If the lines of action of the forces in a system meet at a point, these forces are called:

Asked in SSC JE 2010

Detailed Explanation

Force systems are named by how their lines of action are arranged: whether they lie in one plane (coplanar) and whether they meet at a point (concurrent) or are parallel.

Why “Concurrent forces” Is Correct

When all the lines of action pass through a single point — the point of concurrency — the forces are concurrent. Their resultant also passes through that point, and they produce no moment about it.

Force systems in a plane. Concurrent: lines of action meet at one point — such forces cannot produce a moment about that point. Parallel: lines of action are parallel — such forces cannot resist anything at right angles to them. Non-concurrent, non-parallel: the general case. A set of reactions that is all concurrent or all parallel cannot hold a body in every direction, so the body is improperly constrained.

Why the Other Options Are Wrong

A. Parallel forces: Parallel forces never meet (their lines of action are parallel).
B. Non-concurrent forces: Non-concurrent forces do not all meet at one point.
D. Resultant forces: The resultant is the single force that replaces a system; it is not a type of system.

Key Point

Lines of action meet at one point → concurrent forces.

Key Concepts for Students

Equilibrium of concurrent forces needs only ΣFx = 0 and ΣFy = 0.
Lami's theorem applies to three concurrent forces in equilibrium.
Coplanar forces lie in one plane.

Practice more: this is question 10 in Force Analysis MCQs – Part 1. Try the whole set and check every answer instantly.