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Unformatted text preview: COE 2001 — Test 3 — Summer 2007 Name: m PLEASE NOTE: 1. 3????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 “lb—force” in this test, NOT “lb—mass” (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. Pb. I (40 pts) , The truss below is symmetric about the line KM. Please answer the following questions: 1. 3. Find the angles a and [5 (Hint: CF intersects the line KM in its middle) Find the force in member KI using the method of joints. Specify if that member is in tension or compression.
Find the force in member CF using the method of sections (gin; cut horizontally through EC, CF and FD).
Clearly draw the FBD of the piece of truss you will apply equilibrium to. Specify if member CF is in tension or
compression. Which members in this truss are zero force members? 4 2
+2—5CJ") +2“?ng20 Pb II (30 pts)— The fr_ame ACFGEB drawn below represents a lightweight, foldable ladder proppeﬁ on a smooth
(frictionless) floor. It IS made of 4 bars: AICF, FG, CDE, and BEG. Its weight of 10 lbs 15 acting at D which IS the
middle point of bar CDE. A woman weighing 120 lbs has climbed 40% of It and IS stationery at pomt I 1. Draw a FBD for the ladder as a whole, and for each of its 4 members (so you must draw 5 FBDs total). Does
the ladder have any two force members, and if so, which are they? 2. Apply equilibrium to the entire ladder and solve for the forces at A and B. 3. Find angle B (Hi__n_'t. consider the 2 right angle triangles whose hypotenuses are AI and AF, and use the fact that
AI/AF= 0.4) as well as the horizontal distance between A and C. 4. Apply equilibrium to a wellchosen member of the ladder and solve for the force in FG m. What can you say
about this member? F G C23 %:A+E'lﬁo_l0=c. a, +3314 :3cr4)[email protected]—,¢) 1100le is
azzmm Ar 91.6 OJ» ME wQ30 9k» Ail—Ci:
2 ,A @2341) 4— \20 (1143.4?) ._ M24) @Qkodicﬁgu mm, Cu SEEM l. Mlzjé ”17 u 51
ﬂ’ ‘0“? WWW .4 >2 Pb 111 (30 pts) — The archer’s left hand is pushing against the bow handle with a force P = 50 lbs. 1. Find the tension T in the string as a function of a.
2. Assume that a = 10 degrees. Find the internal loads (P, V, M) in the bow right above or below point B (do not
include the 50 lb force). Clearly indicate their direction and magnitude. ...
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 Spring '08
 VALLE

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