Parallel force systems — same direction case Forces whose lines of action are parallel and point in the same direction are called:

Introduction / Context:Parallel force systems occur in beams, trusses under uniform loads, and multiple ropes lifting together. Proper naming clarifies how resultants are formed and where they act.

Given Data / Assumptions:

• Lines of action are parallel.
• All forces act in the same sense (e.g., all upward).

Concept / Approach:Parallel forces with the same sense are called “like parallel forces.” When they are in opposite senses, they are “unlike parallel forces.” “Coplanar concurrent/non-concurrent” describe intersection behavior and planarity, not the same-direction characteristic being tested here.

Step-by-Step Solution:Recognize parallelism and identical direction.Recall terminology: like parallel forces.Select option (c).

Verification / Alternative check:Resultant of like parallel forces equals the algebraic sum of magnitudes and acts in the same direction; its line of action is found using moments about a reference point, consistent with the definition.

Why Other Options Are Wrong:

• Coplanar concurrent forces intersect at a point, not generally true for parallel forces.
• Coplanar non-concurrent is broad and does not indicate direction sense.
• Unlike parallel forces are opposite in sense, not “same direction.”

Common Pitfalls:

• Mixing “parallel” classification with “concurrent” classification; they address different geometric relationships.

Final Answer:like parallel forces