Speed

This lesson covers: 

  1. What speed measures
  2. How to calculate speed using the speed equation

What is speed?

Speed tells you how fast an object is moving.

It measures the distance travelled by an object divided by the time taken.

  • The formula triangle shows the relationship between speed, distance and time.
  • Use the word SIDOT to remember: Speed Is Distance Over Time.
  • So speed equals distance divided by time so the formula is: Speed = TimeDistance​

Units for speed

Speed can be measured in:

  1. Metres per second (m/s).
  2. Miles per hour (mph).
  3. Kilometres per hour (km/h).


These are all distance units per time unit.

Calculating speed

To calculate speed you need:

  • The distance travelled.
  • The time taken.

Then divide distance by time to get the speed.

Calculating speed example 1

Illustration of a sheep moving 10 metres in 5 seconds.

For example: A sheep moves 10 metres down a track in 5 seconds.


Step 1: Formula

speed = timedistance​


Step 2: Substitute in the known values

speed = 510​


Step 3: Complete the calculation

speed = 510​= 2 m/s

Calculating speed example 2

Illustration of a car traveling 15 miles in 30 minutes with an arrow indicating direction.

Calculate the speed of a car that travels 15 miles in 30 minutes. Give your answer in mph.


Step 1: Convert minutes to hours

To convert from minutes to hours, divide by 60

30 minutes = 0.5 hours


Step 2: Formula

speed = timedistance​


Step 3: Substitution

speed = 0.515​


Step 4: Evaluation

speed = 0.515​= 30 mph