Understanding Force Systems: Non-Coplanar Concurrent Forces

In mechanics, force systems are classified based on how the forces are arranged in space and their lines of action. Key classifications involve whether forces lie in the same plane (coplanar) or different planes (non-coplanar), and whether their lines of action intersect at a single point (concurrent) or not (non-concurrent).

Defining Key Terms

• Coplanar Forces: Forces whose lines of action lie in the same plane.
• Non-Coplanar Forces: Forces whose lines of action lie in different planes.
• Concurrent Forces: Forces whose lines of action all pass through a single point.
• Non-Concurrent Forces: Forces whose lines of action do not all pass through a single point.

Analyzing the Question's Description

The question describes a system of forces that:

• "meet at one point": This directly implies that the lines of action of all these forces pass through a single common point. This is the definition of concurrent forces.
• "have their lines of action in different planes": This means the forces do not all lie within a single plane. This is the definition of non-coplanar forces.

Combining these two conditions, we are looking for a force system that is both non-coplanar and concurrent.

Evaluating the Options

Let's examine the given options based on our understanding:

1. Coplanar non-concurrent forces: These forces lie in the same plane but do not intersect at a single point. This does not match the description of forces meeting at one point.
2. non - coplanar concurrent forces: These forces meet at one point (concurrent) and lie in different planes (non-coplanar). This perfectly matches the description provided in the question.
3. non - coplanar non-concurrent forces: These forces lie in different planes and do not intersect at a single point. This does not match the description of forces meeting at one point.
4. intersecting forces: While concurrent forces are indeed intersecting forces (they intersect at the point of concurrency), this term is more general and does not specify whether they are in the same plane or different planes. The question specifically mentions "different planes". Therefore, "non-coplanar concurrent forces" is the more precise classification.

Based on the analysis, the forces which meet at one point and have their lines of action in different planes are called non-coplanar concurrent forces.