Measuring longitudinal wave speed in solids: two methods and a half

Three methods to analyse longitudinal wave propagation in metallic rods are discussed. Two of these methods also prove to be useful for measuring the sound propagation speed. The experimental results, as well as some interpretative models built in the context of a workshop on mechanical waves at the Graduate School for Pre-Service Physics Teacher Education, Palermo University, are described. Some considerations about observed modifications in trainee teachers' attitudes to utilizing physics experiments to build pedagogical activities are discussed

AN INTRODUCTION TO THE BOLTZMANN FACTOR BY USING INFORMATION TECHNOLOGY TOOLS

Abstract We present an experiment and simulations aimed at introducing the Boltzmann factor mathematical expression and at illustrating the fundamental concepts on which it is grounded. The experiment uses an easily available Microcomputer Based Laboratory apparatus. Simulations are developed in the Net-Logo environment that, besides having a friendly user-interface, allows an easy interaction with the algorithm. The approach supplies a pedagogical support for the introduction of the Boltzmann factor at undergraduate level to students without a background in statistical mechanics

KwaZulu-Natal coastal erosion events of 2006/2007 and 2011: A predictive tool?

Severe coastal erosion occurred along the KwaZulu-Natal coastline between mid-May and November 2011. Analysis of this erosion event and comparison with previous coastal erosion events in 2006/2007 offered the opportunity to extend the understanding of the time and place of coastal erosion strikes. The swells that drove the erosion hotspots of the 2011 erosion season were relatively low (significant wave heights were between 2 m and 4.5 m) but of long duration. Although swell height was important, swell-propagation direction and particularly swell duration played a dominant role in driving the 2011 erosion event. Two erosion hotspot types were noted: sandy beaches underlain by shallow bedrock and thick sandy beaches. The former are triggered by high swells (as in March 2007) and austral winter erosion events (such as in 2006, 2007 and 2011). The latter become evident later in the austral winter erosion cycle. Both types were associated with subtidal shore-normal channels seaward of megacusps, themselves linked to megarip current heads. This 2011 coastal erosion event occurred during a year in which the lunar perigee sub-harmonic cycle (a ±4.4-year cycle) peaked, a pattern which appears to have recurred on the KwaZulu-Natal coast. If this pattern proves true, severe coastal erosion may be expected in 2015. Evidence indicates that coastal erosion is driven by the lunar nodal cycle peak but that adjacent lunar perigee sub-harmonic peaks can also cause severe coastal erosion. Knowing where and when coastal erosion may occur is vital for coastal managers and planners

L’algoritmo come strumento didattico in fisica: modellizzazione dei gas ideali classici e quantistici

Viene discussa una procedura per la modellizzazione dei gas ideali quantistici. Inoltre, viene evidenziata l’importanza di supportare le incomplete rappresentazioni mentali degli studenti, in relazione ad argomenti complessi di meccanica statistica e termodinamica, con accurati modelli fisici aventi validità predittiva e fondati sull’ipotesi di possibili meccanismi di funzionamento. L’idea alla base dell’approccio proposto è quella che, in alcuni casi, anche la sola discussione dei risultati di un algoritmo o di un modello può essere sufficiente a migliorare la comprensione di un sistema fisico particolarmente complesso

Aspetti teorici e simulazioni delle statistiche quantistiche: un approccio stocastico

In questo articolo viene analizzata una procedura per la modellizzazione e simulazione di sistemi quantistici di particelle identiche non interagenti. In particolare, viene illustrato un algoritmo numerico che si dimostra in grado di prendere in considerazione gli effetti quantistici di indistinguibilità delle particelle identiche, in generale, e del Principio di Pauli per i fermioni. I risultati delle simulazioni condotte, per semplicità, su sistemi bidimensionali, permettono di rendere conto delle principali proprietà termodinamiche di diverse tipologie di sistemi (classici e quantistici) evidenziandone, al tempo stesso, analogie e differenze

Searching for the Maxwell Distribution and the Boltzmann Factor: an Inquiry-Based Approach

We report the development of a Workshop involving experimental and modelling activities aimed at facing two relevant problems currently addressed by the Physics Education Research community. These involve the organization of curricula aimed at showing the unity of physics as a subject and the ways to design affective learning environments

Collisions and mechanical wave propagation in elastic rods

Some results from experiments intended to measure the propagation speed of sound waves produced by collisions between small bodies and metallic rods are analysed. Elementary models of elastic collision and of the reflection and transmission of waves at media boundaries are discussed and tested with experimental data, in the framework of a workshop on mechanical wave propagation that featured at the University of Palermo in a two-year graduate programme for prospective physics teachers and in courses for undergraduate engineering and physics students

A PROJECT-POSED APPROACH TO REAL BODY DYNAMICS: THE ROLE OF CONSTRAINTS IN ELASTIC WAVE PROPAGATION

In this paper we present some results of a project-posed approach to the teaching of mechanical wave propagation focused on observations and measurements of wave properties in solids and on modelling of these properties by using different simulation tools. In particular, the propagation speed of sound waves in metallic rods is studied by using simple experimental arrangements based on the measurements of contact times between a small body and long metallic rods with which the body can collide. An interesting effect of this approach is the revision of students’ ideas about the rigid body model, studied at high school or college level and usually hardly followed by deepening on the fundamental role of wave propagation in the motion of real, elastic bodies. In particular, the performed experiments can stimulate students to reflect about the role of constraints in wave propagation and the general meaning of the constraint concept with respect to the dynamics of a real, elastic body. The approach has been developed in the context of a workshop on Mechanical Wave laboratory of the two-year post-graduate school for physics teacher education of University of Palermo. Some experimental results obtained by prospective teachers during lab activities and considerations about observed modifications in their attitude in utilising experiments and modelling to build pedagogical activities will be discussed