Concept
Independence of components — where it appears
The fact that motion along perpendicular directions can be treated separately, which is why a projectile's fall does not depend on its speed. It holds because the equations are linear and the axes uncoupled, and it fails the moment a force depends on the speed — as drag does.
Named by 2 essays across one field — each of them below, with the objects they name alongside it.
The angle that throws furthest, and why nobody notices
Forty-five degrees is the answer, and the maximum is so flat that a throw ten degrees off loses almost nothing. Both halves of that are worth drawing.
The slope, and the two directions that make it easy
An inclined plane looks like a harder problem than a flat one. Split the weight into two components chosen to suit the slope and it becomes an easier one.
Named alongside it
The objects these essays reach for when they reach for this one.
Air resistanceEnergy conservationFree-body diagramFrictionMechanical advantageNormal forceProjectile motionRange equationResolving vectorsStationary point