Comparison of evaluation strategies in physics problem solving between first- and third-year students.

One expected student outcome of physics instruction is a set of quantitative reasoning skills that include evaluation of problem solutions. As part of a larger project, we developed and administered tasks to physics students that probe their use of these kinds of evaluation strategies. In a pair interview setting, we asked first-year students and juniors to evaluate expressions for the final velocities of two skaters involved in a one-dimensional elastic collision. The techniques used by the two groups show the differences between novice and intermediate versions of certain evaluation strategies. To do this, we focus on the role of algebra and mathematical operations in the checking process, how the students seem to view equations, and the different ways numbers are plugged into the given equations. We observed a few characteristic differences between the groups which showed an evolution in strategy implementation. For instance, the first-year students plugged exact numbers into the given expression (e.g., m₁=2kg, m₂=5kg) while the juniors plugged in ratios of numbers (e.g., m₁=100m₂). Other differences include the way knowledge of physics is used, how students seem to view equations, and the role of algebra and mathematical operations while evaluating the given expression.