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

ME 221Lecture 82 Homework Due Monday, January 27 –Chapter 2 problems: –61, 64, 70, 71, 72, 82, 86, 94, 105 & 113 Grades posted in Blackboard –HW #1 & Quiz #1 (and solutions) –HW #2 & Quiz #2 soon (solutions posted) –HW #3 solutions to be posted late Monday

ME 221Lecture 83 Exam 1 Wednesday, January 29

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

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

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

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.

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

ME 221Lecture 89

ME 221Lecture 810 ME 221 Exam 1 Topics All of Chapters 1 & 2 except 2.11 Springs Newton’s Laws Units Scalars & vectors; defining, adding, etc. Laws of sine & cosine Resolution of a vector into components 3D coordinates & unit base vectors

ME 221Lecture 811 Exam 1 Topics continued Directional cosines Components of a vector in nonorthogonal terms Scalar products of two vectors 2-D and 3-D equilibrium problems draw a good free-body diagram

ME 221Lecture 812