This article reports on results of an exploratory study on undergraduate pre-service teachers' understanding of graphical representations of motion functions. The study described pre-service teachers' explorations using a CBR device. Pre-service teachers' growth was studied in two dimensions: (a) in their learning of the mathematics involved and (b) in their learning of the pedagogy related to the mathematics and the technology used. Through their interaction with the device, pre-service teachers were able to overcome common misconceptions with respect to the mathematics and also to develop pedagogical insights regarding the teaching of the concepts. (Contains 1 table and 3 figures.)