Q#2 review

From here on out, we will have a quiz every couple of chapters, so each will not cover too much material.

The chap 3-4 quiz will have:

• 2 2D problems
• 2 3D problems

Each problem will have

• 5 points for FBD's
• 15-25 points solving for M's and F's

What you need to know:

Forces at supports - don't memorize these, just think about what types of forces they can and cannot support!

2D examples:

3D examples:

Divide and Conquer!
Just take it one step at a time...


Steps for solving statics problems:
1. Draw a nice big FBD
2. List knowns
3. List unknowns
4. Figure out the geometry

• Find and label Θ's, lengths, etc.
• 2 sides + one Θ? Use law of Cosines
• 1 side and 3 Θ's? use Sine law
• Find unit vectors, split F's up into Fx + Fy + Fz

5. Apply equilibrium equ's:
                          Σ M = 0,  ΣF = 0

• Take your M about the point with the most unknowns to eliminate those unknowns from the M balance.
• Solve  Σ's with the fewest unknowns first.

6.  Check your answer

• Do the signs make sense?
• Do the magnitudes make sense?

Steps for Drawing a good FBD:

1.  Identify the object you want to isolate
2. Draw a sketch of the object isolated from it's surroundings
3. Draw vectors representing all of the external forces acting on the isolated object, and label them. 
          Understand reactions @ your supports and connections! 
4. Choose how to orient your coordinate system.
5.  Label all of your angles and distances.


2D Free Body Diagram Practice Problems:

 


 



3D Free Body Diagram Practice Problems:

2D Practice Problems:

 Start thinking about bridge designs...
What are the most effective ways to support weight?



Which of the below configurations puts the least stress on A?

3D Practice Problems: