A member that carries forces at exactly two points and has no external moment is called what?

• A. A two force member
• B. Three force member
• C. Forces and couples of a free body
• D. Truss

Answer: (A)

A member with forces applied only at its two ends and no external moment must carry a single axial force. With just two external forces acting on it and none of them being a moment, those forces have to be equal in magnitude, opposite in direction, and aligned along the line of the member. That means the member transmits force only along its length, in tension or compression, and does not bend or carry a moment. This is why such a member is called a two-force member. In structures like trusses, many members behave this way because joints are pinned, so the only external forces on each member are at its ends. If a third force or a moment were present, you wouldn’t have a two-force member.