1. ME 221Lecture 81 ME 221 Statics Lecture #8 Sections 2.9 & 2.10

2. ME 221Lecture 82 Homework HW #3 Due Monday, September 15 –Chapter 2 problems: –61, 64, 70, 71, 72, 82, 86, 94, 105 & 113 Grades posted in Angel –HW #1 & Quiz #1 (and solutions) –HW #2 & Quiz #2 soon (solutions posted) –HW #3 solutions to be posted late Monday No late homework will be accepted once posted

3. ME 221Lecture 83 Exam 1 Wednesday, September 17 Details on Monday

4. ME 221Lecture 84 Particle Equilibrium For a particle to be in equilibrium, the resultant of the forces acting on it must sum to zero. This is essentially Newton’s second law with the acceleration being zero. In equation form:  F = 0

5. ME 221Lecture 85 Representing Equilibrium mimi Vector Diagram R = F 1 + F 2 + F 3 + F 4 = 0 Vector Equation F1F1 F2F2 F3F3 F4F4 F1F1 F2F2 F3F3 F4F4

6. ME 221Lecture 86 Representing Equilibrium Matrix Form x-components y-components z-components Component Form

7. ME 221Lecture 87 Statically Determinate For 3-D equilibrium, there are three scalar equations:  F x = 0,  F y = 0,  F z = 0 Problems with more than three unknowns cannot be solved without more information, and such problems are called statically indeterminate.

8. ME 221Lecture 88 Free-body Diagram A free-body diagram is a pictorial representation of the equation  F = 0 and has: –all of the forces represented in their proper sense and location –indication of the coordinate axes used in applying  F = 0

9. ME 221Lecture 89