5.4.4

Pressure Changes

Test yourself

Floating and Upthrust

A partially submerged object (an object that’s not fully in a liquid) will experience greater pressure on the bottom surface than on the top surface. This creates a resultant force upwards. We call this force upthrust.

Illustrative background for Upthrust = weight of liquid displacedIllustrative background for Upthrust = weight of liquid displaced ?? "content

Upthrust = weight of liquid displaced

  • The upthrust that acts on an object is equal to the weight of the liquid that has been forced away (displaced) by that object.
Illustrative background for FloatingIllustrative background for Floating ?? "content

Floating

  • If the object’s weight is equal to the upthrust, then the forces balance and the object will float in the liquid.
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Sinking

  • If the object’s weight is greater than the upthrust, then the object will sink.

Depth Control of Submarine

Submarines use the balance between upthrust and weight to control their depth in water.

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Sinking

  • When a submarine wants to sink, it fills its tanks with water to increase its weight.
  • This means the submarine’s weight is greater than the upthrust and it sinks.
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Rising

  • When a submarine wants to come up to the surface, it fills its tanks with compressed air to reduce its weight.
  • Weight becomes less than upthrust so the submarine rises.

Jump to other topics

1Energy

1.1Energy Changes

1.1.1Energy Stores

1.1.2Calculating Changes in Energy

1.1.3Changes in Kinetic Energy - Calculations

1.1.4Changes in GPE - Calculations

1.1.5Changes in EPE - Calculations

1.1.6Energy Transfers

1.1.7Mechanical Work Done

1.1.8Mechanical Work - Calculations

1.1.9Electrical Work Done

1.1.10Electrical Work Done- Calculations

1.2Energy Losses & Efficiency

1.2.1Energy Losses & Efficiency

1.2.2Energy Losses & Efficiency 2

1.2.3Efficiency - Calculations

1.2.4Grade 9 - Energy & Efficiency

1.3Energy Resources

1.3.1Fossil Fuels & Geothermal Energy

1.3.2Wind & Water Energy Sources

1.3.3Nuclear & Solar Energy

1.3.4Sustainability

1.3.5Renewable Energy

1.3.6End of Topic Test - Energy

1.3.7Exam-Style Questions - Energy

2Electricity

2.1Electric Charge

2.1.1Circuit Diagrams & Components

2.1.2Current

2.1.3Current - Calculations

2.1.4Conductors

2.1.5Potential Difference

2.1.6Voltage - Calculations

2.2Resistance & Electrical Work

2.2.1Resistance

2.2.2Diodes, LDRs & Thermistors

2.2.3Electrical Work

2.2.4Ohm's Law

2.2.5Resistance and Ohms Law - Calculations

2.2.6Electrical Work - Calculations

2.3Electric Circuits

2.3.1Series Circuits

2.3.2Series Circuits 2

2.3.3Series Circuits - Calculations

2.3.4Parallel Circuits

2.3.5Parallel Circuits 2

2.3.6Parallel Circuits - Calculations

2.3.7Grade 9 - Circuits

2.3.8Exam-Style Questions - Electricity

2.4Electricity in Homes

2.4.1Domestic Uses

2.4.2Domestic Uses 2

2.4.3Domestic Uses - Calculations

2.4.4Electrical Safety

2.4.5Electrical Safety 2

2.4.6End of Topic Test - Electricity

2.5Static Electricity

2.5.1Static Electricity

2.5.2Static Electricity 2

3Particle Model of Matter

3.1States of Matter

3.1.1Atomic Structure

3.1.2Atomic Structure 2

3.1.3Density

3.1.4Density - Calculations

3.1.5Changes of State

3.1.6Exam-Style Questions - Density

3.2Heat

3.2.1Internal Energy

3.2.2Heat Capacities

3.2.3Internal Energy - Calculations

3.2.4Latent Heat

3.2.5Latent Heat - Calculations

3.2.6Latent Heat Experiments

3.3Particle Motion in Gases

3.3.1Particle Motion in Gases

3.3.2Particle Motion in Gases 2

3.3.3End of Topic Test - Particle Model of Matter

