Students' conception and application of mechanical equilibrium through their sketches

This qualitative research paper describes an investigation into the reasoning and knowledge exhibited by engineering students while they sketch shear force diagrams. Sketching is an important part of engineering practice because it relies on the engineer to synthesize, organize, and communicate concepts. In this study, we investigate students’ reasoning about mechanical equilibrium as revealed through their conceptions of shear force as a material’s internal reaction to loading. This study can aid instructors as they decide how to help students understand these core concepts and engage with these sketching tasks. To understand students’ knowledge and reasoning during sketching, we conducted interviews with screen captures of the students’ sketches. Our research question in this study was how do students apply the concept of equilibrium during problem solving? We used constant comparative analysis with multiple coders to analyze the data. The theme that emerged from this study is that students believe that Equilibrium is Sum of External Forces = 0. This theme encompasses the diverse strategies students use when applying equilibrium in their sketches. A majority of the students apply equilibrium only by setting the sum of external forces to zero while solving for reaction forces. Most students fail to analyze the internal forces of the beam using “cuts” that would reveal shear force as distinct from the external forces applied to the beam.