# Scalar and vector quantities

## Scalars

Scalar quantities have only magnitude (size).

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

There are many scalar quantities:

• time
• power
• energy

Scalar quantities change when their magnitude changes.

## Vectors

Vector quantities have both magnitude (size) and .

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

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

• force
• momentum

Vector quantities change when:

• their magnitude changes
• their direction changes
• their magnitude and direction both change

## Example

A 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