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Unformatted text preview: COE 2001 — Test 2 — Summer 2007 Name: KEV PLEASE NOTE: 1. .°°.“?‘S":'“E“E" If axes are speciﬁed for a given problem, you are to use them. Do not change them in any way or you get a 0
(zero) to that question. Show all work. If you make an assumption, state it clearly. Provide units with your answers, and box them. Use the back of the equation sheet as scrap paper if needed. The “lb” unit means “lbforce” in this test, NOT “lbmass” (i.e. do NOT multiply by gravity to get a force!).
Deﬁne clearly any new variable you introduce in a problem based on the givens. For the second problem, you are to use vectors to solve it, i.e. write forces and moment arms as vectors and calculate moments using cross products. Failure to comply will result in a 0 to the question even it you arrive at
the right answer in some dzﬂLerent manner. Pb. I (50 pts) — The ﬁxed beam below is supported by a thick wall. You are to assume that the wall primarily
supports the beam by 2 distributed forces as shown below, one triangular and the other constant, both of unknown magnitudes; and a horizontal force. There are no moments at the wall support. 1. Draw a FBD of the beam.
Apply equilibrium for this beam to calculate the unknown horizontal force and distributed forces’s magnitudes qT and qB.
Could you solve the problem if there was also an unknown moment at the wall? Justify your answer in one 21‘“ [olaN V
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’l’lddatex . ﬁ“_‘5® __ 2"— T 6 . > > Pb 11 (50 pts) — The rear door of the station wagon pictured below is held up when open by the two gasﬁlled struts
attached to the car by ball & socket joints. Part (9% of the door weighs 90 lbs (acting at its geometrical center) and part .5 weighs 60 lbs (also acting at the geometrical center — for simplication, neglect the thickness of part .5). We
want to calculate the forces in the struts. Please answer the following questions: 1. 2.
3. .°°>‘.°‘ The struts are 2 force members. Are they in tension or compression, and why? Based on your answer,
draw the FBD of one of them (it doesn’t matter which one). Based on the geometry, what can you say about the force in each strut, and why? Draw a FBD of the door (in 3D). How many unknows do you have? What does that mean for solving for
the unknown strut forces? Calculate the coordinates of A, B, C, as well as those of GA (center of gravity for part r? of the door) and GB
(center of gravity for part ’5’ of the door). What is the xcoordinate of GA and GB? Do you need the
coordinates of D, E, H? Express the weights of parts 5? and .25 as vectors. Based on the geometry, what can you do to their
magnitudes and still get the right value for the forces in the struts? Express the force F in strut BC as a vector with unknown magnitude F. Solve for F using a moment equation about a judicious line (which is it?) What happens in this problem if you use the moment equation at a point (which would you pick?), rather
than about the line you chose in the previous question? (D A C» {1/ o, o)
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This note was uploaded on 11/04/2009 for the course COE 2001 taught by Professor Valle during the Spring '08 term at Georgia Tech.
 Spring '08
 VALLE

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