Presentation on theme: "Lecture 43: Course Material Review"— Presentation transcript:
1 Lecture 43: Course Material Review ENGI 1313 Mechanics ILecture 43: Course Material Review
2 Final Exam Formulae Sheet Posted on course webpage Probably by end of MondayCoordinate with Dr. RideoutNot to be used in the final examFinal exam formulae sheet will be attached to the exam
3 Example 43-01The wheel weighs 20 lb and rests on a surface for which μB = 0.2. A cord wrapped around it is attached to the top of the 30-lb homogeneous block. If the coefficient of static friction at D is μD = 0.3, determine the smallest vertical force that can be applied tangentially to the wheel which will cause motion to impend.
4 Example 43-01 (cont.) FBD Possible Friction Analysis Cases Impending motion at BImpending motion at DImpending motion at B & DAssumption at BTTPWCWAFBFDNBND
7 Example 43-01 (cont.) Check Assumptions Maximum friction force at Point DCalculated force at Point DAssumption ok as block C does not have impending motionTWCFDND
8 Example 43-01 (cont.) Check Assumptions Block C tipping Therefore block does not tipTWCxND
9 Example 43-01 (cont.) Conclusion Impending motion at B Block C stationary and does not tip overTTPWCWAFBFDNBND
10 Example 43-02The friction hook is made from a fixed frame which is shown colored and a cylinder of negligible weight. A piece of paper is placed between the smooth wall and the cylinder. If θ = 20°, determine the smallest coefficient of static friction μ at all points of contact so that any weight W of paper p can be held.
11 Example 43-02 FBD Assume impending motion at all contact points F1 F1 WF2N1N2
13 Example 43-02 Analysis of Cylinder Objective is to Find Orient axes to contact surfaceyxF1 = W / 2rF2N1 = W / 2N2
14 Example 43-02 Analysis of Cylinder Objective is to Find Orient axes to contact surfaceyxF1 = W / 2F2N1 = W / 2 = 20N2
15 Example 43-03Determine the minimum force P needed to push the tube E up the incline. The tube has a mass of 75 kg and the roller D has a mass of 100 kg. The force acts parallel to the plane, and the coefficients of static friction at the contacting surfaces are μA = 0.3, μB = 0.25, and μC = 0.4. Each cylinder has a radius of 150 mm.
16 Example 43-03 (cont.) FBD Impending Motion Point A Point B Point C yxFBDImpending MotionPoint APoint BPoint CPoint B and CWNAFAFANAWFANAPFANA
17 Example 43-03 (cont.) Analysis Assume impending motion at point A FBD of rollerFBD of cylinderWr = 0.15mNAFBFANBWFANAr = 0.15mPFCNC
18 Example (cont.)yxAnalysis of TubeWr = 0.15mNAFBFANB
19 Example (cont.)yxAnalysis of TubeWr = 0.15mNAFBFANB