Final answer:
The concept of a 'couple' in physics is a non-concurrent force system, as it comprises two forces that are parallel but do not share the same line of action. Newton's third law explains that forces come in pairs, whose effects depend on the system boundaries chosen for analysis. During events like a tug-of-war, when a rope snaps, the forces do not cancel as they act on separate systems.
Step-by-step explanation:
The statement 'a couple is a concurrent force system' is false. A couple consists of two parallel forces that are equal in magnitude, opposite in direction, and do not share the same line of action, thus creating a rotational effect. Since these forces are not acting along the same line, they cannot be concurrent. In contrast, a concurrent force system involves all forces acting at a single point or along a single line.
Newton's third law of motion states that forces always occur in pairs of equal and opposite magnitude. When analyzing a system, the choice of the "system of interest" dictates how these forces interact. Within a single isolated system, action-reaction pairs do not cancel out since they act on different parts of the system. However, if the system is considered to be part of a larger system, the internal forces can cancel each other out because they are equal and opposite.
During a tug-of-war, when the rope snaps, the forces involved illustrate Newton's third law. Each team is applying a force on the rope, and the rope applied an equal and opposite force back on each team. When the rope snaps, these forces no longer exist as the action-reaction pair has been broken. This demonstrates that the forces do not cancel out because they were acting on different systems - one on each team.
Choosing a system is crucial for understanding the physics of a problem. For example, consider a situation where the main forces acting are parallel or antiparallel to the center of mass. This could describe a car moving on a straight road where the primary forces are the thrust from the engine and the drag from air resistance. Both forces are along the line of motion (the direction the car is moving), affecting acceleration or deceleration.