1. ME 221Lecture 231 ME 221 Statics Lecture #23 Sections 5.6 & 5.7

2. ME 221Lecture 232 Homework #8 Chapter 9 problems: –42, 43, 50 & 55 Chapter 5 problems: –11, 13, 16, 20, 24 & 25 Due Today

3. ME 221Lecture 233 Homework #9 Chapter 5 problems: –53, 54, 56, 62, 64, 69, 71 & 73 Due Friday, October 31

4. ME 221Lecture 234 Quiz #5 Today

5. ME 221Lecture 235 Last Lecture Equilibrium equations Free body diagrams 2- & 3-force members Modeling supports

6. ME 221Lecture 236 Today Equilibrium in 3 Dimensions Statically Indeterminate Reactions

7. ME 221Lecture 237 Equilibrium Equations We have examined 2-dimensional systems and analyzed their equilibrium conditions using the following: The equilibrium conditions we used may be expressed as:

8. ME 221Lecture 238 Equilibrium Equations For 3-dimensional systems, we use the same equilibrium equations, except we write them in vector form: The moment equation may also be written as: Where the couple C is the sum of all applied couples on the body

9. ME 221Lecture 239 Equilibrium Equations If there are more than 6 unknown forces or couples, the problem is statically indeterminate.

10. ME 221Lecture 2310 Solving Equilibrium Equations Draw a proper free body diagram Write each force and couple as a vector Draw position vectors from the origin to the line of action of each force Write the vector equations of static equilibrium – 6 equations, 6 unknowns

11. ME 221Lecture 2311 Statically Indeterminate Reactions Underconstrained system Cannot maintain equilibrium Overconstrained systems More unknown forces than equations

12. ME 221Lecture 2312 Quiz #5