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Year 9 - Science

Gravitational force and weight

Hidden forces

Unit Summary

This unit explores forces, deformation, Hooke's Law, moments, and work done. It covers pressure in liquids, atmospheric pressure, upthrust, and equilibrium, as well as simple machines and force-extension relationships, highlighting how forces affect motion, friction, and object deformation.

Lesson Summary

You will learn to describe and apply the relationship between mass and gravitational force.

Key Notes

  • The mass of an object is measured in kilograms.
  • A force of about 10 N is needed to lift 1 kg on Earth.
  • On Earth, a 1 kg mass pushes down on a surface with a force of about 10 N.
  • There are 1000 g in 1 kg.
  • Gravitational force, W = m × g

Vocabulary To Learn

  • gravitational force: The force that acts on an object inside a gravitational field.
  • mass: The amount of matter (material) in an object.
  • gravitational field strength: The force per kilogram caused by a gravitational field.
  • newton (N): The unit for force.
  • newtons per kilogram (N/kg): The unit for gravitational field strength.

Common Mistakes To Avoid

  • Pupils often mix up the terms for weight and mass and use weight when they mean mass and vice versa.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

The mass of an object is measured in kilograms. A force of about 10 N is needed to lift 1 kg on Earth.

2. Define this scientific word and use it in context. 'gravitational force'

The force that acts on an object inside a gravitational field. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: Pupils often mix up the terms for weight and mass and use weight when they mean mass and vice versa. Correction: Teach pupils that a force lifts objects against the pull of gravity before introducing the term weight.

More Lessons In This Unit

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