Force system classification — non-coplanar, non-concurrent forces Which description correctly defines non-coplanar non-concurrent forces?

Introduction / Context:
Classifying force systems helps determine the appropriate equilibrium conditions and solution methods. Non-coplanar non-concurrent systems are the most general in three-dimensional statics.

Given Data / Assumptions:

• Rigid-body statics in three dimensions.
• Forces can be characterized by concurrency (meeting at a point) and coplanarity (lying in one plane).

Concept / Approach:
A non-coplanar non-concurrent force system has no single point of intersection for all lines of action, and those lines of action do not lie in a single plane. Such systems require full 3D equilibrium equations: ΣF_x = ΣF_y = ΣF_z = 0 and ΣM_x = ΣM_y = ΣM_z = 0.

Step-by-Step Solution:

Verification / Alternative check:
Examples include forces acting on 3D frameworks with members not confined to a plane. Such systems cannot be reduced to 2D equations.

Why Other Options Are Wrong:

• Meet at a point but not coplanar: That would be a concurrent but non-coplanar system.
• Not concurrent but coplanar: That describes non-concurrent coplanar forces.
• Meet at one point and lie in the same plane: Concurrent coplanar, not asked.

Common Pitfalls:
Confusing concurrency with coplanarity; assuming that non-concurrent implies 3D automatically (non-concurrent can be purely 2D).

Final Answer:
Forces that do not meet at one point and their lines of action do not lie in the same plane