Which property is described as a body's resistance to changes in its state of motion?

Inertia is the property that describes a body's resistance to changes in its state of motion. It is a fundamental concept in physics, highlighting that an object at rest tends to stay at rest, and an object in motion tends to remain in motion at a constant velocity unless acted upon by an external force. This concept is grounded in Newton's First Law of Motion, which states that an object will not change its state of motion unless acted upon by a net external force.

Understanding inertia is crucial in various aerospace applications, as it directly relates to how spacecraft and aircraft behave during maneuvers, launches, and landings. The body's mass determines the amount of inertia it has: the greater the mass, the greater the inertia, making it more resistant to changes in its motion. This is essential knowledge when calculating forces and designing systems that account for the motion of different bodies under various conditions.