Regarding my question about software for drawing free-body diagrams:
It appears to me that the program FREEBODY by Graham Oberem is no
longer available. I did try writing to Dr. Oberem directly.
Obrik sounds very interesting but appears to be one of those open
source projects that isn't very active anymore. http://code.google.com/p/obrik/
This article sounds promising:
Roselli, R. J., Howard, L. and Brophy, S. (2006), A computer-based
free body diagram assistant. Computer Applications in Engineering
Education, 14: 281–290. doi: 10.1002/cae.20088