2. The figure shows a traffic-light assembly with three identical 100-lb traffic lights at B, C, and D. The vertical and horizontal poles have negligible weight. Calculate the support reactions at the fixed support O. (Ignore the thickness of all poles when calculating distances.) 4 ft B 20 ft 100 lb 1600 20 ft A 2 ft 4 ft 30 ft 40 ft 5 ft D

The structure shown below is a simplified tower crane. It carries a shipping crate suspended from B that has a weight of 116 kN . The main jib DCB (in green) has a weight of 17 kN concentrated in the center of the beam. This is pinned to the main body at D and is supported by a cable that is routed through pulleys at F and G and is attached to a concrete counterweight J. The main body AEFG (in yellow) is fixed to the ground at A.   Various geometry: h1= 26.5 m h2= 3.9 m h3= 5.1 m l1= 12.8 m l2= 17 m l3= 4.3 mm θ= 57.6 degrees   Assumptions :  The main body AEFG can be considered massless. The cable CFGJ is massless. The pulleys at F and G can be considered massless, frictionless, and of negligible diameter. All bodies are considered rigid.   Questions:  Determine the weight of counterweight J in order for the main jib DCB to be horizontal. Determine the magnitude of the x and y components of force at pin D. Determine the reactions at fixed support A.

Problem 4c: Find the force P, required to maintain equilibrium in the position shown. Also find the support reactions in the bearings at A and B. The bearing at B supports thrust, while the bearing at A does not. 500 lb 150 lb 12 in. 12 in. 200 lb 18 in. 14 in. 14 in.

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