What is defined as the interaction between two bodies resulting in acceleration or deceleration?

The interaction between two bodies that causes acceleration or deceleration is best defined as force. In physics, force is understood as a vector quantity that results in the change of motion of an object. When a force is applied to an object, it either accelerates the object, causing it to speed up, or decelerates it, causing it to slow down. This relationship is grounded in Newton's Second Law of Motion, which states that force equals mass times acceleration (F = ma).

This understanding of force is crucial in fields like corrective exercise, as it helps professionals comprehend how to effectively apply therapeutic interventions to influence the movement patterns and overall mechanics of their clients. The other terms—mass, momentum, and velocity—have distinct definitions and do not specifically capture the concept of interaction leading to changes in motion in the same way that force does. Mass refers to the amount of matter in an object, momentum describes the quantity of motion an object has, and velocity indicates the speed and direction of an object’s movement. Hence, these concepts contribute to the dynamics of motion but do not depict the direct cause-and-effect nature of the interaction defined in the question.