What describes the tendency of an object to resist a change in motion?

The tendency of an object to resist a change in its state of motion is known as inertia. This concept is a fundamental principle in physics, particularly in the study of motion. Inertia is directly related to mass; an object with greater mass has more inertia and thus requires a larger force to change its motion compared to an object with less mass. This means that whether an object is at rest or moving at a constant speed, it will remain in that state unless acted upon by an external force.

For example, a heavy train moving at a consistent speed will not suddenly stop or change direction without an applied force, demonstrating its inertia. In summary, inertia is crucial in understanding how and why objects behave the way they do when forces are applied, making it a key concept in classical mechanics.