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.