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Name _________________________ Recitation Section _____ EMA 201 Quiz #1 - Semester II, 2002-03 This quiz is closed book and closed notes. Each problem is equally weighted. Please ask a proctor if you do not understand the calculator policy for quizzes. All work must be shown, including FBD?s. 1a) [40%] A utility pole supports wires that apply the 400 N and 650 N forces shown, and a guy wire applies force P. If the resultant force is to be vertical and P is to be as small as possible, determine the value a should have and the corresponding value of P. 30° 400 N 650 N P a b) [30%] The structure consists of a single cable wrapped around frictionless pulleys. The 100 N force is vertical. When determining the cable tension, a problem arises. Describe this problem, and its source. Show all FBDs needed and/or used. 4 3 100 N 4 3 A B C c) [30%] The specific weight of zinc die-casting alloy is 0.242 lb/in 3 . Determine the density of this material in kg/m 3 . Recall: g=rg. conversion factors 1 lb = 4.448 N 1 ft = 0.3048 m 1 in = 25.40 mm 1 slug = 14.59 kg 2) A system of symmetric cables and pulleys and spreader bar CE are used to lift a fragile architectural stone beam. If the only significant mass in the system is the 800 kg mass m of the beam, determine the forces in cables ACB and CDE, and the force in spreader bar CE. Show all FBDs needed and/or used. 30° F BA C D GF E 30° 60° 60° 45°45° m 3) When in equilibrium, plate BCD is horizontal. Determine the largest weight P the plate may have if the cables have the following breaking strengths: cable strength Show all FBDs AB 300 N needed and/or used. AC 200 N AD 200 N B x y z A C D 0.8 m P 0.8 m 0.9 m 0.9 m 1.2 m

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