Final answer:
Motion being the 'property of its mover' means that motion is relative and changes based on the chosen frame of reference, illustrating the principles of Newton's First Law of Motion, also known as the law of inertia.
Step-by-step explanation:
Understanding of Motion and its Reference
When the phrase 'motion is said to be the property of its mover' is encountered, it relates to the concept that motion depends on the frame of reference selected. This idea is grounded in the principles of Newton's First Law of Motion, which is also known as the law of inertia. Inertia is the property of a body to remain at rest or to continue moving at a constant velocity unless acted upon by a net external force. Therefore, motion is not an absolute property; it varies depending on the observer's point of view or frame of reference.
For instance, an object moving in a straight line at a constant speed is considered to be at rest or in uniform motion in an inertial frame of reference, such as inside a car traveling at a steady speed on a straight path. However, this same object can appear to be moving to an observer standing on the side of the road. This illustrates how motion is relative and emphasizes that it cannot be fully described without specifying the frame of reference.
To further clarify, motion at a constant velocity means the position of the object changes at the same rate over time. A car maintaining a constant speed on a highway demonstrates this. Newton's First Law is paradigmatic of the inertial reference frame concept, where an object either remains at rest or continues to move at a constant velocity in the absence of a net external force.