This paper describes a development project carried out in 2008/9 aimed at developing model-based learning in mechanics for a first year physics module. Based on the work in the literature VPython the visual extension to the Python programming language was chosen as the vehicle for developing the models. VPython is ideally suited to modelling mechanics for various reasons including a class of variables called vectors which have all the properties of vectors in mathematics the ease with which basic models in VPython can be constructed and the instant feedback on the operation of the models afforded by their visual nature. Thus the emphasis is much more on the physics and the modelling rather than computation. It is shown how an analysis of students‟ understanding has revealed that Newton‟s third law of motion causes difficulties leading to a greater emphasis on this concept in the modelling for 2009/10. In addition a greater attention was given to the methods and techniques of modelling especially spatial reasoning. The evidence for student reasoning in this way is presented.
