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600 N A 3 m QUESTION 1 (25 marks) 1.8 m 1.8 m- External forces are applied to a pin-jointed truss, supported by frictionless rollers at E and hinged at D, as shown in Figure 1. B C D (a) Identify all zero-force members without any calculation. (3 marks) (b) Determine the roller reaction at E, with the aid of a free- body diagram of the entire truss. (3 marks) Determine, stating whether the members are in tension or compression: a H 40⁰ G F 500 N E (c) the force in member EF, using the Method of Joints, with the aid of a free-body diagram of the relevant joint, 450 N Figure 1 (2 marks) (d) the forces in member BC, CG and GF, using the Method of Sections, with the aid of a free-body diagram of the relevant section, and (11 marks) (e) the forces in member CF and DF, using the Method of Joints, with the aid of a free-body diagram of the relevant joint. (6 marks) Ans: AB, AH, DE, 1885.4 N (←), - 1885.4 N (C), 173.6 N (T), 1037 N (T), - 1051.8 N (C), -889.54 N (C), 1620.4 N (T) 1.8 m wwwxx