Physics KS3/KS4: An introduction to the speed equation

In this short video Professor Brian Cox gives an introduction to speed. He defines what is meant by speed and how to calculate speed by applying the 'distance divided by time' equation.

The calculation is explained in the context of a familiar journey from home to school and illustrates the logic of the speed equation.

The use of the correct units is clear (metres per minute in this example) and the calculated speed is contextualised in the example of a fast walk or jog, which will be familiar to students and will allow them to sense-check their answers.

Teacher Notes

Points for discussion:
This video provides a simple introduction to the scalar quantity of speed as distance divided by time and so is useful at KS3 in the first instance.

The modelling of logic in this video is also useful more widely as it demonstrates to students that we can often sense-check an equation or a calculated value.

Suggested activities:
This video could be used as part of an introduction to speed at KS3 as it highlights the logic of the speed calculation. Students often fail to apply logic to simple equations and move straight to rote learning.

After watching the video, students could be given other simple calculations to attempt, including using different units. This could highlight the importance of using correct units by comparing, for example, 10m/min to 10m/s. Students could then progress to changing the subject of the equation.

The video could also be used to stimulate discussion about some typical speeds, such as those when running, driving, or cycling, providing an opportunity to apply their knowledge to other real life contexts.

A good follow-on from this could be clip 4 in this series, which focuses on the importance of sense-checking mathematical answers.

At KS4, this video could be used as a simple revision of speed, a scalar quantity, before moving on to learning about velocity, a vector quantity.

Curriculum Notes

Suitable for KS3, Combined Science and Physics GCSE in England, Wales and Northern Ireland and at National 4 and 5 in Scotland.

More from this series:

Newton’s First Law
Hooke’s Law
The importance of checking mathematical answers
Average speed
Relative speed