Improving understanding of reaction forces in free body diagrams using a paired vector object in Prairie Learn

Hadas Ritz; Sanjit Basker; JINGJIE YEO

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Conference: 2022 ASEE Annual Conference & Exposition
Location: Minneapolis, MN
Publication Date: August 23, 2022
Start Date: June 26, 2022
End Date: June 29, 2022
Conference Session: Statics Fanatics 2
Page Count: 13
DOI: 10.18260/1-2--41583
Permanent URL: https://peer.asee.org/41583
Download Count: 442

Paper Authors

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Hadas Ritz Cornell University

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Hadas Ritz is a senior lecturer in Mechanical and Aerospace Engineering, and a Faculty Teaching Fellow at the James McCormick Family Teaching Excellence Institute (MTEI) at Cornell University, where she received her PhD in Mechanical Engineering in 2008. She received the 2021 ASEE National Outstanding Teaching Award.

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Sanjit Basker

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Sanjit is an engineering student at Cornell. His interests lie in aerospace propulsion and machine learning.

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JINGJIE YEO Cornell University

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Prof. Jingjie Yeo is the Principal Investigator at the J² Lab for Engineering Living Materials. The Lab performs Computations in Materials and the Sciences to engineer dynamically-responsive, living materials through interdisciplinary studies of material and biological phenomena with multiscale computational methods for engineering and medical applications. He is a co-instructor in Station1, a social nonprofit organization dedicated to building the foundations of the university of the future through educational opportunity and socially-directed frontier STEM education, research, and internships. Before joining Cornell University in 2020, Prof. Yeo was a research scientist in the Institute of High Performance Computing, Singapore. He worked on developing cutting-edge, silk-based cosmeceuticals and also collaborated closely with Procter & Gamble for molecular dynamics (MD) modeling of keratins and pigment cells. Prior, he was a postdoc at both Tufts University and Massachusetts Institute of Technology, where he developed and performed numerous multiscale simulations with density functional theory (DFT) and fully-atomistic to coarse-grained MD modeling on a broad variety of biomaterials such as squid skin, silk and silk-elastin-like proteins, and graphene. He received his Ph.D. and his B.Eng. degrees from Nanyang Technological University Singapore.

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Abstract

A foundational skill in mechanics is the ability to draw complete and correct free body diagrams (FBDs). Students benefit from extensive practice and feedback as they build their FBD skills, but in large enrollment courses the ability for course staff to give detailed individual feedback is limited. That mismatch between need for feedback and capacity to provide it drives adoption of teaching software with automated grading, such as PrairieLearn (PL). In the sophomore level Statics and Mechanics of Solids course at Cornell University we have recently introduced limited use of PL to give students additional practice with FBDs.

One particularly challenging application of FBDs for new learners in a statics course is for "frames" or "mechanisms." These consist of multiple members, both two-force and multiforce members, pinned together and loaded with forces and/or moments at any location. A major point of confusion for students in the course is how to treat reactions on members separated from each other at pins, including identifying two-force members and correctly showing equal and opposite reactions on the separated members. When we began using PL for our course, there was no mechanism in that platform to grade "exploded" FBDs for frames, which significantly limited the utility of the platform for our students. We hypothesized that students would perform better when drawing FBDs by hand outside of the PL platform if they could practice placement of two vectors in PL as the equal and opposite reactions where members are separated from each other. To test this hypothesis, we devised and implemented a new object in PL, a "paired vector" object, that allows students to practice drawing exploded FBDs and simultaneously reinforces the concept of equal and opposite reactions. We then randomly divided the 240 person course into two groups. Each group had two PL assignments during the statics unit of the course. The first assignment was identical for all students, but for the second one, the intervention group had frames problems including the paired vector object and exploded FBDs, while the control group had modified versions of the same problems that did not involve drawing equal and opposite reactions. On one midterm exam and the final exam we included problems requiring exploded FBDs. We compare performance on drawing FBDs, including frequency of specific mistakes, between the intervention and control groups. Our results suggest that practicing with the paired vector object led to better outcomes on drawing exploded FBDs and decreased the incidence of incorrect reactions at joints where members are separated from each other.

Citation
Format

Ritz, H., & Basker, S., & YEO, J. (2022, August), Improving understanding of reaction forces in free body diagrams using a paired vector object in Prairie Learn Paper presented at 2022 ASEE Annual Conference & Exposition, Minneapolis, MN. 10.18260/1-2--41583

TY - CPAPER
AB - A foundational skill in mechanics is the ability to draw complete and correct free body diagrams (FBDs). Students benefit from extensive practice and feedback as they build their FBD skills, but in large enrollment courses the ability for course staff to give detailed individual feedback is limited. That mismatch between need for feedback and capacity to provide it drives adoption of teaching software with automated grading, such as PrairieLearn (PL). In the sophomore level Statics and Mechanics of Solids course at Cornell University we have recently introduced limited use of PL to give students additional practice with FBDs.

One particularly challenging application of FBDs for new learners in a statics course is for "frames" or "mechanisms." These consist of multiple members, both two-force and multiforce members, pinned together and loaded with forces and/or moments at any location. A major point of confusion for students in the course is how to treat reactions on members separated from each other at pins, including identifying two-force members and correctly showing equal and opposite reactions on the separated members.
When we began using PL for our course, there was no mechanism in that platform to grade "exploded" FBDs for frames, which significantly limited the utility of the platform for our students.

We hypothesized that students would perform better when drawing FBDs by hand outside of the PL platform if they could practice placement of two vectors in PL as the equal and opposite reactions where members are separated from each other. To test this hypothesis, we devised and implemented a new object in PL, a "paired vector" object, that allows students to practice drawing exploded FBDs and simultaneously reinforces the concept of equal and opposite reactions. We then randomly divided the 240 person course into two groups. Each group had two PL assignments during the statics unit of the course. The first assignment was identical for all students, but for the second one, the intervention group had frames problems including the paired vector object and exploded FBDs, while the control group had modified versions of the same problems that did not involve drawing equal and opposite reactions. On one midterm exam and the final exam we included problems requiring exploded FBDs. We compare performance on drawing FBDs, including frequency of specific mistakes, between the intervention and control groups. Our results suggest that practicing with the paired vector object led to better outcomes on drawing exploded FBDs and decreased the incidence of incorrect reactions at joints where members are separated from each other.

AU - Hadas Ritz
AU - Sanjit Basker
AU - JINGJIE YEO
CY - Minneapolis, MN
DA - 2022/08/23
PB - ASEE Conferences
TI - Improving understanding of reaction forces in free body diagrams using a paired vector object in Prairie Learn
UR - https://peer.asee.org/41583
DO - 10.18260/1-2--41583
ER -