what is inertia

Inertia is the tendency of objects in motion to stay in motion, and objects at rest to stay at rest, unless a force causes their speed or direction to change. It is one of the fundamental principles in classical physics, described by Isaac Newton's First Law of Motion. The term "inertia" comes from the Latin word "iners," meaning idle or sluggish. It is a passive property of a body by virtue of which it opposes any agency that attempts to put it in motion or, if it is moving, to change the magnitude or direction of its velocity. Inertia is not just a general law applicable only to objects with no forces acting upon them, but also a property of any object or body, in motion or at rest. An object's inertia determines what happens when a force is applied to it. Something with a lot of inertia, like a heavy, fast-moving object, will resist changing its motion, while an object with low inertia, such as a feather sitting on a table, is very easy to change its motion