Which of the following best describes Newton's first law?

• A. Force equals mass times acceleration
• B. An object at rest stays at rest, and an object in motion stays in motion
• C. For every action, there is an equal and opposite reaction
• D. Force is needed to maintain an object’s motion

Answer: (B)

Newton's first law of motion, often referred to as the law of inertia, states that an object will remain at rest or move in a straight line at a constant speed unless acted upon by a net external force. This law highlights the inherent resistance of objects to changes in their state of motion, whether that means staying at rest or keeping in constant motion.

The statement in the correct answer encapsulates the essence of this law, emphasizing the tendency of objects to maintain their current state unless influenced by an external force. This principle forms the foundation for much of classical mechanics and helps explain the behavior of objects in motion or at rest. Understanding this concept is crucial, as it lays the groundwork for further explorations into concepts of force, acceleration, and the interactions between objects in various physical scenarios.