Physics KS3/GCSE: Newton's Third Law

Science presenter Jon Chase explains Newton’s third law with the help of some skateboarders.

The skateboarders stand on separate boards and then one of them pushes away from the other one, causing them to both move.

Newton’s second law is also referred to, as the demonstration is repeated with two people standing on one of the boards.

Jon defines Newton’s law as ‘If body A exerts a force on body B, then body B will exert an equal opposite force on body A.’

Teacher Notes

The demonstration with the skateboarders could be repeated in class. The class could then construct water rockets and observe Newton’s third law in action.

They could investigate the optimum ration of water to air volume needed for the highest flight. Include a discussion of fair testing and reliability, as well as issues of how to measure the height.

Curriculum Notes

This short film will be relevant for teaching physics and science in general at KS3 and KS4 in England, Wales and Northern Ireland and National 4/5 in Scotland.

More from Physics Bites:

A demonstration of friction
Falling bodies
Radioactive decay
Refraction of light
Total internal reflection