# An Introduction to Speed

#### Back to Physics Grade 9/10

## Description

This is a basic physics tutorial that is targeted at GCSE (grade 9 and grade 10) standard introducing the basic concepts of speed and how to calculate average speed of an object.

## What is speed?

You probably have some idea about what *speed* is: how fast something is travelling. The faster it's travelling, the greater its speed. If it slows down, its speed decreases.

In technical terms, speed is an attribute of a moving object. It tells us *how much distance the object is covering/moving within a specific period of time*. The greater the speed, the more distance it can cover within a specified time period.

## What is average speed?

An object will typically not travel at a constant speed; instead it will slow down and speed up in response to what's going on around it. For example, a car may slow down or stop during a journey if it comes to a red light at a traffic light.

Similarly, most people will tend to slow down as they start to climb a hill. *Average speed* takes all of these changes into account and tells you how fast the object was travelling *on average* during the journey.

## How do we calculate average speed?

To calculate an object's average speed over a journey you need to know how far it traveled, and how long it took to travel the distance; then you simply use the below equation:

**average speed = distance / time **

You can also describe this using the following equation:

#### v = s / t

where:

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

## Typical average speeds

On average, people will generally walk at a speed of 1 m/s, run at an average speed of 3 m/s, and cycle at an average of 6 m/s.

## Other units

Typically in scientific calculations we report time, distance and average speed using the units listed under the equation above, however this may change depending on the calculation. You can also use other units for distance and time, and thus for reporting average speed e.g. kilometers per hour (km/hr), or miles per hour (mi/hr). Just make sure that you __always include the unit__ in any reports, assignments or exam questions - without it your answer is useless.

Why not take a moment to practice what you've learned in the complementary free worksheet below?

## Exercise Worksheet

This worksheet has four exercises that you can work through in your own time, with answers given in meters per second, kilometers per hour and miles per hour. To download the document visit Slideshare here:

## Make notes

Want to make notes as you follow along? Visit Slideshare to download the document: