To develop the ability to break a frame or machine down into subsystems and to determine the forces developed at internal pin connections. Frames and machines are systems of pin-connected, multiforce members. Frames are designed to support loads, whereas machines are designed to transmit or alter the effects of loads. For a frame or machine to be in equilibrium, each member of the frame or machine system must be in equilibrium. Free-body diagrams of the overall system, as well as individual members, groups of members, and subsystems, must be drawn.