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Speed: Formula and units

Tutor: Labib

# Speed: Formula and units

## In a nutshell

Speed is a measure of how much distance is travelled within a certain amount of time.

## Formula for speed

The formula to calculate speed is:

$speed=\frac{distance}{time}$

Or, more simply:

$S=\frac{D}{T}$

## Units of speed, distance and time

#### units

Speed

metres per second ($m/s$​), kilometres per hour ($km/h$​), miles per hour $(mph)$​​

Distance

metres ($m$​), kilometres ($km$​), miles ($miles$​)

Time

seconds ($s$​), hours ($h$​)

## Solving speed problems

To solve problems involving speed, follow this procedure:

#### procedure

 1 Identify what values you have and what variable you want to find. 2 Rearrange the speed formula for the desired variable. 3 Substitute in known values. 4 Give the answer with the correct units.

##### Example

A car has travelled 250 kilometres in 5 hours. What was the speed of the car?

From the given information, identify the distance and the time:

$D=250km,\,T=5$ hours

Write the speed formula (no need to rearrange as it's already given in terms of speed):

$S=\frac{D}{T}$

Substitute in the known values:

$S=\frac{250km}{5h}$

Give the answer with the correct units:

$\underline{S=50km/h}$

## FAQs - Frequently Asked Questions

### What is speed?

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