2023 ASEE Annual Conference & Exposition

Students often practice drawing free body diagrams (FBDs) for abstract, text-book style problems where extraneous details in the problem description and accompanying figures have been removed. Since practicing engineers often need to draw FBDs in more realistic contexts, an important question is: can students draw FBDs as well when faced with a less abstract problem representation? Anecdotal information collected by several instructors suggest that decreased levels of abstraction in problem depiction (i.e., greater realism) lead to decreased student performance.

To explore this question, students were asked to draw FBDs for problems with figures at different levels of abstraction: high abstraction (geometric shapes only), medium abstraction (line drawings of objects - like most textbook problems), and low abstraction (photographs of objects). Students in a first-year course, who had just learned to draw FBDs, and students in a third-year course, who were experienced with FBDs, were surveyed. As hypothesized, student performance decreased with decreased abstraction (i.e., greater realism), but this was only the case for first-year students. These results suggest that care should be taken in choosing the level of abstraction for problem representations used for FBD instruction. Students just learning to draw FBDs may be helped by highly abstract problem representations so that these problems are easier. But having more experienced students wrestle with less abstract scenarios when drawing FBDs may help them prepare to draw FBDs in the real world. The detailed results also suggest that instruction focused on helping students to isolate bodies in more realistic or hands-on environments may be warranted for all students of mechanics.