Which term best describes an object needing a force to change its state of motion?

The term that best describes an object needing a force to change its state of motion is inertia. Inertia is defined as the property of an object to remain in its current state of motion, whether at rest or moving at a constant velocity, unless acted upon by an external force. This concept, rooted in Newton's First Law of Motion, implies that without the application of a force, an object will not change its motion.

For example, a stationary car will not start moving until a force, such as a push or the application of its engine power, acts upon it. Similarly, a moving vehicle will continue to travel at the same speed and in the same direction unless a force changes its motion, such as braking or turning. Understanding inertia is crucial in physics and helps explain why forces are necessary to initiate or alter motion.

Other options like momentum, kinetics, and acceleration relate to motion but do not directly encompass the idea of requiring a force to change the state of that motion as inertia does. Momentum refers to the quantity of motion an object has, kinetics deals with the forces and torques involved in the motion of bodies, and acceleration is the rate of change of velocity, which itself depends on the application of a force.