In this article Campbell and Neilson discuss several design strategies developed or adopted that were found particularly helpful when sequencing a unit that focused on learning about motion and acceleration. Students were expected to predict, observe, and explain why a ball traveled down one ramp faster than the other. Before engaging students,…

Examples of equilibrium are evident everywhere and the equilibrium rule provides a reasoned way to view all things, whether in static (balancing rocks, steel beams in building construction) or dynamic (airplanes, bowling balls) equilibrium. Interestingly, the equilibrium rule applies not just to objects at rest but whenever any object or system of…