Question

Moment equilibrium for the three force members will only be satisfied if_____________

(a) Three forces are in different dimensions

(b) The forces are in the same direction

(c) The forces are concurrent

(d) The forces are perpendicular

The question was posed to me by my college professor while I was bunking the class.

The doubt is from Two and Three Force Members in portion Equilibrium of a Rigid Body of Engineering Mechanics

Answer 1

The correct option is (c) The forces are concurrent

To explain I would say: The moment equilibrium for the three force members is satisfied only when the three forces are concurrent. That is the forces form a parallel system. That is the net force on the three axis turns out to be zero. This will only happen if the forces are in the same plane.