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

Solving a problem Create Boundary Critique Boundary Draw Forces Critique Forces Write Equations 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 Critique Boundary Draw Forces Critique Forces Write Equations Critique Equations Done!!

Drawing a force

+ All interactions between the system and objects outside the system boundary must be represented by forces. Free body Diagram Errors Hierarchical Feedback

+ + All interactions between the system and objects outside the system boundary must be represented by forces. The missing force is at a roller support. Free body Diagram Errors Hierarchical Feedback

- - - 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. Free body Diagram Errors Hierarchical Feedback

Video Explanations

Buggy Rules Student FBD 1.Force in Wrong direction. 2.Missing 2 Forces. Low-Level Errors Correct Conceptual Diagnosis 1. “It appears that a body has been incorrectly modeled as a two-force member.”

Buggy Rules W W Correct Student FBD 1.Forces are in the wrong direction. Low-Level ErrorsConceptual Diagnosis 1.“Having a load does not cause all the forces to be in the opposite direction of it.”

Solving a problem Create Boundary Critique Boundary Draw Forces Critique Forces Write Equations Critique Equations Done!!

Writing an Equation

Type: Fx=0 Lever

Writing an Equation Bx – D cos (u) = 0

Matching Equations - T COS(U) + F SIN(U) = 0 - F COS(U) + P SIN(U) = 0 Student Equation Correct Equation ?

Matching Equations - T COS(U) + F SIN(U) = 0 - F COS(U) + P SIN(U) = 0 Student Equation Correct Equation ?

Matching Equations - T COS(U) + F SIN(U) = 0 - F COS(U) + P SIN(U) = 0 Student Equation Correct Equation ?

Outline Introduction Solving a problem User Study Results Conclusion

Pretest NP2 Tutorial Posttest User Study Participants: 101 students, working in pairs UC Riverside statics course Sessions: 4 through out the quarter Study in 3 rd Session min with NP2

User Study: Problems Problem A Problem B

Improved Solution Time PretestPosttest 7.2 minutes 4.9 minutes PretestPosttest 7.3 minutes 5.6 minutes Problem A Problem B 32% Reduction 24% Reduction

Solution Correctness: Problem A

Solution Correctness: Problem B

Ease of Drawing LabelsArrowsBoundary Easy Hard

Usefulness for Learning Equilibrium Problems Two-Force Member Newton's 3rd Law ForcesBoundary Selection Not Useful Very Useful

This Program… Has Usable Feedback Is preferable to WIMP Is easy to learn High Low

Overall Reaction Stimulating Dull Satisfying Frustrating Easy Difficult Wonderful Terrible High Low

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 They also gratefully acknowledge support from HP, who provided the tablet PCs used in this project.