# Speed and velocity

## Speed, distance and time

is how far an object moves. It does not include an associated direction, so distance is a quantity.

is the of distance – it is the distance travelled per unit time. Like distance, speed does not have an associated direction, so it is a scalar quantity.

### Typical speeds

When people walk, run, or travel in a car their speed will change. They may speed up, slow down or pause for traffic. The speed at which a person can walk, run or cycle depends on many factors including:

• age
• terrain
• fitness
• distance travelled

Some typical values for speed in metres per second (m/s) include:

Method of travelTypical speed in m/s
walking1.5
running3
cycling6
car13 - 30
train50
aeroplane250

It is not only moving objects whose speed can vary. The speed of the wind and the speed of sound also vary. A typical value for the speed of sound in air is about 330 m/s.

The of an object is its speed in a particular direction. Velocity is a quantity because it has both a and an associated direction. To calculate velocity, is used in calculations, rather than distance.

Unlike distance, which is a scalar quantity, displacement is a vector quantity. It includes:

• the distance travelled, measured in a straight line from start to finish
• the direction of the straight line