A constructivist model for physics instruction is developed adapting ideas from recent overseas work in physics educational research. Based on this model, small group collaborative problem solving activities were introduced into PHYS102 tutorials at the Department of Physics and Astronomy at the University of Canterbury in 1998. Students were given a prescribed problem solving strategy, and a formal process for groupwork. Observations and data gathered from recordings of students working in small groups were used to evaluate these changes. Well functioning collaborative groups were found to assist in developing concepts and understanding, particularly through student discussion that has been called 'second teaching', an idea which is interpreted using theory from Lev Vygotsky. Collaborative problem solving with wellfunctioning small groups can often produce better quality solutions than from individuals on their own. The role of 'monitor' or 'critic' was found to be essential for high-performing groups. Such groups do not happen automatically, and the role of tutors in helping establish and manage a collaborative environment is crucial. Student feedback, gained from questionnaires and follow-up interviews, was positive. There are differences between the culture of this country and that of overseas where the original research was conducted. This has lead to recommendations that for implementing groupwork in this country, tutor training be improved, and that each tutor group be involved initially in refining and adapting a shared understanding of group work and problem solving.