Year 9 - Science
Floating, mass and shape
Hidden forces
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
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 explain how the density of an object determines how well it floats.
Key Notes
- The whole of an object is floating on water if part of it is above the surface.
- How well an object floats in a liquid does not depend on the depth of the liquid.
- An object floats in water if its shape can push its own mass of water out of the way without going under.
Vocabulary To Learn
- upthrust: A force acting upwards due to pressure is an upthrust.
- displaced: Water is displaced (moved) when an object floats on it or sinks in it.
- displacement can: A displacement can is used to find the volume of water displaced by objects when they float or sink.
- density: If the density of an object is less than the density of water, it will float.
Common Mistakes To Avoid
- Pupils may think that all light objects float and that all heavy objects sink.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
The whole of an object is floating on water if part of it is above the surface. How well an object floats in a liquid does not depend on the depth of the liquid.
2. Define this scientific word and use it in context. 'upthrust'
A force acting upwards due to pressure is an upthrust. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: Pupils may think that all light objects float and that all heavy objects sink. Correction: Explore how mass and volume (determined by shape) affect whether objects float or sink - before discussing density.
More Lessons In This Unit
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