Physics KS3 / GCSE: What is Newton's Canon and Third Law?

Dr Kevin Fong uses two children from the audience to help to demonstrate Newton’s suggestion that if you can throw a projectile fast enough and far enough, it will end up travelling around the Earth in orbit.

This is known as Newton's Third Law.

This theory was recorded in his famous publication ‘Principia’, and the curator of the Royal Institute's archives, Charlotte New, shows the audience a second edition of one of the volumes of it.

Kevin then demonstrates Newton's Third Law using fire extinguishers to propel himself on a trolley and explains how this is linked to rocket propulsion.

This clip is from the Royal Institution Christmas Lectures 2015.

Teacher Notes

This clip could be used to introduce the topic of space travel and the effect of gravity and other forces.

Newton’s Third Law and its application to rocket propulsion could be demonstrated by allowing students to blow up balloons and release them, or by using a water powered rocket.

Curriculum Notes

This clip will be relevant for teaching GCSE Physics.

This topic appears in OCR, Edexcel, AQA, WJEC KS4/GCSE in England and Wales, CCEA GCSE in Northern Ireland and SQA National 4/5 in Scotland.

More from the Royal Institution Christmas Lectures 2015

Using Earth’s rotation to launch a rocket
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How the vacuum of space effects the human body
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Resonant Frequency
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Orbital Rendezvous
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What does gas weigh?
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Why are bones weaker in orbit?
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How micro-gravity disorientates us
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The danger of orbital debris
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Demonstrating heat shield material
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Why Earth rock is found on the Moon
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Demonstrating radiation detectors
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How Earth protects us from radiation
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Why tardigrades can survive in orbit
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How to recycle urine in space
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