Here's a breakdown:
* Inertia is a fundamental property of matter. It's the resistance to change in motion.
* At rest: An object at rest will stay at rest unless acted upon by an unbalanced force.
* In motion: An object in motion will stay in motion at a constant speed and direction unless acted upon by an unbalanced force.
Examples:
* A book sitting on a table will stay there unless you pick it up (an unbalanced force).
* A car traveling at a constant speed on a straight road will continue at that speed and direction unless brakes are applied, the steering wheel is turned, or another force acts upon it.
The concept of inertia is described by Newton's First Law of Motion, also known as the Law of Inertia.
