This resource exemplifies the relationship between science and engineering while demonstrating how a formative assessment probe can be used to assess students' understanding. Students are asked to explain their thinking of how they might change the speed of a pendulum, launching students into a student-driven investigation to discover the variables affecting the number of swings a pendulum makes in a specific timeframe if need be. Students then apply the knowledge gained through the investigation to engage in an engineering challenge presented in the resource “Crooked Swings”.