Helping students relate work and changes in energy

The first law of thermodynamics states that doing work on an otherwise isolated system will cause its energy to change. Student performance in introductory mechanics on pretest and post-test questions suggests that traditional instruction is insufficient to develop a functional understanding of this principle. At the University of Washington, the Physics Education Group has been developing research-based materials\footnote{{\it Tutorials in Introductory Physics,} L.C. McDermott, P.S. Shaffer and the Physics Education Group at the University of Washington, Prentice Hall (2002).} on these topics. We will discuss common student difficulties in applying the relationship between work and energy, and implications these have for instruction on energy conservation.