3.3.4Grade 9 - Particle Model of Matter

3.3.5Exam-Style Questions - Specific Heat Capacity

4Atoms & Radiation

4.1Atoms

4.1.1Atomic Model

4.1.2Atomic Model 2

4.1.3Atoms & Ions

4.1.4Isotopes

4.1.5Exam-Style Questions - Atomic Structure

4.2Radiation

4.2.1Radioactive Decay

4.2.2Radioactive Decay 2

4.2.3Types of Radioactive Emission

4.2.4Fission & Fusion

4.2.5Radioactive Decay Equations

4.2.6Radio. decay equations - Calculations

4.2.7Half Lives & Ionising Radiation

4.2.8Half Life - Calculations

4.2.9Uses & Dangers of Radiation

4.2.10Uses & Dangers of Radiation 2

4.2.11End of Topic Test - Atoms & Radiation

4.2.12Grade 9 - Radiation

4.2.13Exam-Style Questions - Radioactive Decay

5Forces

5.1Basics of Motion

5.1.1Basics of Motion

5.1.2Basics of Motion 2

5.1.3Basics of Motion 3

5.1.4Distance- & Speed-Time Graphs

5.1.5Average Speed - Calculations

5.1.6Acceleration - Calculations

5.1.7Uniform Acceleration - Calculations

5.1.8Grade 9 - Motion

5.1.9Exam-Style Questions - Motion

5.2Forces

5.2.1Gravity

5.2.2Gravity - Calculations

5.2.3Resultant Forces

5.2.4Newton Second Law - Calculations

5.2.5Force Diagrams

5.2.6Free Body Diagrams - Calculations

5.2.7Stretching a Spring

5.2.8Hooke's Law

5.2.9Hooke's Law - Calculations

5.2.10Elastic Potential Energy

5.2.11Elastic Potential - Calculations

5.2.12Exam-Style Questions - Elastic Potential Energy

5.3Effects of Forces

5.3.1Acceleration

5.3.2Acceleration 2

5.3.3Momentum

5.3.4Change in Momentum - Calculations

5.3.5Momentum - Calculations

5.3.6Moments

5.3.7Moments - Calculations

5.3.8Circular Motion

5.3.9Levers & Gears

5.3.10Stopping Distance

5.3.11Decelerations

5.3.12Stopping Distance - Calculations

5.4Pressure

5.4.1Pressure

5.4.2Pressure - Calculations

5.4.3Liquid Pressure - Calculations

5.4.4Pressure Changes

5.4.5End of Topic Test - Forces

5.4.6Exam-Style Questions - Pressure

6Waves

6.1Wave Basics

6.1.1Basics & Formula

6.1.2Wave Speed - Calculations

6.1.3Describing Waves

6.1.4Wave Frequency - Calculations

6.1.5Transverse & Longitudinal Waves

6.1.6Required Practical - Ripple Tank

6.2Waves at a Boundary

6.2.1Waves at a Boundary

6.2.2Waves at a Boundary 2

6.3Sound Waves

6.3.1Sound Waves

6.3.2Sound Waves 2

6.3.3Uses of Sound Waves

6.3.4Sound Waves - Calculations

6.3.5End of Topic Test - Introduction to Waves

6.3.6Exam-Style Questions - Wave Speed

6.4Electromagnetic Waves

6.4.1Properties

6.4.2Gamma, X-Ray & UV Light

6.4.3Infrared, Microwave & Radio Waves

6.4.4Properties 2

6.4.5Visible Light

6.4.6Visible Light 2

6.4.7Grade 9 - Waves

6.5Lenses

6.5.1Lenses

6.5.2Lenses - Calculations

6.5.3Images & Ray Diagrams

6.6Heat & Radiation

6.6.1Infrared Radiation

6.6.2Temperature

6.6.3Greenhouse Effect

6.6.4End of Topic Test - EM Waves, Lenses & Heat

6.6.5Exam-Style Questions - EM Radiation

7Magnetism

7.1Magnetism Basics

7.1.1Magnetic Materials

7.1.2Magnetic Fields

7.2Electromagnetism

7.2.1Electromagnetism

7.2.2Electromagnetism 2

7.2.3Motor Effect

7.2.4Magnetic Flux - Calculations

7.2.5Motors

7.2.6Induced Potential

7.2.7Induced Potential 2

7.2.8Generator Effect

7.2.9Generator Effect 2

7.3Transformers

7.3.1Transformers

7.3.2Transformers 2

7.3.3Transformers 3

7.3.4Transformers - Calculations

7.3.5Transformers 2 - Calculations

7.3.6End of Topic Test - Magnetism

7.3.7Grade 9 - Transformers

7.3.8Exam-Style Questions - Magnetic Fields

8Astrophysics

8.1Astrophysics

8.1.1The Solar System

8.1.2The Solar System - Calculations

8.1.3Orbits

8.1.4Orbits HyperLearning

8.1.5Life Cycle of a Star

8.1.6The Universe

8.1.7End of Topic Test - Astrophysics

8.1.8Exam-Style Questions - Astrophysics

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Liquid Pressure - Calculations

End of Topic Test - Forces