Instrument for Assessing Skills related to Free Body Diagrams in a Sophomore Engineering Mechanics Course
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American Society for Engineering Education, 2017. Commonly, engineering faculty members who teach a sophomore engineering mechanics course find that the ability of students to idealize a mechanical system and draw its free body diagram (FBD) is a threshold concept that once mastered can change the way a student progresses through the discipline. While there are inventories available related to engineering mechanics, there is not one solely focused on the intricacies of FBDs of mechanical systems and the inclusion of all independent constraint forces and moments, a crucial skill in engineering. The goal of this study is to develop and validate an instrument for FBDs containing both free response and multiple-choice questions. The objectives in this study include the ability of a student to: properly identify and isolate the system; account for correct constraint forces and moments; utilize Newton's third law; indicate external and internal forces; apply friction when appropriate; identify bodies in motion properly; designate cables, normal forces, and two force members correctly; and specify the effect of gravity correctly. The instrument developed as part of this study was administered to a set of students taking a typical sophomore mechanics course at a large public institution during fall 2016, along with a smaller group of students used in a pilot study during spring 2016. The paper will describe: 1) details on the alpha and beta versions of the FBD instrument developed; 2) early lessons learned; and 3) results from approximately 250 engineering students who took the beta version of the instrument. After administering the instrument and analyzing the results, faculty members have a better idea of the skill set of students in the course and can adjust course instruction appropriately. Furthermore, there will be evidence to examine the extent to which students are prepared related to free body diagrams at the end of a core engineering science course.
