What does Newton's First Law of Motion state?

Newton's First Law of Motion states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This law can be captured in two key ideas: first, that an object in motion stays in motion, and second, that an object at rest remains at rest. Both elements reflect the principle of inertia, which describes an object's tendency to resist changes in its state of motion.

The first part, "an object in motion stays in motion unless acted upon," emphasizes that once an object is in motion, it will continue to move unless something causes it to stop or change direction. The second part, "an object at rest remains at rest unless acted upon by a force," reinforces the concept that a stationary object will not begin to move without a force influencing its state.

Thus, choosing both aspects together as the correct answer captures the essence of Newton's First Law. This comprehensive understanding of inertia provides a foundational principle for further study in physics.