# DEVELOPMENT OF AN INTERACTIVE FREE BODY DIAGRAM ASSISTANT FOR - PDF - PDF

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```							    DEVELOPMENT OF AN
INTERACTIVE FREE BODY
DIAGRAM ASSISTANT FOR
BIOMECHANICS

Robert J. Roselli1, Bryan Cinnamon2, Patrick
Norris1, Sean P. Brophy1, Derek Eggers2 and
Jerry Brock2
1Department of Biomedical Engineering,

Vanderbilt University, Nashville, TN
2Ntara, Inc, Johnson City, TN.
Motivation:
Newton's Laws:
ΣF = 0
ΣM = 0
are deceptively simple.

Identifying all forces and couples in
a particular problem can be
challenging!!
Free Body Diagram

Tool used to identify all forces and
couples in a problem
Illustration

What reactions keep the gymnast in this position?
Constructing a FBD

Step 1: Isolate body
Constructing a FBD

W

Step 2: Indicate External Forces
Constructing a FBD

W

N

Step 2: Indicate External Forces
Constructing a FBD

W

N

Step 3: Indicate Applied Couples
Constructing a FBD

W

C
N

Step 3: Indicate Applied Couples
Solution
Statics
? Forces = 0
? Momentsc = 0
y
h

X

?F = 0 = N - W
? Mc = 0 = 20cm*W - C

If all forces and couples are not placed on the
diagram, then the solution will be incorrect.
Free Body Diagram Assistant

• Asynchronous web tool
• Macromedia Flash 5
• SQL Server for data storage/retrieval
Free Body Diagram Assistant
Three Components

• Student interaction & feedback
• Authoring tool
• Administrative Area
Student Interaction with
FBD Assistant
Authoring Tool
Administration Area
Add a User
View
Sessions
Session Information and Diagnostics
Is the FBD Assistant
Effective?
FBD Assistant Survey

strongly
agree
5

4

3

2

1
strongly   The free body diagram tool helped me   Once I saw the final solution I was able to I usually remember to include moments
disagree    understand how to solve a free body   figure out what I had incorrect and I knew                and couples
diagram                                     why.
Performance Before and After use of the FBD Assistant

7

*
6

5                                    *
Average Score

4

*
*
3

2

1

0

pulley
4a-1                  4a-2
man                       4b-1
club               4b-2
golfer
Pre   Post

* p<0.05, paired t-test                                         E.S. = .45-.82
Summary

• We have developed an online tool
that guides students in the
development of free body diagrams.
• Students respond favorably to the
FBD Assistant.
• FBD Assistant is effective in
improving construction of free body
diagrams.
Future Plans for Improving the
FBD Assistant

• Improve Authoring Tool
• Use CAPE for advanced remediation
& tracking
• Develop a library of practice problems.

```
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