This paper describes the design and development of a set of teaching materials for the teaching of a topic on mechanics (as part of the research carried out for the 'Conceptual Change in Science' project). The 'curriculum' comprises a series of interactive computer simulations of force and motion, a number of closely related practical activities and associated written materials. The aim of the materials was to promote change in learners' understandings of physical phenomena, by first making them aware of the limitations of their current conceptions, and then by enabling learners to develop and use a conceptual framework which both fits with their experience and is internally consistent.