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December 8, 2009 The High Road/Low Road Demonstration, or Birds on a WireBy Jacob Cady and Chad A. Middleton, Department of Physical and Environmental Sciences, Mesa State College, Grand Junction, CO AbstractConsider two separate tracks of equal horizontal displacements and equal initial and final heights. One track remains at this initial height while the other angles down, levels out, and then angles back up in order to regain its original height. Question: If two identical balls are set rolling with equal initial speeds, which ball completes the track in a shorter time interval? In this manuscript, the dynamics of a ball on each track are analyzed using basic Newtonian mechanics. We calculate the time necessary to complete each path in terms of the parameters of the track and the initial velocities of the balls. We derive an expression for the time difference between the two tracks and compare this to data taken on a set of high road/load road tracks, hence demonstrating the fact that the ball traversing the low road always wins the race. Key Wordsconservation of energy, kinematics, moment of inertia, Newtonian mechanics, rolling without slipping
November 16, 2009 General Search for Stars with Rapid Optical Variations: Test FieldsBy E. Fagg, J. Park, K. Pearson, and R. Kehoe, Southern Methodist University, Dallas, TX AbstractWe present a search for stars exhibiting short time-scale optical light variations. Our search employs archival data taken by the ROTSE1 telephoto array in two eight degree fields of view. This is a test study considering two fields which overlap fields previously mined for variables, but with different data and search techniques. Each field was observed for approximately six continuous hours. We employ a general search strategy based on statistical properties of the observed light curves for each object. The analysis is sensitive to sources with variations < 0.25 day and > 0.1 mag and with mean magnitudes between 9.5 mag and 14 mag. We identify 42 variable stars with our search strategy. Of these, 17 were not found by comparison with catalogs of previously acknowledged variables. Within this sample, attempts at classification yield four W UMa systems and two ? Scu stars. The remaining eleven transient detections exhibit incomplete light curves and require further study for classification. Key WordsAstronomy, charged coupled devices (CCDs), eclipsing binary stars, light curves, magnitudes, pulsating stars, ROTSE telescopes, SIMBAD astronomical database, variable stars
August 31, 2009 Kayaking Physics: The Tipping AngleBy Daniel R. Rottinghaus and Chad A. Middleton Department of Physical and Environmental Sciences, Mesa State College, Grand Junction, CO AbstractWe apply basic physics to the rotational motion of a kayak in water to determine the angle at which the kayak will tip. Approximating the cross-section of the kayak as an ellipse, we apply Newtonian mechanics to the physical system and arrive at a set of coupled algebraic equations describing this critical angle. The equations are transcendental in nature and cannot be solved analytically. Using a numerical approach, we calculate the tipping angle for several values of the center of mass of the kayak-kayaker system. Key Wordsbuoyancy, center of mass, fluid mechanics, Newtonian mechanics, torques, transcendental equations
August 12, 2009 Global Behavior of the Radial Orbit InstablilityBy Paul A. Lanzel and Eric I. Barnes, Department of Physics, University of Wisconsin — La Crosse, AbstractA variety of evidence points to the existence of dark matter in the universe. As it is not directly observable with conventional astronomical techniques, we must rely on computer models to guide our understanding. We have created a suite of such models in order to observe and explain a specific behavior common to models of dark matter systems called the radial orbit instability (ROI). This instability changes self-gravitating systems from spherical to non-spherical shapes, with corresponding alterations to density and velocity distributions. The initial conditions of our models span a parameter space that is relevant to the radial orbit instability; we control the initial dynamical temperature, density profile, and velocity anisotropy in our models. We have found that in dynamically hot and warm systems, the radial orbit instability will be triggered if the initial velocity anisotropy is high enough. The exact amount of anisotropy required varies somewhat for different initial density profiles. Dynamically cold systems behave somewhat differently, but in general, less initial anisotropy is required to initiate the ROI as compared to hot and warm systems. Key Wordsastrophysics, computer simulation, dark matter, Newtonian gravitation, orbit stability, virial theorem
March 4, 2009 Time-resolved Photoelectron Spectroscopy and the Photoprotective Properties of AdenineBy Amanda N. Brouillette, N. L. Evans, William M. Potter, and Susanne Ullrich, Department of Physics and Astronomy, The University of Georgia, Athens GA Abstract
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