Massimiliano Malgieri

Investigating the role of sliding friction in rolling motion: a teaching sequence based on experiments and simulations

We designed a teaching–learning sequence on rolling motion, rooted in previous research about student conceptions, and proposing an educational reconstruction strongly centred on the role of friction in different cases of rolling. A series of experiments based on video analysis is used to highlight selected key concepts and to motivate students in their exploration of the topic; and interactive simulations, which can be modified on the fly by students to model different physical situations, are used to stimulate autonomous investigation in enquiry activities. The activity sequence was designed for students on introductory physics courses and was tested with a group of student teachers. Comparisons between pre- and post-tests, and between our results and those reported in the literature, indicate that students’ understanding of rolling motion improved markedly and some typical difficulties were overcome.

Teaching quantum physics by the sum over paths approach and GeoGebra simulations

We present a research-based teaching sequence in introductory quantum physics using the Feynman sum over paths approach. Our reconstruction avoids the historical pathway, and starts by reconsidering optics from the standpoint of the quantum nature of light, analysing both traditional and modern experiments. The core of our educational path lies in the treatment of conceptual and epistemological themes, peculiar of quantum theory, based on evidence from quantum optics, such as the single photon Mach–Zehnder and Zhou–Wang–Mandel experiments. The sequence is supported by a collection of interactive simulations, realized in the open source GeoGebra environment, which we used to assist students in learning the basics of the method, and help them explore the proposed experimental situations as modeled in the sum over paths perspective. We tested our approach in the context of a post-graduate training course for pre-service physics teachers; according to the data we collected, student teachers displayed a greatly improved understanding of conceptual issues, and acquired significant abilities in using the sum over path method for problem solving.

Measuring the hydrogen Balmer series and Rydberg's constant with a homemade spectrophotometer

In a recent paper (Amrani 2014 Eur. J. Phys. 35 045001), the author presented two different methods to measure the wavelength of visible lines of Balmer series from the hydrogen atomic spectrum and estimate the value of Rydbergs constant with an error difference of a few tenths of a per cent. Here we discuss how low cost spectrometers, based on the use of either transmission or reflection diffraction gratings coupled with a commercial digital camera, can be employed with the same aim. The Rydbergs constant values obtained with our spectrometers are R = 1.096 ± 0.007 × 107 m−1 for the transmission grating spectrometer and R = 1.094 ± 0.005 × 107 m−1 for the reflection spectrometer, with a difference of less than 0.30% from the accepted value of 1.097 373 × 107 m−1.

The surprising rolling spool: experiments and theory from mechanics to phase transitions

An asymmetric rolling spool can be investigated as a simple model for a second-order phase transition. At low energy it undergoes librational motion around the equilibrium position, whereas at high energies its motion becomes rototranslational. The analysis of its dynamics shows that when approaching critical energy, the period of oscillation diverges; and this suggests the transition from one phase to the other. We thus show that the concept of ‘phase transition’, useful to describe the behaviour of a variety of thermodynamic systems, can be actualized in this simple mechanical system. Moreover, a tight analogy can be found between the rolling spool’s behaviour and the Tomlinson model of sliding friction. This analogy makes it possible to interpret the critical switch of static friction near the threshold of motion as a phase transition. The rolling spool can be easily constructed and used as a hands-on experiment. Quantitative measurements of its motion were carried out through open-source video analysis software.

The photoluminescence of a fluorescent lamp: didactic experiments on the exponential decay

The lifetimes of the photoluminescent compounds contained in the coating of fluorescent compact lamps are usually measured using specialised instruments, including pulsed lasers and/or spectrofluorometers. Here we discuss how some low cost apparatuses, based on the use of either sensors for the educational lab or commercial digital photo cameras, can be employed to the same aim. The experiments do not require that luminescent phosphors are hazardously extracted from the compact fluorescent lamp, that also contains mercury. We obtain lifetime measurements for specific fluorescent elements of the bulb coating, in good agreement with the known values. We also address the physical mechanisms on which fluorescence lamps are based in a simplified way, suitable for undergraduate students; and we discuss in detail the physics of the lamp switch-off by analysing the time dependent spectrum, measured through a commercial fiber-optic spectrometer. Since the experiment is not hazardous in any way, requires a simple setup up with instruments which are commonly found in educational labs, and focuses on the typical features of the exponential decay, it is suitable for being performed in the undergraduate laboratory.

