The movement of objects can be described using motion graphs and numerical values. These are both used to help in the design of faster and more efficient vehicles.

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

Speed is the rate of change of distance - it is the distance travelled per unit time. Like distance, speed also does not have an associated direction, so it is a scalar quantity.

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 travel | Typical speed in m/s |
---|---|

Walking | 1.5 |

Running | 3 |

Cycling | 6 |

Car | 13-30 |

Train | 50 |

Aeroplane | 250 |

It is not only moving objects that have varying speed. 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 average speed of a moving object can be calculated using the equation:

This is when:

- average speed (
*v*) is measured in metres per second (m/s) - distance travelled (
*s*) is measured in metres (m) - time (
*t*) is measured in seconds (s)

A car travels 500 m in 50 s, then 1,500 m in 75 s. Calculate its average speed for the whole journey.

First calculate total distance travelled:

Then calculate total time taken:

Then use

To find *v*:

It is important in motion calculations to be able to easily convert between units, in particular between metres and kilometres, and seconds and hours.

1 metre is equal to 0.001 kilometres so to convert from metres to kilometres - divide by 1,000.

1 kilometre is equal to 1,000 metres so to convert from kilometres to metres - multiply by 1,000.

1 hour is equal to 3,600 seconds so to convert from hours to seconds - multiply by 3,600.

For example:

- Question
Convert the following into kilometres:

- 12,300 m
- 5,389 m
- 252 m
- 64 m

Answers

- 12,300 m = 12.3 km
- 5,389 m = 5.389 km
- 252 m = 0.252 km
- 64 m = 0.064 km

- Question
Convert the following into seconds:

- 1.5 h
- 12 h

- 1.5 h = 5,400 s
- 12 h = 43,200 s

- Question
Convert 1 m/s into km/h.

- 1 m/s = 3,600 m/h
- 3,600 m/h = 3.6 km/h