NETA Personal Trainer Practice Exam

Which principle explains that an object in motion continues to move at the same speed in the same direction unless acted upon by an external force?

1. Newton's first law of motion

2. Newton's second law of motion

3. Newton's third law of motion

4. Law of conservation of momentum

The correct answer is: Newton's first law of motion

The principle that describes an object in motion continuing to move at the same speed and direction unless acted upon by an external force is known as Newton's first law of motion. This law emphasizes the concept of inertia, which is the tendency of objects to resist changes in their state of motion. Essentially, it indicates that without the influence of an external force—such as friction, gravity, or a push or pull—an object will maintain its current velocity, whether that is at rest or in a state of uniform motion. Newton's first law forms the foundation of classical mechanics by highlighting the natural behavior of motion. It is crucial for understanding how and why objects move (or do not move) in a given environment, which is significant for personal trainers as they relate concepts of motion and force to exercise dynamics and body mechanics. Understanding this principle is important in fields such as physical training, as it provides insight into how changes in external forces—like added weights, resistance, or bodily movement—affect an individual's performance and physical responses during exercise.