Speed (Edexcel IGCSE Physics (Modular))

Calculating average speed

• The speed of an object is the distance it travels every second

• Speed is a scalar quantity because it has a magnitude but not a direction

Average speed

• The speed of an object can vary throughout its journey

• Therefore, it is often more useful to know an object's average speed

A hiker might have an average speed of 2.0 m/s, whereas a particularly excited bumble bee can have average speeds of up to 4.5 m/s

Average speed formula

• The equation for calculating the average speed of a moving object is:

• Average speed considers the total distance moved and the total time taken

Average speed formula triangle

Formula triangle for average speed, distance moved and time taken

How to use formula triangles

• Formula triangles are really useful for knowing how to rearrange physics equations

• To use them:

1. Cover up the quantity to be calculated, this is known as the 'subject' of the equation

2. Look at the position of the other two quantities

   • If they are on the same line, this means they are multiplied

   • If one quantity is above the other, this means they are divided - make sure to keep the order of which is on the top and bottom of the fraction!

• In the example below, to calculate average speed, cover-up the variable speed so that only distance and time are left

  • The equation is revealed as:

To use a formula triangle, simply cover up the quantity you wish to calculate, and the structure of the equation is revealed