Learning about the role of sliding friction in rolling motion: a teaching-learning sequence based on computer aided experiments and simulations.

In this work we describe the cycle of design, implementation, evaluation and redesign of a teaching learning sequence aimed at promoting students’ coherent understanding of the role of friction forces in determining the rolling motion. The sequence, designed for students of introductory physics courses and for the formation of teachers, proceeds through a combination of real experiments and interactive computer simulations, designed to sustain students’ understanding. The sequence was tested in 2014 with 20 student teachers. At the end of the first cycle of implementation we evaluated the effectiveness of the activity sequence in promoting student teachers’ reflection on basic physics contents. Data from the pre-test allowed us to identify students’ initial difficulties in understanding rolling motion and the role of friction, which broadly agree with those reported in the literature. The successes and failures of students in the post-test and final report provided relevant information in order to challenge the persistent obstacles and misunderstandings. This confirms the need of an iterative cycle of implementation, analysis and refinement of the designed sequences in order to take into account effects and elements that only a contextualized practice could reveal. In particular, analysing the results of the first experimentation, we identified one specific difficulty, namely in determining the direction of friction force in rolling motion of a body accelerated by different means, which persisted in students’ post-tests. Consequently, we worked to restructure the didactical organization of the contents and to include in the sequence new materials and activities meant to overcome the aforementioned difficulty. In order to validate our approach, in 2015 we performed second test with 19 student teachers, obtaining satisfactory results.