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A PEN-BASED STATICS TUTORING SYSTEM Jack Lee Thomas Stahovich Robert Calfee Presented by: James Herold Demo Outline • Introduction • Solving a problem • System Boundaries • Drawing/Critiquing Forces • Writing/Critiquing Equations • User Study • Results • Conclusion Textbook instructions for FBDs • Step 1: Decide what system to isolate. • Step 2: Next isolate the chosen system by drawing a diagram which represents its complete external boundary. • Step 3: Identify all forces which act on the isolated system… -- J.L. Meriam and L.G. Kraige. Engineering Mechanics - Statics. John Wiley & Sons, Inc., 6th edition, 2007. Typical Student Work Typical Student Work Solving a problem Create Boundary Draw Forces Write Equations Critique Boundary Critique Forces Critique Equations Done!! Creating a Boundary Critiquing Boundary: Statically indeterminate Critiquing Boundary: Cutting through rigid bodies Critiquing Boundary: Does not contain the force of interest Solving a problem Create Boundary Draw Forces Write Equations Critique Boundary Critique Forces Critique Equations Done!! Drawing a force Hierarchical Feedback Free body Diagram Errors + All interactions between the system and objects outside the system boundary must be represented by forces. Hierarchical Feedback Free body Diagram Errors + All interactions between the system and objects outside the system boundary must be represented by forces. + The missing force is at a roller support. Hierarchical Feedback Free body Diagram Errors - All interactions between the system and objects outside the system boundary must be represented by forces. The missing force is at a roller support. - - The missing force is at the highlighted location. Video Explanations Buggy Rules Student FBD Correct Low-Level Errors Conceptual Diagnosis 1. Force in Wrong direction. 2. Missing 2 Forces. 1. “It appears that a body has been incorrectly modeled as a two-force member.” Buggy Rules W Student FBD Low-Level Errors 1. Forces are in the wrong direction. W Correct Conceptual Diagnosis 1. “Having a load does not cause all the forces to be in the opposite direction of it.” Solving a problem Create Boundary Draw Forces Write Equations Critique Boundary Critique Forces Critique Equations Done!! Writing an Equation Writing an Equation Type: Fx=0 Lever Writing an Equation Bx – D cos (u) = 0 Matching Equations Student Equation - F COS(U) + P SIN(U) = 0 ? Correct Equation - T COS(U) + F SIN(U) = 0 Matching Equations Student Equation - F COS(U) + P SIN(U) = 0 ? Correct Equation - T COS(U) + F SIN(U) = 0 Matching Equations Student Equation - F COS(U) + P SIN(U) = 0 ? Correct Equation - T COS(U) + F SIN(U) = 0 Outline • Introduction • Solving a problem • User Study • Results • Conclusion User Study Pretest NP2 Tutorial Posttest • Participants: • 101 students, working in pairs • UC Riverside statics course • Sessions: • 4 through out the quarter • Study in 3rd Session -- 30 min with NP2 User Study: Problems Problem A Problem B Improved Solution Time 32% Reduction Problem A Pretest Posttest 7.2 minutes 4.9 minutes 24% Reduction Problem B Pretest 7.3 minutes Posttest 5.6 minutes Solution Correctness: Problem A Couple modeled incorrectly Pretest Weight force incorrect Posttest Two-force member error Third Law error Pivot modeled incorrectly Other extra forces 0 0.5 1 Average Errors Per Student 1.5 Solution Correctness: Problem B Roller modeled incorrectly Pretest Weight force incorrect Posttest Two-force member error Third Law error Pivot modeled incorrectly Other extra forces 0 0.5 1 Average Errors Per Student 1.5 Ease of Drawing Easy 10 8 6 4 2 Hard 0 Boundary Arrows Labels Usefulness for Learning Very Useful 10 8 6 4 2 Not Useful 0 Equilibrium Two-Force Newton's Problems Member 3rd Law Forces Boundary Selection This Program… High 10 8 6 4 2 Low 0 Has Usable Is preferable Is easy Feedback to WIMP to learn Overall Reaction High 10 8 6 4 2 Low 0 Wonderful Easy Satisfying Stimulating Terrible Difficult Frustrating Dull Conclusion • Possible to scaffold handwritten work • Sketch recognition enables natural work environment … • Creating a solution rather than selecting the answer • Buggy-rules enable diagnosis of conceptual misunderstandings • NP2 is an effective tutorial system • Students like the interface • Measurable learning gains are quickly achieved This work is provided by the National Science Foundation via award No. 0735695. They also gratefully acknowledge support from HP, who provided the tablet PCs used in this project.