What principle is outlined in Newton's First Law?

Newton's First Law of Motion, often referred to as the law of inertia, states that an object at rest will remain at rest and an object in motion will continue moving at a constant velocity in a straight line unless acted upon by a net external force. This law emphasizes the concept of inertia, which is the tendency of an object to resist changes in its state of motion.

The rationale behind this principle is that objects have a natural tendency to maintain their current state, whether it is at rest or in motion, until an unbalanced force, such as friction or applied force, causes a change. This foundational concept is critical in understanding how forces interact with objects in both aviation and physics in general.

In this context, it's important to recognize that the other options pertain to different principles of motion and are not part of Newton's First Law. For instance, the third statement relates to Newton's Second Law (force equals mass times acceleration), while the fourth statement describes Newton's Third Law of Motion (for every action, there is an equal and opposite reaction).