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

							    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.