Newton's first law of motion is also known as _____.

Law of Inertia 

The correct answer is option 3. Law of Inertia.

Newton's first law of motion, often referred to as the Law of Inertia, is a fundamental principle in physics that describes the behavior of objects when no external forces are acting upon them.

Newton's first law of motion states, "An object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity along a straight line, unless acted upon by an external force."

The key concept in Newton's first law is inertia. Inertia is the tendency of an object to resist changes in its state of motion. An object at rest (with zero velocity) tends to stay at rest, and an object in motion (with constant velocity) tends to continue moving at the same velocity in a straight line.

When the forces acting on an object are balanced (resultant force is zero), there is no net force to cause a change in motion. Therefore, the object will maintain its state of motion, whether it is at rest or moving with a constant velocity.

Examples: If a book is placed on a table, it remains at rest because the force of gravity pulling it downward is balanced by the normal force exerted by the table upward.

Newton's first law of motion serves as the basis for understanding the behavior of objects in various situations. It explains why objects stay at rest or continue moving unless acted upon by external forces. This law is essential in analyzing the dynamics of objects in physics and engineering, from simple everyday scenarios to complex systems.

In summary, Newton's first law of motion, also known as the Law of Inertia, describes the natural tendency of objects to maintain their state of motion unless influenced by external forces. It forms the foundation of classical mechanics and plays a crucial role in understanding motion and dynamics.