353 research outputs found
Calculating and Understanding: Formal Models and Causal Explanations in Science, Common Reasoning and Physics Teaching
No full textThis paper presents an analysis of the different types of reasoning and physical explanation used in science, common thought, and physics teaching. It then reflects on the learning difficulties connected with these various approaches, and suggests some possible didactic strategies. Although causal reasoning occurs very frequently in common thought and daily life, it has long been the subject of debate and criticism among philosophers and scientists. In this paper, I begin by providing a description of some general tendencies of common reasoning that have been identified by didactic research. Thereafter, I briefly discuss the role of causality in science, as well as some different types of explanation employed in the field of physics. I then present some results of a study examining the causal reasoning used by students in solid and fluid mechanics. The differences found between the types of reasoning typical of common thought and those usually proposed during instruction can create learning difficulties and impede student motivation. Many students do not seem satisfied by the mere application of formal laws and functional relations. Instead, they express the need for a causal explanation, a mechanism that allows them to understand how a state of affairs has come about. I discuss few didactic strategies aimed at overcoming these problems, and describe, in general terms, two examples of mechanics teaching sequences which were developed and tested in different contexts. The paper ends with a reflection on the possible role to be played in physics learning by intuitive and imaginative thought, and the use of simple explanatory models based on physical analogies and causal mechanisms
Cooling and warming laws: an exact analytical solution
No full textThis paper deals with temperature variations over time of objects placed in a constant-temperature environment in presence of thermal radiation. After a historical introduction, the paper discusses the cooling and warming laws, by taking into account first solely object-environment energy exchange by thermal radiation, and then adding object-environment heat exchange by convection. These processes are usually evaluated by approximating the law of exchange of thermal radiation by a linear relationship between power exchange and temperature difference. On the contrary, in this paper an exact analytical solution considering Stefan’s fourth power law is provided, under some general hypotheses, for both cases. A comparison with exponential approximations and with a historical law proposed by Dulong & Petit in 1817 is presented. Data of an experiment are used to test the analytical solution: the test has allowed evaluating the heat transfer coefficient h of the experiment and has shown that our solution provides a better fit with measured values than any exponential function. The topic is developed in a way which can be suitable both for undergraduate student and general physicist
Some features of causal reasoning: common sense and physics teaching
No full textThe idea of causality is central in science and has long given rise to debate among philosophers and scientists. While the tendency to avoid causality seems to have become dominant in science and philosophy, research in science education has shown the strong presence in common reasoning of causal explanations, often conceived as a 'mechanism' capable of accounting for physical transformations. Some researchers have proposed using this common causal reasoning as a basis for teaching-learning sequences, especially in electricity and mechanics. This paper analyses some features of causal reasoning used in physics by students, using questionnaires and interviews involving students and teachers. This study has shown three aspects which are related to one another: a confusion between efficient and contingent causes, between the conditions of occurrence of a phenomenon and the cause actually producing it; a tendency to 'displace' causes, skipping intermediate objects; and a difficulty in connecting local causes and global effects. The paper highlights the differences between common reasoning and scientific usage, and their effect on learning. In fact, these trends of reasoning must be taken into account in teaching: they should be considered not only as creating an obstacle to learning physics, but also as resources at the learner's disposal
The cooling law and the search for a good temperature scale, from Newton to Dalton
No full textThe research on the cooling law has begun with a Newton’s article published in 1701. Later, many studies were performed by other scientists confirming or confuting Newton’s law. The present paper presents a description and an interpretation of the Newton’s article, provides a short overview of the research on the topic performed during the 18th century, and discusses the relationships between the research on cooling laws and the definition of a temperature scale, as it was treated in the Newton’s article and in the work of Dalton, including the Dalton’s search for the absolute zero of temperature. It is shown that these scientists considered the exponential cooling law as a fundamental principle rather than a conjecture to be tested by means of experiments. The faith in the simplicity of natural laws and the spontaneous idea of proportionality between cause and effect seem to have strongly influenced Newton and Dalton. The topic is developed in a way which can be suitable both for undergraduate student and general physicist
Historical Scientific Models and Theories as Resources for Learning and Teaching: The Case of Friction.
