PowerPoint PresentationHomework #11Homework #12Quiz #7No Class Wednesday, November 26No Class Friday, December 5 Mechanical Engineering Design Conference MSU Union 9am to noon Demonstrations 1pm to 2pm Awards in Ballroom ME371 Mechanical Design I ME412 Heat Transfer Lab ME456 Mechatronics Systems Lab ME471 Mechanical Design II ME481 Mech Engineering Design ProjectsChapter 8 - FrictionFriction AngleSlide 9Coulomb Friction (dry friction)Common Static Friction CoefficientsExample ProblemSlide 13Friction: WedgesME221 Lecture 34 1ME 221 StaticsLecture #34Sections 8.1 – 8.2ME221 Lecture 34 2Homework #11Chapter 6 problems:–2, 3, 6 & 7 – Method of Joints–32, 36, 47 & 53 – Method of Sections–68 & 75Due TodayME221 Lecture 34 3Homework #12Chapter 8 problems:–1, 2, 4, 8 & 15Due Monday, December 1ME221 Lecture 34 4Quiz #7TodayAnalysis of StructuresMethod of Joints orMethod of SectionsME221 Lecture 34 5No ClassWednesday, November 26ME221 Lecture 34 6No ClassFriday, December 5Mechanical Engineering Design ConferenceMSU Union 9am to noon Demonstrations1pm to 2pm Awards in BallroomME371 Mechanical Design IME412 Heat Transfer LabME456 Mechatronics Systems LabME471 Mechanical Design IIME481 Mech Engineering Design ProjectsME221 Lecture 34 7Chapter 8 - Friction•Overview•Coulomb friction (dry friction)–Static and kinematic•Fluid friction–Wedges–TypesME221 Lecture 34 8Friction Angle•A body on an incline, acted upon by gravity alone, will slip at an angle related to the coefficient of frictionNfW•From the FBD: N – W cos α = 0 & ƒ – W sin α = 0 •Such that: ƒ = N tan α (friction force)ME221 Lecture 34 9Friction Angle•The Coefficient of Static Friction (s) is defined as the tangent of the maximum angle a body may be inclined before slip occurs NfWs = tan max = ƒmax / N•The angle max is called the friction angleME221 Lecture 34 10Coulomb 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 34 11Common Static Friction CoefficientsSteel on steel 0.75Rubber on concrete 0.5-0.9Rubber on ice 0.05-0.30Metal on wood 0.2-0.6Teflon on Teflon0.04Tires on gravel 0.5ME221 Lecture 34 12Example ProblemME221 Lecture 34 13Quiz #7ME221 Lecture 34 14Friction: Wedges•Wedges are a simple means for lifting•Again, friction force opposes the motion•Disassembled FBDs are essential for solving wedge problems–Apply equilibrium equations to disassembled FBDs•Examples: 8.71, 8.72, 8.80,