Which law states that an object in motion will stay in motion?

• A. Newton's first law of motion
• B. Newton's second law of motion
• C. Newton's third law of motion
• D. Law of universal gravitation

Answer: (A)

The principle that an object in motion will remain in motion unless acted upon by an external force is articulated in Newton's first law of motion. This law describes the concept of inertia, which is the tendency of objects to maintain their state of rest or uniform motion in a straight line. According to this law, it is only when a net external force is applied that the motion of the object can change.

This foundational concept is crucial in understanding how forces interact with objects in both motion and rest. It sets the stage for more complex ideas in physics, including the behavior of objects under the influence of various forces. The other laws – the second and third laws – deal with different aspects of motion and force, such as the relationship between force, mass, and acceleration, and the interactions between two bodies, but they have different focuses and implications than the first law. The law of universal gravitation specifically addresses the gravitational attraction between masses but does not pertain to the motion of objects as defined in the first law.