What is inertia?

Inertia is basically a measurement of how stubborn an object is about changin' its motion! Think of it as MOTION RESISTANCE—it's the natural law that says matter doesn't like being told what to do. If it's already movin' or sittin' still, it wants to keep doin' exactly that. This stubbornness has a MASS DEPENDENCY, meanin' the more stuff an object is made of, the harder it is to budge. A giant boulder has way more inertia than a pebble because it has more MASS to resist you. You can see this in a RESTING TENDENCY; objects at rest want to stay asleep forever unless somethin' forces them to wake up. On the flip side, there's a MOVING TENDENCY—once that boulder is rollin', its inertia makes it want to keep zippin' along at the same speed and direction. The only way to break this stubbornness is with a NET FORCE. When you push or pull hard enough to overcome that resistance, that's when the speed finally changes! Tiny Concepts.