Student Thinking about Static Equilibrium: Insights from Written Explanations to a Concept Question

Students' thinking during an assessment task was monitored by analyzing their explanations of answers to a multiple‐choice question about the equilibrium of bodies under given loads. Based on coding by independent raters, we found that nearly all students explained answers by appealing to force and/or moment summation; they differed principally on whether they applied both force and moment equilibrium and did so consistently. Correlations between answer selection and explanation as found from coding suggested that a reasonable guess as to a student's thinking can be made based on the answer choice alone. By the final exam, some students improved in their ability to consistently apply both principles or at least to apply them when needed. Many other students apparently learned to apply one of the principles consistently, although they came to ignore the other principle, even if they had acknowledged it at the start of the course.