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Free Body Diagrams: How Do We Know if Students Benefit from Using Them?*

Free Body Diagrams: How Do We Know if Students Benefit from Using Them?*. David Rosengrant, Eugenia Etkina, Alan Van Heuvelen Rutgers, The State University of New Jersey PERC 2006, Syracuse, New York. * Supported in part by NSF grants DUE 0241078, DUE 0336713. Motivation for this Study.

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Free Body Diagrams: How Do We Know if Students Benefit from Using Them?*

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  1. Free Body Diagrams: How Do We Know if Students Benefit from Using Them?* David Rosengrant, Eugenia Etkina, Alan Van Heuvelen Rutgers, The State University of New Jersey PERC 2006, Syracuse, New York * Supported in part by NSF grants DUE 0241078, DUE 0336713

  2. Motivation for this Study • Students solve problems like novices. • Real life problems are incompatible with the “Plug and Chug” problem solving mentality. • We want students to solve problems like experts. • Experts use multiple representations when solving problems. • We teach students to use multiple representations to solve problems. • Do students actually use them while solving problems, and if they do, then how do the representations help them?

  3. Research Questions If we create an environment where the instructor models the use of free-body diagrams (FBDs) in problem solving, then . . . 1. Do students use FBDs on their own in solving problems? 2. Are those who use FBDs more successful in solving problems? 3. How do students use FBDs to help them solve problems? 4. What are possible relationships between the type of problem and how likely students will draw an FBD for it?

  4. Course Format • Algebra-based Physics course, 500 students/year. • Two 55-min large-room meetings, one 55-min recitation and one 3-h laboratory per week. • Used Investigative Science Learning Environment ISLE (Etkina & Van Heuvelen, 2001). • Inquiry-based learning system • ISLE emphasizes MULTIPLE REPRESENTATIONS and incorporates them in concept construction and problem solving • Active Learning Guide • Model solutions for the homework • Multiple Representation tasks in Recitation

  5. Free body diagrams (FBD) You are riding to the top floor of your residence hall. As the elevator approaches your floor, it slows to a stop. Construct an FBD for the cable car [with you inside] as the object of interest as the car slows down to a stop. Cable Earth

  6. Sample and Data SourcesQuantitative Study • Sample • 125 Students randomly selected (25%) Year 1 • 120 Students randomly selected (29%) Year 2 • Source • 2 Midterms, 1 Final per semester • 5 Multiple-choice problems Year 1 • 7 Multiple-choice problems Year 2 • no credit for diagrams!

  7. If we teach students to solve problems using FBDs, do they use FBDs to solve problems?

  8. If we teach students to solve problems using FBDs, do they use FBDs to solve problems?

  9. Coding Scheme

  10. Are those who use FBD’s more successful? 58% 14/24 31% 4/13 58% 26/45 93% 40/43 67% 84/125

  11. Are those who use FBD’s more successful? Second year is similar to the first year. 60% 885/1465 71% 261/370 85% 251/295 38% 69/181 49% 304/619

  12. Is the relationship between student success rate and the quality of their FBDs significant? * Statistically significant at alpha of 0.05, t ≥ 2.201 ** Statistically significant at alpha of 0.01, t ≥ 3.106 I used a two-sample t-test for independent samples based on separate variance estimates because one person may be in multiple categories (Abrami, Cholmsky, and Gordon, 2001)

  13. Sample-Case Study High Achieving Student Low Achieving Student Used Many MRs Anna Jose Used Few MRs Mary Eileen Students with a Different Instructor Sahana Krutick

  14. Data SourcesQualitative Study • Source – 2 Interviews • Interview 1 • One on One – 2 Open Ended problems for students to solve • Interview 2 • Reviewed previous exam problems and talked about their problem solving strategy.

  15. How do students use free-body diagrams when solving problems?

  16. What are possible relationships between the type of problem and how likely students will draw an FBD for it?

  17. Summary of Findings • If we teach students to solve problems using FBDs, do they use FBDs to solve problems? • YES • 846 problems (58%) with • 619 problems (42%) without 42% w/o 58% With

  18. Summary of Findings • Are those who use FBD’s more successful? • YES – Average success rate of all 12 questions: • Score of a 3 85% Score of a 2 71% • Score of a 1 38% Score of a 0 49% • Success Rate 60%

  19. Summary of Findings • Why do students use free-body diagrams to help them solve problems? • High achieving students used representations to • clarify problem situation • evaluate other representations • evaluate the answer • Low achieving students used them because their instructor used them. • What are possible relationships between the type of problem and how likely a student will draw an FBD for it? • We found 2 key factors • Positive - Problem asks for a magnitude of force • Negative - Pictorial representation of the problem situation is provided to the students

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