Speed is the measurement of how far an object travels in a specific time. So, to determine the speed of an object, there are two measurements that are required:
- The distance that the object has travelled.
- The time taken to cover this distance.
When these measurements have been taken, then the speed can be calculated using the following equation.
A car travelling on a motorway covers a distance of 200 metres in just four seconds. How fast is the car travelling?
The speed is equal to 200 ÷ 4 = 50 m/s (metres per second)
A motorbike travels a distance of 150 miles in 2.5 hours. What was the bike's average speed?
The speed is equal to 150 ÷ 2.5 = 60 mph (miles per hour)
The speed calculated by this method is an average speed because the car or bike may have been accelerating or decelerating or both over the distance.
Metres per second (m/s) is a commonly used unit to measure speed, but you are probably more familiar with miles per hour (mph) or kilometers per hour (kmh) when referring to the speed of cars. All of the units for speed are a distance unit divided by a time unit.