Science at key stage 3 (Year 9)
Unit 9J: Gravity and space
Section 1: What is gravity?
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Objectives |
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- that gravity is an attractive force which acts on the Earth towards the centre of the planet
- that gravity is an attractive force between objects with mass
- about how the idea of gravity was related to empirical observations
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Activities |
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Outcomes |
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Children: |
- Remind pupils of the distinction between mass and weight and that weight is the force due to gravity. Present pupils with a picture of the Earth and ask them to indicate what would happen to a ball dropped at different positions. Establish that the ball would fall towards the Earth and that this is the definition of 'downwards'. Generalise that gravity is an attractive force between any masses, but that we feel its pull only with very large masses, such as the Earth.
- Use the historical association of the newton to highlight that the concept of gravity was a very difficult one for scientists to understand. Explain that while Newton did not 'discover' gravity, he formulated the concept mathematically and realised its importance, at levels ranging from apples falling from trees to the orbits of planets. Drop an apple into pupils' hands to feel the gravitational force of 1 newton. Ask pupils to lift masses of a known value and feel the attractive force of the Earth's gravity pulling them back.
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- state that a ball dropped anywhere on the Earth will fall towards the centre of the planet, due to the attractive gravitational force between masses
- use the idea of gravity to explain a range of observations both familiar and novel
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Points to note |
- It is important for pupils to realise that gravity is associated with physical bodies, and not with a concept of 'down-ness'.
- Whilst there is some doubt over the accuracy of the story involving the falling apple, it is one which pupils may know and be interested in. It is a curious coincidence that the force of gravity on an average apple is about 1 newton.
- Pupils could use the value of the gravitational field strength of the Earth (10 N kg-1) to work out the force in newtons on different masses (relates to unit 7K 'Forces and their effects').
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This unit is divided into sections. Each section contains a sequence of
activities with related objectives and outcomes. You can view this unit by
moving through the sections or print/download the whole unit.
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