Tutorial 2 MECH 101 Liang Tengfei [email protected] Office phone : 2358-8811 Mobile : 6497-0191 Office hour : 14:00-15:00 Fri 1 General Equilibrium Problems Equilibrium Conditions: F 0 M 0 F 0 F 0 M 0 x 2D: y z Today we will focus on: How to select the free body? How to draw the free body diagram? How to build up equations? 3D: F F F x 0 y 0 z 0 M M M x 0 y 0 z 0 Example 1 Determine the reactions at point A and B Isolate the free body & use reactions to replace the connections. Set up equations (resolve, sum) A Example 2 Draw Free Body Diagram (access: # unknow=# equation) Answer: Ay=183N Ex=0, Ey=417N, ME=-500N.m Example 3 The wall crane supports a load of 3.5KN. Determine the horizontal and vertical components of the reaction at pins A and D. Also, what is the force in the cable at the winch W? The jib ABC has a weight of 500N and member BD has a weight of 200N. Each member is uniform and has a center of gravity at its center. Answer: pulley E: T=1.75KN Member ABC :Ay=35KN Ax=9.966KN Member DB : Dx=9.116KN Dy=9.216KN C E 3.5KN Extra question If A and D are not in the same vertical line, how can we solve this problem?