Problem 1 A boat has a speed of 8 mph in still water attempts to go directly across a river with a current of 3 mph. What is the effective speed of the boat? A. 8.35 mph B. 8.54 mph C. 7.42 mph D. 6.33 mph

There are two questions to answer. The first question is a truss problem and the second is a frame problem. Upload homework solutions to both problems. Solutions must have free body diagrams and equilibrium equations and show each step.

Elementary beam theory predicts that the axial bending stress ox in a prismatic beam is given by: ox = (M.I,M,L)y+(M,I.-M.I.) (1,1₂-13/2) where My and M₂ are bending moments applied to a cross-section, and where ly, lz and lyz are second moments of area in the usual notation (Oxyz is a Cartesian coordinate system in which the x axis corresponds to the centroidal axis of the beam). (iii) A Z--section beam has the cross-section shown overleaf (see Figure QB2). The second moments of area of the section about the y and z axes are given as;; ly = 1.12x106mm² and I₂ = 2.87x106 mm4. Show that lyz = 1.35x106 mm² (use the parallel axis theorem). 100 60 10 y -10 10 60 Figure QB2 N (iv) Bending moments Mz = 2.0 kNm and My = 0 kNm act on a cross- -section of the beam of part (iii). Obtain an expression for the bending stress and sketch the orientation of the neutral axis with reference to the y and z axes. What is the maximum tensile value of the axial bending stress and where does it occur?

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