No full textThis paper presents a history of research and theories on sliding friction between solids. This history is divided into four phases: from Leonardo da Vinci to Coulomb and the establishment of classical laws of friction; the theories of lubrication and the Tomlinson’s theory of friction (1850–1930); the theories of wear, the Bowden and Tabor’s synthesis and the birth of Tribology (1930–1980); nanotribology, friction at the atomic scale, and new fields of research (after 1980). Attention is given to recent research, so giving the sense of a topic that is still alive and currently an object of interest, with interpretative controversies. The development of explanatory and visual models is especially
stressed, in connection with students’ common ideas and with didactic purposes. The history shows that many models proposed in the past have been modified but not abandoned, so that here the scientific evolution has worked more by adding than by eliminating. The last sections discuss problems and proposals on teaching friction and the possible uses in teaching of models, images and theories found in history. Concerning the role of the
history in science teaching, the case of friction has particular features, because some recent developments are unknown to most teachers and many results, also not very recent, contrast with the laws usually proposed in textbooks. Here history can supply a number of models, examples and experiments which can constitute useful resources to improve student understanding, joining together objectives of cultural value and of better scientific
knowledge
Du frottement à la tribologie : survol historique.
No full textThe article proposes a short history of the research on friction. For every period, the most important themes and results are outlined: the early laws and theories on friction from Leonardo to Amontons and Coulomb; the theory of lubrication and the models of rolling friction, from 1840 to 1930; the theories of wear, the synthesis of Bowden and Tabor and the birth of tribology; the recent developments, with the new scientific instruments and the study of friction at the atomic scale, the nanotribology. Some didactic reflections introduce and conclude the article
Students' conceptions of fluids
No full textThis article describes a research study concerning students’ conceptions and reasonings about fluids and pressure in static situations. After a preliminary survey involving interviews and observations in class, some written questions were answered by various groups, totalling 428 Italian and French pupils in upper secondary school, 458 first-year university students in Belgium and 58 teachers-in-training. After briefly illustrating some results
from previous research on this topic, the article introduces the guidelines and objectives of the current research, describes and discusses its results, highlighting some categories of the more diffuse conceptions and tendencies of reasoning, and supplies a few suggestions for teaching. It is shown, among other things, that the notion of hydrostatic pressure is strongly connected to the idea of weight and associated with all the ambiguities that
usually go with the latter. Moreover, a critical point appears to be the difficulty in connecting local actions and global effects, the need for systemic reasonings that are capable of producing the mechanism with which to establish a situation of equilibrium
The history of cooling law: when the search for simplicity can be an obstacle
No full textThis paper presents an historical overview of the research on the cooling law, from Newton until the beginning of 20th century, and provides some suggestions for the use of this history as a resource for teaching. This history begins with a description and an interpretation of Newton’s earlier works in 1701 and an overview of studies confirming or confuting Newton’s law during the 18th century. Subsequently, it presents the early studies on cooling due to radiant heat, the fundamental work of Dulong & Petit published in 1817, and a brief overview of the research conducted after 1850 on the laws of thermal radiation and of natural and forced convection. It is shown that many scientists persisted in maintaining Newton’s law, despite numerous evidence to the contrary, by attributing the found discrepancies to empirical errors or to other disturbance factors. Many scientists considered this law as a fundamental principle rather than a conjecture to be tested by means of experiments, while others were searching for a different but general and unique cooling law. The faith in the simplicity of natural laws and the spontaneous idea of proportionality between cause and effect seem to have strongly influenced Newton and many later scientists. A discussion of epistemological, methodological and pedagogical implications is offered
Work and Energy in the Presence of Friction: The Need for a Mesoscopic Analysis
No full textThis paper deals with some of the difficulties involved in correctly linking the mechanical and thermodynamic descriptions of situations where there are bodies in motion and changes in temperature and/or heat exchanges. It proposes and discusses a definition of internal energy and shows that the total work of the non-conservative forces, such as frictional forces, always equals zero. The energy balances of two bodies in motion in the presence of sliding friction are analysed in this way; the calculation of the work of frictional forces is discussed, taking into account the mesoscopic level
Do things weigh more or less in the mountains?
No full textThe notion of weight can be associated with three distinct physical quantities: the force of gravity due to the Earth; the resultant of this gravitational force and the centrifugal force arising from the Earth’s rotation; and the ‘apparent weight in air’, i.e., what is measured by a scale located in the Earth’s atmosphere. Starting from a real life student–teacher exchange, this article sets out the variety of meanings that students and teachers may attribute to the term ‘weight’. It then explores how the weight and apparent weight of an object vary with mountain altitude. The effects of the mass of the mountain and the buoyant force of the air are considered and calculated. The question of whether apparent weight increases or decreases with increasing elevation
is addressed in detail
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