Viscosity
Applied Science: BTEC Level 3 National Extended Diploma, topic 4.11.2
Viscosity
An important property of fluids is their viscosity.
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.
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.
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.
Stokes' law
- Stokes' law states that the viscous drag will be given by the equation:
- .
- is the viscous drag.
- is the viscosity of the fluid.
- is the radius of the moving object.
- is the velocity of the moving object.
Limitations of Stokes' law
- Stokes' law only applies to slow-moving and small objects.
- Stokes' law also assumes that the object is perfectly spherical.
Test yourself on Viscosity
Which of the following has the lowest viscosity?
What kind of a force is the viscous drag?
Stokes' law assumes that objects are what shape?