The motion of objects can be analysed using equations and graphs. These tools allow other aspects of motion such as acceleration and displacement to be determined or modelled.

Part of

Scalar quantities have only magnitude (size).

For example, 11 m and 15 m s^{-1} are both scalar quantities.

There are many scalar quantities:

Scalar quantities change when their magnitude changes.

Vector quantities have both magnitude (size) and direction.

For example, 11 m east and 15 ms^{-1} at 30° to the horizontal are both vector quantities.

There are many vector quantities. This guide will use the following six:

- displacement
- velocity
- acceleration
- force
- weight
- momentum

Vector quantities change when:

- their magnitude changes
- their direction changes
- their magnitude and direction both change

A geostationary satellite is in orbit above the Earth. It moves at constant speed but its velocity is constantly changing (since its direction is always changing).

- the difference in two scalar quantities = large value - small value
- the difference in two vectors quantities = final vector - initial vector