PowerPoint PresentationHomework #12No Class Friday, December 5Quiz #8Final ExamChapter 8 - FrictionCoulomb Friction (dry friction)Friction: WedgesSlide 9WedgesExample ProblemME221 Lecture 36 1ME 221 StaticsLecture #37Sections 8.1 – 8.3ME221 Lecture 36 2Homework #12Chapter 8 problems:–1, 2, 4, 8 & 15 Due TodayME221 Lecture 36 3No ClassFriday, December 5ME221 Lecture 36 4Quiz #8TodayFriction problemME221 Lecture 36 5Final ExamSection 1 (3:00pm)Monday, 12/8, 3:00 – 5:00pmSection 2 (12:40pm)Wednesday, 12/10, 12:45 – 2:45pmSee University policy for multiple examsME221 Lecture 36 6Chapter 8 - Friction•Last Lecture•Coefficients – static & kinematic–Friction angle–Coulomb Friction•Today –WedgesME221 Lecture 36 7Coulomb Friction (dry friction)•Friction force (ƒ) is proportional to the normal force (N) and opposes motion •Coefficient of friction, , is the proportionality constant–Static coefficient, s–Kinematic coefficient, kkNsNPfPNfWf=PME221 Lecture 36 8Friction: Wedges•Wedges are a simple means for lifting•Again, friction force opposes the motion•FBDs are essential for solving problems–Apply equilibrium equations to FBDsME221 Lecture 36 9Friction: Wedges•Wedges may exert large normal forces•Used to lift heavy objects•Also used for splitting –Friction holds wedge in place•May be used in pairsME221 Lecture 36 10Wedges •The angle θ is called the wedge angle, and it determines the amount of force P required to raise the weight W, as well as the change in height of the weight as the wedge is driven into place. NfWP•In equilibrium (P = 0): ƒ cos θ – N sin θ = 0 •μs = tan θME221 Lecture 36 11Example