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Shawn Kenny, Ph.D., P.Eng. Assistant Professor Faculty of Engineering and Applied Science Memorial University of Newfoundland ENGI 1313 Mechanics I Lecture 42:Course Material Review

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 2 Example If the resultant couple moment of the three couples acting on the triangular block is to be zero, determine the magnitudes of forces F and P.

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 3 Example (cont.) Technical Concept Couple Moment

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 4 Example (cont.) Analysis d d d

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 5 Example The telephone pole of negligible thickness is subjected to the force of 80 lb directed as shown. It is supported by the cable BCD and can be assumed pinned at its base A. In order to provide clearance for a sidewalk right of way, where D is located, the strut CE is attached at C, as shown by the dashed lines (cable segment CD is removed). If the tension in CD is to be twice the tension in BCD, determine the height h for placement of the strut CE.

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 6 Example (cont.) Technical Approach 2D Equilibrium FBD Complete FBD? Yes for initial condition Find T BD AyAy AxAx T BD

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 7 Example (cont.) Find T BD AyAy AxAx T BD

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 8 Example (cont.) Find T CD Find L CE Find h AyAy AxAx T CD T BD

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 9 Example The pipe is hoisted using the tongs. If the coefficient of static friction at A and B is μ s, determine the smallest dimension b so that any pipe of inner diameter d can be lifted.

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 10 Example (cont.) Global FBD FBD of Tong CyCy CxCx 0.5W FBFB NBNB FBFB FBFB W

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 11 Example (cont.) For Lifting CyCy CxCx 0.5W FBFB NBNB FBFB FBFB W

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ENGI 1313 Statics I – Lecture 42© 2007 S. Kenny, Ph.D., P.Eng. 12 References Hibbeler (2007) mech_1

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