Vector

Vector quantities have both size (magnitude) and direction. They are represented by arrows whose length shows the magnitude and whose direction shows the direction.

Common vectors: displacement, velocity, acceleration, force, momentum, weight.

Vectors in the same direction are added. Vectors in opposite directions are subtracted. Vectors at right angles are combined using Pythagoras’ theorem and trigonometry.

The distinction between scalar and vector matters because direction affects outcomes (e.g. two forces can cancel if opposite, but two energies always add).