Matthew J. Moelter

Computational problems in introductory physics: Lessons from a bead on a wire

Thomas J. Bensky et al. — Thu, 14 Mar 2013 15:50:26 PDT

We have found that incorporating computer programming into introductory physics requires problems suited for numerical treatment while still maintaining ties with the analytical themes in a typical introductory-level university physics course. In this paper, we discuss a numerical adaptation of a system commonly encountered in the introductory physics curriculum: the dynamics of an object constrained to move along a curved path. A numerical analysis of this problem that includes a computer animation can provide many insights and pedagogical avenues not possible with the usual analytical treatment. We present two approaches for computing the instantaneous kinematic variables of an object constrained to move along a path described by a mathematical function. The first is a pedagogical approach, appropriate for introductory students in the calculus-based sequence. The second is a more generalized approach, suitable for simulations of more complex scenarios.

The implications of a robust curriculum in introductory mechanics

Chance Hoellwarth et al. — Thu, 14 Jul 2011 10:56:42 PDT

We have developed a curriculum for introductory mechanics that emphasizes interactive engagement and conceptual understanding using the studio format. As previously reported, we have shown in three different quarters that the curriculum much improved the students’ conceptual understanding compared to the traditional course without significantly affecting the scores on a traditional final exam. Here we report the results for the entire three-year period during which the course was taught, 34 sections of the course were taught with 11 different instructors to over 1200 students. In each term, these sections had common exams, syllabus, and schedule. Student experiences were very similar in terms of activities. Student performance was measured using the force and motion conceptual evaluation or the force concept inventory; the average pre/post normalized gain was 0.59. There was no significant correlation with any instructor characteristics, including teaching experience, knowledge of interactive-engagement methods, and attitudes. Because the instructor characteristics are not important, it is the structure of the course that promotes the learning gains.

Exposing Students to the Idea that Theories Can Change

Chance Hoellwarth et al. — Tue, 12 Apr 2011 08:57:46 PDT

Helium-4 solid-liquid interface mobility and ultrasonic energy absorption mechanisms

M. B. Manning et al. — Thu, 22 Apr 2010 16:27:21 PDT

The first measurements of acoustic reflection, together with acoustic transmission at the solid-liquid interface of ⁴He, are used to determine the total relative acoustic energy absorption at the interface as a function of temperature. Based on these results, a new mechanism for the temperature dependence of the kinetics of growth and interface mobility is proposed.

Electric Potential in the Classical Hall Effect: An Unusual Boundary-Value Problem

Matthew J. Moelter et al. — Thu, 22 Apr 2010 16:23:18 PDT

The classical Hall effect presents a surprisingly unusual and challenging problem in electrostatics, with boundary conditions that are not of Dirichlet, Neumann, or of mixed Dirichlet and Neumann type. These unusual boundary conditions create several difficulties not normally encountered in standard problems, and ultimately lead to expansion of the electric potential in a nonorthogonal basis set. We derive the boundary conditions for the potential in a rectangular geometry, construct a solution for the potential, and discuss the relation between this problem and problems of the standard mixed type. We also address a commonly encountered misconception about the current distribution.

Demountable Piezoelectric Transducer Holder for Use at Low Temperatures

Matthew J. Moelter et al. — Thu, 22 Apr 2010 16:23:18 PDT

We present a design for a piezoelectric transducer holder for use at low temperatures, which is easily constructed and assembled. Improved acoustic signals with "ringing" eliminated were reliably obtained. The standard problems of demountability, electrical integrity, and leak tightness in the presence of liquid helium at moderate pressures were resolved.

Plastic Deformation, Vacancy Diffusion, and Vacancy Delocalization in bcc ³He

Matthew J. Moelter et al. — Thu, 22 Apr 2010 16:23:17 PDT

The plastic deformation of bcc ³He crystals has been studied near the melting curve, in the temperature range 0.65 K ≤T≤.17 K, and for strain rates, ɛ˙, from 2x10^-6 to 2x10^-4 sec^-1. The resulting relations between strain rate and stress, at a given temperature, are accounted for in terms of dislocation climb and vacancy diffusion in the solid He. The temperature dependence of the strain rate at a given stress indicates that a nonclassical mechanism underlies the deformation process. The vacancy diffusion coefficient in bcc ³He, as a function of temperature, is deduced from these results, and an energy bandwidth for delocalized vacancies of 0.24±0.05 K is obtained through a fit to theoretical predictions.

A Child's Flashlight and RC Circuit Concepts

Matthew J. Moelter et al. — Thu, 22 Apr 2010 16:23:16 PDT

Effects of Second Sound on Acoustic Trasmission at the Solid-Liquid ⁴He Interface

Matthew J. Moelter et al. — Thu, 22 Apr 2010 16:23:16 PDT

We have calculated the reflection and transmission coefficients of acoustic waves propagating across a solid-liquid interface of ⁴He, using an extension of the treatment of Castaing and Nozières in which we include pressure changes associated with second sound. These calculations account well for the experimental results obtained over the temperature range 0.83 K≤ T ≤1.46 K and provide an alternative explanation to the one we offered previously for the lack of agreement between experiment and the theory of Castaing and Nozières.

A Direct Comparison of Conceptual Learning and Problem Solving Ability in Traditional and Studio Style Classrooms

Chance Hoellwarth et al. — Thu, 22 Apr 2010 16:23:15 PDT

We present data on student performance on conceptual understanding and on quantitative problem-solving ability in introductory mechanics in both studio and traditional classroom modes. The conceptual measures used were the Force Concept Inventory and the Force and Motion Conceptual Evaluation. Quantitative problem-solving ability was measured with standard questions on the final exam. Our data compare three different quarters over the course of 2 years. In all three quarters, the normalized learning gain in conceptual understanding was significantly larger for students in the studio sections. At the same time, students in the studio sections performed the same or slightly worse on quantitative final exam problems.

Hands-On Phasors and Multiple-Slit Interference

Rand S. Worland et al. — Thu, 22 Apr 2010 16:23:15 PDT

A Laboratory-based Nonlinear Dynamics Course for Science and Engineering Students

Nilgun Sungar et al. — Thu, 22 Apr 2010 16:23:14 PDT

We describe the implementation of a new laboratory-based interdisciplinary undergraduate course on nonlinear dynamical systems. Geometrical methods and data visualization techniques are especially emphasized. A novel feature of the course is a required laboratory where the students analyze the behavior of a number of dynamical systems. Most of the laboratory experiments can be economically implemented using equipment available in many introductory physics microcomputer-based laboratories.

"Hands-On" Epicycles and Retrograde Motion

Matthew J. Moelter et al. — Thu, 22 Apr 2010 16:23:14 PDT

Paper or Plastic?

Matthew J. Moelter — Thu, 22 Apr 2010 16:23:13 PDT

Letter to the Editor.

Two-Dimensional Pendulum Experiments Using a Spark Generator

Rand S. Worland et al. — Thu, 22 Apr 2010 16:23:12 PDT

Student understanding of the superposition of perpendicular harmonic oscillators can be enhanced using a spark generator to record position-versus-time data for smallamplitude pendulum motion in two dimensions. Our students have used this arrangement to analyze the motion of a spherical pendulum and a “Y-suspended” (Blackburn) pendulum that has two effective lengths.