4.11.2

Viscosity

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Viscosity

An important property of fluids is their viscosity.

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Viscosity

  • The viscosity of a fluid measures how resistant the fluid is to moving or being deformed.
  • Orange juice has a low viscosity as it flows easily when you pour it into a glass.
  • Golden syrup has a high viscosity as it flows slowly when you pour it over pancakes.
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Viscous drag

  • Viscous drag is the frictional force you feel as you move through a fluid.
    • For objects moving in the air, this is called air resistance.
    • Viscous drag is what makes trying to run in a swimming pool so difficult.

Stokes' Law

Stokes' Law describes viscous drag.

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Viscous drag

  • Viscosity is the measure of how thick a fluid is.
  • When an object is moved through a viscous fluid, it will experience a resistive force known as viscous drag.
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Stokes' law

  • Stokes' law states that the viscous drag will be given by the equation:
    • F=6πηrv F = 6 \pi \eta r v .
    • FF is the viscous drag.
    • η\eta is the viscosity of the fluid.
    • rr is the radius of the moving object.
    • vv is the velocity of the moving object.
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Limitations of Stokes' law

  • Stokes' law only applies to slow-moving and small objects.
  • Stokes' law also assumes that the object is perfectly spherical.

Jump to other topics

1Principles of Science I

1.1Structure & Bonding

1.2Properties of Substances

1.3Cell Structure & Function

1.4Cell Specialisation

1.5Tissue Structure & Function

1.6Working with Waves

1.7Waves in Communication

2Practical Scientific Procedures and Techniques

3Science Investigation Skills

4Principles of Science II

4.1Extracting Elements

4.2Relating Properties to use of Substances

4.3Organic Chemistry

4.4Energy Changes in Industry

4.5The Circulatory System

4.6Ventilation & Gas Exchange

4.7Urinary System

4.8Cell Transport

4.9Thermal Physics

4.10Materials

4.11Fluids

5Contemporary Issues in Science

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