Aspects multiples dans l'élaboration et l'expérimentation d'une séquence d'enseignement sur le frottement : analyse historique du contenu, parcours conceptuels, modèles explicatifs, formation des enseignants.

The elaboration of a teaching learning sequence on a specific topic is a complex process involving various aspects. We have developed a process of construction and evaluation of a sequence on friction, based on a preliminary study involving: critical and historical analysis of the scientific content, analysis of didactic research on the topic and of the usual teaching approaches. We formulated three hypotheses: the early proposition of a wide range of phenomena and experiments favors a more critical and wider view on the topic (H1); the use of physical structural models, involving intuition and images, helps students to overcome common difficulties and build mental models of friction mechanisms (H2); cognitive motivation of teachers in necessary to produce a change of traditional presentations (H3). To favor the reproducibility in a school real context, the sequence is designed as an “open source structure”, with a core of contents, conceptual correlations and methodological choices, and a cloud of elements that can be re-designed by teachers. The sequence has been tested in teacher initial education and in Italian high school with positive results in overcoming typical students’ difficulties and in activating new richer reasoning. Hypotheses H1 and H2 appear to be well supported and positive elements have emerged on the effectiveness of the “open source structure” of the project.