Statics — coplanar concurrent forces Which description correctly defines coplanar concurrent forces?

Introduction / Context:
Classifying force systems is essential for selecting the right equilibrium equations. “Coplanar concurrent” is a common case in 2D statics where ΣF_x, ΣF_y are sufficient and moments can be taken about the point of concurrency.

Given Data / Assumptions:

• All forces considered act in a single geometric plane.
• All lines of action intersect at a single point (concurrent).
• Rigid-body assumptions for statics.

Concept / Approach:
“Coplanar” means contained in one plane. “Concurrent” means all lines of action pass through one common point. In such systems, the resultant is obtained by vector addition, and equilibrium conditions reduce to ΣF = 0 at that point.

Step-by-Step Solution:

Verification / Alternative check:
Examples include cables meeting at a ring joint in a 2D truss node; solving requires balancing only two scalar components.

Why Other Options Are Wrong:

• Not coplanar / not concurrent: These describe spatial systems or non-concurrent cases requiring moment equations about arbitrary points.
• Parallel forces in different planes: Neither concurrent nor coplanar.

Common Pitfalls:
Confusing concurrent with parallel (parallel lines do not meet), or mixing spatial (3D) with planar cases.

Final Answer:
Forces that meet at one point and their lines of action also lie on the same plane