Understanding first-year students’ curiosity and interest about physics—lessons learned from the HOPE project

This paper focuses on results of an interview based survey of first-year university physics students, carried out within the EU Horizons in Physics Education (HOPE) project (http://hopenetwork.eu/). 94 interviews conducted in 13 universities have been analyzed to investigate the factors that inspire young people to study physics. In particular, the main motivational factor, which was proven to consist of personal interest and curiosity, was unfolded into different categories and detailed interest profiles were produced. The results are arguably useful to help academic curriculum developers and teaching personnel in physics departments to provide guidance to students in developing and focusing their interest towards specific sub-fields and/or to design targeted recruitment and outreach initiatives.

Quantitative analysis of transmittance and photoluminescence using a low cost apparatus

We show how a low cost spectrometer, based on the use of inexpensive diffraction transmission gratings coupled with a commercial digital photo camera or a cellphone, can be assembled and employed to obtain quantitative spectra of different sources. In particular, we discuss its use in studying the spectra of fluorescent colored ink, used in highlighting pens, for which the transmission band and the emission peaks are measured and related to the ink color.

What are we looking at when we say magenta? Quantitative measurements of RGB and CMYK colours with a homemade spectrophotometer

We address some issues in colour theory, which are of relevance from an educational perspective. Spectra of emitted RGB and of transmitted CMYK colours are quantitatively processed and analysed with quite inexpensive homemade instruments, making use of smartphones as affordable digital cameras. LCD monitors and paper sheets with pigments coming from a laser printer are used to point out the basic differences between additive and subtractive colour formation. As an especially relevant aspect, we point out how it is possible to construct a simple model to explain the subtractive mixing process in terms of convolution of primary colour filters. The analysis presented in this work is particularly suited for enhancing the need for a proper understanding of the physiology of human eye–brain action in light acquisition and perception of colours.

Pre-service teachers' approaches to a historical problem in mechanics

In this paper we report on an activity sequence with a group of 29 pre-service physics teachers based on the reconstruction and analysis of a thought experiment that was crucial for Huygens’ derivation of the formula for the centre of oscillation of a physical pendulum. The sequence starts with student teachers approaching the historical problem and culminates in a guided inquiry activity in a video-based laboratory (VBL) setting using Tracker software. We collected data before, during and after the experimental activity by means of written questions, oral discussions and final reports. These documents provide insights into students’ initial and evolving conceptions, as well as their attitudes towards the activity. The analysis of data allows us to uncover and focus on relevant difficulties for future teachers in mastering the concepts of centre of mass and conservation of energy. Moreover, we find indications that the VBL environment makes a positive contribution by stimulating and improving students’ modelling abilities. In particular, we find a sharp increase in the percentage of students capable of producing coherent explanations and physical analyses for the Huygens’ pendulum system after the Tracker activity.

Reconstruction of Huygens' gedanken experiment and measurements based on video analysis tools

In this paper we describe the practical realization and the analysis of a thought experiment devised by Christiaan Huygens, which was pivotal in his derivation of the formula for the radius of gyration of a compound pendulum. Measurements are realized by recording the experiment with a digital camera, and using a video analysis and modelling software tool to process and extract information from the acquired videos. Using this setup, detailed quantitative comparisons between measurements and theoretical predictions can be carried out, focusing on many relevant topics in the undergraduate physics curriculum, such as the ‘radius of gyration’, conservation of energy, moment of inertia, constraint and reaction forces, and the behaviour of the centre of mass. (Some figures may appear in colour only in the online journal)