Enhancing understanding of conceptual relationships in introductory mechanics
For more than four decades researchers in the field of introductory mechanics have investigated ways to develop student understanding of physics concepts and overcome deficiencies in student ability to apply physics knowledge in everyday contexts. However, a core research problem that remains is that only limited success has been obtained in addressing the difficulties students experience when learning classical mechanics, especially with regard to acceleration and free-fall motion. The large body of literature confirms that conceptions arising from student everyday experiences and the ways they seek to make sense of these experiences contribute to many conceptual difficulties. The research reported in this thesis is motivated by the desire to improve specific aspects of the teaching of some core concepts and relationships in introductory mechanics, with particular focus on motion under gravity and net force-mass-acceleration relationship expressed in Newton’s second law. The research has focused on circumstances which could potentially enhance understanding of conceptual relationships and concepts for motion under gravity. The circumstances investigated were: • Considering the impact of a simplification of physics per se • Using multiple representations • Qualitative (proportional) reasoning / using equations as reasoning tools • A qualitative approach to teaching acceleration The research has followed a Design-Based Research approach. This methodology was chosen for its use of iterative cycles of design and evaluation of solutions to practical problems. The different iterations of the study, some qualitative and some quantitative, were conducted with different research groups of physics learners, as individual investigations. The results of the iterations indicate that attention to the four circumstances mentioned above, as applied in the research, did in fact enhance student understanding of the concepts and conceptual relationships of motion under gravity. Two outcomes of the research have specific value beyond this study, namely a qualitative approach to teaching acceleration as the net force to mass ratio and a graphical tool to help students understand the effect of air resistance on falling objects and the concept of free fall. In addition to these outcomes, a set of design principles is presented which can inform the design of topic specific teaching interventions.