sampling frequency of 192 kHz. For all balloon sizes tried, hydrogen-only balloons were found to produce peak sound pressure levels less than 140 dB at distances greater than or equal to 2 m. On the other hand, large (but reasonably sized) hydrogen-oxygen balloons can result in peak levels reaching 160 dB at a distance of 2 m, which constitutes a significant hearing risk for unprotected listeners at typical distances. These findings and other waveform and spectral features that help characterize the balloons as acoustic sources are discussed. [Preview Abstract] |
Saturday, October 16, 2010 9:24AM - 9:36AM |
H4.00003: A demonstration of acoustic shock wave propagation Michael B. Muhlestein, Kent L. Gee, Jeffrey H. Macedone High-amplitude sound requires nonlinear theory in order to properly describe waveform propagation. A common chemistry demonstration, an exploding gas-filled balloon, has been found to be a simple and effective way to verify nonlinear evolution predicted by the Earnshaw solution to the Burgers equation coupled with weak-shock theory. Measurements of acetylene- oxygen balloon explosions have been performed in an anechoic chamber with microphones placed at various distances from the balloon. Predicted and measured pressure levels show significant positive correlation. The results show that use of these demonstrations can be extended beyond introductory chemistry classes into graduate courses in physical acoustics. [Preview Abstract] |
Saturday, October 16, 2010 9:36AM - 9:48AM |
H4.00004: Stability of Inverted Pendulum and Heisenberg Uncertainty Principle Jeremy Redd, Alexander Panin Classical inverted pendulum can stay in the position of its unstable equilibrium (upside-down) indefinitely. However, due to the Heisenberg uncertainty principle no object can have both its position and its momentum to be absolutely certain at the same time. This fundamental principle applies to inverted pendulum resulting in impossibility to have even an unstable equilibrium. As a consequence, inverted pendulum has only a finite time to stay near its classical equilibrium position before it falls. Surprisingly, this time for a macroscopic-size pendulum (say, a pen on its tip) is only a few seconds long. In this presentation we analyze the time scales of ``quantum mechanical instability'' of inverted pendula of various lengths to see how quantum mechanics interferes with the behavior of classically-macroscopic objects. [Preview Abstract] |
Saturday, October 16, 2010 9:48AM - 10:00AM |
H4.00005: Modeling real-life pendula Jeremy Redd, Alexander Panin Since being introduced into the theory of damped oscillations, we use linear differential equation to model various oscillating systems including a pendulum. But real world pendula are not linear systems (even when the amplitude of oscillations is small). For example, air drag on a real size pendulum (from a few cm to a few meters in length) is quadratic rather than linear (by velocity), and a friction in a pivot point is often dominated by a static (rather than velocity-dependant) term. As a consequence, the decay patterns of real pendula are usually different than a classic exponent. This can be often seen when students perform pendulum lab using computer interface. By including air drag, air viscosity and static friction into the equation of oscillations we obtained very realistic model of real pendula. A comparison of the results of such model with experiments are discussed in the presentation. [Preview Abstract] |
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