Classical mechanics

Classical mechanics is the part of physics that describes how everyday things move and how their motion changes because of forces. If we know how things are moving now, classical mechanics allows us to predict how they will move in the future and how they were moving in the past. We can use classical mechanics to predict how things like planets and rockets move.

Classical mechanics is not accurate when things are the size of atoms or smaller: for those things, we use quantum mechanics instead. Classical mechanics is also not accurate when things move close to the speed of light: for those things, we use special relativity instead.