Newton's First Law states that an object in motion will stay in motion unless acted upon by what?

Newton's First Law, also known as the law of inertia, states that an object at rest will remain at rest and an object in motion will continue to move in a straight line at a constant velocity unless acted upon by an unbalanced force. This principle highlights the concept that motion is not altered unless a net force acts on the object.

The key term in this law is "unbalanced force." It implies that for any change in the state of motion—whether that's starting, stopping, or changing direction—there must be a force that is not countered by an equal and opposite force. This idea is foundational in understanding how forces influence the motion of objects in our universe.