Conceptual representation of the Newtonian model of motion in university physics students

The purpose of this study was to investigate how undergraduate students at the University of Northern Iowa who had taken prior coursework on non-calculus general physics with a unit on mechanics understand the Newtonian model of motion. In general, the study was concerned with reasoning strategies, the preconceptions that give rise to these strategies, and the schema that might be inferred from the preconceptions. In particular, the study focused on the three fundamental notions of the Newtonian model of motion: {a) that uniform straight line motion is equivalent to rest, {b) that motion is relative to an inertial frame of reference including that of the earth if the acceleration due to rotation of the latter is neglected, and {c) that uniform straight line motion can exist in the absence of a net force. Paper and pencil tasks in an interview mode were employed throughout the study. However, a short clinical interview was also used in order to assess prior knowledge of the above notions. The tasks were designed according to the Phenomenographic approach to investigating different understandings of reality, and the Rule Assessment Methodology in order for a variety of strategies, correct or incorrect, that a student might think of, be identified. It was found that for the great majority of students uniform straight line motion is viewed as being fundamentally different from the state of rest, and that uniform straight line motion can exist only in the presence of a net force. As for the notion of relativity, students adopt a point of observation, rather than an inertial frame of reference, and motion is viewed relative to that point. This point was either on the ground or on the fixed stars depending upon the context of the problem in question. Several preconceptions and two types of schemata were also identified. In regard to the implications of the findings of the study for instructional practices, the explicit teaching of the Newtonian model as well as the provision of advance organizers and schemata at an early age should be given priority by physics instructors