# ME 120 Engineering Mechanics I by WV05FP

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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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