What does Newton's First Law of Inertia state?

• A. Objects change direction only when a force is applied
• B. Objects remain at rest or motion unless acted upon by force
• C. Mass cannot change in motion
• D. An external force is necessary for all movements

Answer: (B)

Newton's First Law of Inertia states that an object will remain at rest or continue to move in a straight line at a constant speed unless acted upon by an external force. This fundamental principle underlines the concept of inertia, which is the property of an object to resist changes in its state of motion. In simple terms, if no net force is applied, a stationary object will not start moving, and a moving object will not change its velocity—meaning it won't accelerate, decelerate, or change direction.

This understanding is critical in fields such as physics and engineering, as it explains the behavior of objects in various situations, from vehicles on the road to celestial bodies in space. Newton's First Law lays the foundation for the concepts of force and motion, providing essential insights into how objects interact with one another in the absence of any influencing force.