ME221Lecture 121 ME 221 Statics Lecture #12 Sections 5.6 – 5.7

ME221Lecture 122 Homework #5 Chapter 9 problem: –43 Chapter 5 problems –11, 20, 56 & 69 –Due Monday, June 21 MatLab Group Problems –5.22, 5.37 & 5.58 –Due Monday, June 21

ME221Lecture 123 Quiz #5 Today

ME221Lecture 124 Exam #2 Monday, June 21

ME221Lecture 125 Chapter 5 Equilibrium of Rigid Bodies

ME221Lecture 126 Last Lecture Equilibrium equations Free body diagrams 2- & 3-force members Modeling supports

ME221Lecture 127 Today Equilibrium in 3 Dimensions Statically Indeterminate Reactions

ME221Lecture 128 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:

ME221Lecture 129 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

ME221Lecture 1210 Equilibrium Equations If there are more than 6 unknown forces or couples, the problem is statically indeterminate.

ME221Lecture 1211 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

ME221Lecture 1212 Statically Indeterminate Reactions Underconstrained system Cannot maintain equilibrium Overconstrained systems More unknown forces than equations

ME221Lecture 1213 Example

ME221Lecture 1214 Quiz #5