Which of the following describes inertia?

Inertia is fundamentally defined as the tendency of an object to resist changes in its state of motion. This means that an object at rest will remain at rest, and an object in motion will continue moving at constant velocity unless acted upon by an external force. This principle is a key component of Newton's First Law of Motion, which articulates how objects react when forces are applied to them.

The correct answer highlights this intrinsic property of matter, emphasizing that inertia is directly related to an object's mass; the greater the mass, the greater the inertia and the more force is required to alter its state of motion. This understanding of inertia is essential in various applications, from basic physics to engineering practices, as it informs how we predict and analyze the motion of objects under different conditions.

In contrast to the other options, which focus on specific attributes or equations related to motion, the concept of inertia remains a broader and foundational idea that emphasizes resistance to change rather than quantifying motion itself or explicating the forces involved.