What principle states that a body remains at rest or moves uniformly unless acted upon by an external force?

What principle states that a body remains at rest or moves uniformly unless acted upon by an external force?

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

Answer: (A)

The principle that states a body remains at rest or moves uniformly unless acted upon by an external force is known as Newton's first law of motion. This law highlights the concept of inertia, which is the tendency of an object to resist changes in its state of motion. Essentially, it means that an object will not start moving, stop moving, or change its speed or direction unless a force is applied to it. This principle is foundational to classical mechanics, emphasizing the predictability of motion in the absence of external influences. It implies that if no net force is acting on an object, its velocity will remain constant — this could mean remaining still or moving in a straight line at a constant speed. In contrast, the second law introduces the concept of force and acceleration, specifically how the force applied to an object results in its acceleration depending on its mass. The third law states that for every action, there is an equal and opposite reaction, addressing interactions between two bodies rather than the motion of a single body. The law of conservation of momentum pertains to isolated systems and the constant total momentum therein, rather than the behavior of individual objects under external forces.

The principle that states a body remains at rest or moves uniformly unless acted upon by an external force is known as Newton's first law of motion. This law highlights the concept of inertia, which is the tendency of an object to resist changes in its state of motion. Essentially, it means that an object will not start moving, stop moving, or change its speed or direction unless a force is applied to it.

This principle is foundational to classical mechanics, emphasizing the predictability of motion in the absence of external influences. It implies that if no net force is acting on an object, its velocity will remain constant — this could mean remaining still or moving in a straight line at a constant speed.

In contrast, the second law introduces the concept of force and acceleration, specifically how the force applied to an object results in its acceleration depending on its mass. The third law states that for every action, there is an equal and opposite reaction, addressing interactions between two bodies rather than the motion of a single body. The law of conservation of momentum pertains to isolated systems and the constant total momentum therein, rather than the behavior of individual objects under external forces.