ME 120 Engineering Mechanics I Statics Professor David Quesnel Spring 2010 Exam 2 March 26, 2010 Name:________________________________________ Prob. #1 _________ Prob. #2__________ Prob. #3__________ Total ___________ Instructions: Answer all questions on the examination sheets. (use back if needed) Calculators Allowed but No Books & No Reference Sheet. Time: 50+5 minutes. ME 120 Engineering Mechanics I Statics Professor David Quesnel Spring 2010 ME 120 Statics Exam 2 1. (30 pts) Outriggers A and B are used to stabilize the crane from overturning when lifting large loads. If the load to be lifted is 3 Mg, determine the maximum boom angle so that the crane does not overturn. The crane has a mass of 5 Mg and center of mass GC, whereas the boom has a mass of 0.6 Mg and a center of mass at GB. FBD of System. Incipient tilting is when NB is zero. ME 120 Engineering Mechanics I Statics Professor David Quesnel Spring 2010 2. (35 pts) Determine the force in members CD and GF of the truss and state if the members are in tension or compression. Also indicate all zero-force members. Method of Joints or Method of Sections. Zero force members can be identified as DF, and given this, CF. Use sum of moments about ‘A’ to get Ey from an FBD of the entire truss. Then use method of sections, via moment equations, to solve for the two loads requested. Alternately, having identified the zero force members, realize that DE is the same as CD and EF is the same as GF so just use method of Joints at E. Here we show the method of sections: ME 120 Engineering Mechanics I Statics Professor David Quesnel Spring 2010 3. (35 pts) If the peg at B is smooth, determine the components of the reaction at the pin A and fixed support C. Draw the two FBDs of the pieces, noting that the force on the pin is locally perpendicular to the slot because it is smooth and thus to be modeled as frictionless.
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