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.