How simplifying problems does not simplify learning

LAURA BUTELER; ENRIQUE COLEONI

San Pablo

Congreso; 2nd World Conference on Physics Education; 2016

IUPAP-GIREP-USP

Providing simplified problems is common practice in instructional settings for physics teaching. Numerous examples supportthis statement. From idealized pointmassesmoving at constant speed in straight lines, to circuits consisting of ideal nonresistantwires and pure resistances, to completely rigid surfaces that can exert different contact forces on the bodies layingagainst them. Reasons to use simplified situations are compelling: they allow putting students in situations that, it isassumed, are physically and mathematically affordable for them to address. Among such problems, we can find those used ininstructional settings to teach the concept of buoyancy. In general, these problems consist of ideal bodies either floating orsubmerged in different fluids (typically water). In the case of bodies submerged at the bottom of a fluidfilledcontainer,problems call for the recognition, besides the body´s weight, of two different upward forces on the body: buoyancy and anormal contact force from the container surface. As we will show through the data collected, the implicit idealization of thebody´s and container´s surfaces, leads the university students in our study to struggle with nontrivialphysical implicationsclosely linked to the concept of buoyancy. Students´ struggle can be synthesized in the question ?how is the contact betweenbody and container so that both buoyancy and a normal contact force can exist at the same time?? Journals like The PhysicsTeacher and Physics Education have shown the debate that experts (teachers) have carried out on the nuances of theconcept of buoyancy in such cases. In the present work, the issue is approached from the perspective of students, that is,from the perspective of those who are making an effort to learn. In order to do so, Coordination Class Theory is adopted. Theattention is therefore focused on students rather than teachers. Results show how, in order to understand how buoyancy actsin this particular context, students need to recover the real complexity of the problem that was lost in its simplified version.Their query, one of profound conceptual implications, is responded when they address the analysis of the contacting surfacesat a microscopic level. This contact surface had been implicitly transformed into a smooth contact between two ideally flatsurfaces in the process of simplification.