What is Newton's First Law of Motion?

Newton's First Law of Motion articulates the concept of inertia, which states that an object will maintain its state of rest or uniform motion in a straight line unless acted upon by an external force. This principle highlights that without any net external forces, there is no change in motion for the object.

In practical terms, this means that if you have a stationary object, like a book on a table, it will not move unless something pushes or pulls it. Likewise, if a ball is rolling on a frictionless surface, it will keep rolling indefinitely at the same speed and in the same direction until an external force, such as friction or another object, interferes with its motion.

The other provided options do not accurately reflect the law. Some incorrectly emphasize concepts like speed of light or motion stopping without other forces, which do not align with the fundamental principles described in Newton's First Law. The choice that highlights the necessity of an external force to change an object’s state of motion is the one that truly represents the law.