FBD Feedback Structure - mkraska/meclib GitHub Wiki
Feedback Structure
- Free Body Diagram
- Correct isolation of the system? All elements inside the system must be activated (visible), all adjacent elements of the environment must be deactivated (hidden, grey).
- Distributed loads ("q") must be deactivated and replaced by one or two resultants
- Value (expression as name),
- Direction,
- Location (must go through CG of the distributed load)
- Supports must be replaced by appropriate reactions
- Correct Name (based on support names, bar or rope names)
- Correct type (moment, force) and number
- Correct direction
- No spurious forces or moments (students might create a force outside the system and forgot to delete)
- Force and moment balance (equations of equillibrium)
- Expression for resultant forces and moments match the free body diagram
- Reference point for moment balance appropriately selected (such that two reactions go through that point)
- Solution for the unknown reactions, given as list of equations
- Are the balances satisfied? Apply
ev(balance, solution) - No tricky additional equations (solution might contain all zero reactions and setting the external load to zero).
- No spurious equations for other variables not being part of the problem (use fb_vars()).
- Are the balances satisfied? Apply
The input scaffold of the question should not give away too much of the solution.
- Name and number of the reactions
- Don't use them in the input description of their values. Use matrix input with equations
A_x=2*F
- Don't use them in the input description of their values. Use matrix input with equations
- Choice of reference point for moment balance
- Let the student indicate the reference point using cross hair