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A study of the Efficacy of Free-body Diagrams for the Solution of Frame-Type Mechanics Problems with Increasing Difficulty Level

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2019 ASEE Annual Conference & Exposition


Tampa, Florida

Publication Date

June 15, 2019

Start Date

June 15, 2019

End Date

June 19, 2019

Conference Session

Mechanics Division Technical Session 6

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Paper Authors


Jeffrey A. Davis Grant MacEwan University

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Dr Davis obtained his PhD at ETH Zurich specializing in multiphase flows and thermal hydraulics in nuclear reactors. With a passion for teaching, Dr. Davis' research focuses on pedagogical topics such as student engagement, active learning, and cognitive development. Projects he is currently working on include “Development of a risk assessment model for the retention of students”, “Development of Student Assessment Software”, and “Improving Student Engagement through Active Learning”.

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Shelley Lorimer Grant MacEwan University

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Shelley Lorimer is an Associate Professor in Engineering (BSEN) Transfer Program at Grant MacEwan University. She is an instructor in the introductory engineering courses as well. The BSEN program at MacEwan has grown from forty students since in started more than twenty years ago, to the current 216 students. The majority of the students in the program transfer to second year engineering at the University of Alberta.

Shelley is a graduate of the University of Alberta in engineering and is a registered professional engineer with APEGA (Association of Professional Engineers, Geologists and Geophysicists of Alberta). Prior to her career at MacEwan, Shelley worked in industry as a research engineer and a consulting engineer for several years.

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Free-body diagrams are commonly used by engineers and physicists as a visual aid in the solution process of many mechanics problems, both simple and complex. In a typical first-year engineering mechanics course, free-body diagrams are used for a variety of problems in particle and rigid body equilibrium including: trusses, frames and machines, friction and wedges, and internal forces in structures. Although the underlying physics behind each problem type is the same (governed by the equations ∑F=0 and ∑M=0) these topics have evolved into separate teaching modules in a typical first-year engineering statics curriculum due to their distinct conceptual complexities. A review of the literature indicates that research to date has focused on the use of free-body diagrams in only a few of the first-year topics (particle and rigid body equilibrium, electrostatics, and friction). At present the effect of the use of free-body diagrams in the problem solving process for frame and machine type of problems has gone unstudied. This research uses an evidence-based approach to study the impact that free-body diagrams have on solutions developed by first-year engineering students in a statics course. Using final exams from a first-year statics course, the effectiveness of using free-body diagrams on the problem-solving process for frames and machines type problems was analyzed for two independent cohorts of engineering students in two different years. The specific problems considered were frame type problems which included multiple members (including a two-force member) and different distributed loading configurations of varying difficulty. The free-body diagrams and the resulting equations were evaluated by assessing the accuracy and quality of the drawings using a rubric designed by the researchers. The data collected for the study was then analyzed using statistical methods and the results are discussed with respect to: identifying the common mistakes that students make on frame type problems, quantifying the mistakes that students make when including moment equations, tabulating the common errors made when including two force members, and determining the effect of increasing difficulty level in frame type problems. Results indicate that free-body diagrams become more important for the development of correct equations of a frame and machine type problem as the complexity of the problem increases.

Davis, J. A., & Lorimer, S. (2019, June), A study of the Efficacy of Free-body Diagrams for the Solution of Frame-Type Mechanics Problems with Increasing Difficulty Level Paper presented at 2019 ASEE Annual Conference & Exposition , Tampa, Florida. 10.18260/1-2--32003

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