Final answer:
Inertia is the property of an object to maintain its state of rest or uniform motion in a straight line, as described by Newton's first law of motion. The more mass an object has, the greater its inertia, and hence, its resistance to changes in motion.
Step-by-step explanation:
Newton's First Law of Motion: Inertia
The tendency of a body to remain at rest or to maintain its motion in a straight line with constant velocity is referred to as inertia. This concept is encapsulated in Newton's first law of motion, which is often labeled as the law of inertia. The law states that an object will not change its state of motion unless a net external force is applied. This means that a body at rest will stay at rest, and a body in motion will continue to move at a constant speed in a straight line unless an outside force intervenes.
The measure of inertia an object possesses is directly related to its mass. The more mass an object has, the greater its inertia, making it more resistant to changes in its motion. Therefore, it takes a larger force to alter the velocity of a heavier object as compared to a lighter one. This principle is foundational in understanding motion and is pivotal in many areas of physics, from everyday phenomena to the depths of space.