Which of Newton's laws states that an object in motion will stay in motion unless acted upon by an unbalanced force?

Newton's First Law, often referred to as the law of inertia, articulates that an object at rest will remain at rest, and an object in motion will continue in its motion at a constant velocity unless acted upon by an unbalanced external force. This principle emphasizes the concept of inertia, which is the tendency of objects to resist changes in their state of motion. In practical terms, this means that if no net force is applied to an object, its velocity—including both speed and direction—will remain constant.

This law is foundational in understanding how forces interact with motion and sets the stage for the other two laws of motion. It explains a wide range of phenomena, from why a car continues to move forward even after the driver has taken their foot off the accelerator to why a book on a table remains there unless pushed off.

The other options pertain to different concepts in physics: the Second Law relates force, mass, and acceleration; the Third Law states that for every action, there is an equal and opposite reaction; and the Law of Universal Gravitation describes the gravitational attraction between two masses. These concepts build upon the foundation set by the First Law but do not explicitly state the relationship of motion to unbalanced forces as clearly as the First