Final answer:
Motion is the change in an object's location over time and involves kinetics and dynamics. It is the result of a non-zero net external force that causes acceleration, as per Newton's first law.
Step-by-step explanation:
Motion is defined as the change in an object's location over time. This involves the concepts of dynamics, kinematics, and forces, which are all integral parts of understanding motion. Understanding motion and acceleration requires grasping the effects of external forces, as detailed by Newton's first law of motion which states that only a non-zero net external force can cause a change in motion, causing an object to accelerate.
Acceleration does not just refer to changes in speed; it also includes changes in the direction of movement. For example, in kinematics, if two ice skaters push against each other, the motion observed is the result after considering both magnitudes and directions of the forces involved. Dynamics, in particular, is concerned with how these forces cause the motion of objects and systems.
From our studies, it's clear that motion is not (A) or (B), as these define a state of equilibrium where forces balance to a net force of zero, which results in no acceleration and thus no change in motion. Option (D) describes a specific type of force, not motion. Therefore, (C) 'Change in an object's location over time' most accurately defines motion.