What do students learn about work in physical and virtual experiments with inclined planes?

In previous studies, we have reported a difference in how physical and virtual manipulatives support students' understanding of the physics definition of work in the context of simple machines. We have shown that students who use the virtual manipulative (a computer simulation) before performing a physical experiment provided the correct response to multiple-choice questions about work more frequently than students who first use the physical manipulative. In this paper, we further analyze students' responses to a series of questions about work in the context of inclined planes to explore the models students used to answer the questions. While we had anticipated that students who performed the physical experiment would incorrectly respond to the multiple-choice questions in accordance with their observations (i.e. a longer ramp requires more work due to frictional effects), we actually observed these students more frequently using an alternate model that a longer ramp requires less work.