# Bernoulli Tubes

#### Abstract

The height of the fluids in the tubes indicates that pressure is highest where the fluid is moving fastest.

The photo at right shows the Bernoulli Tubes apparatus. The red liquid is pushed down further when the pressure is higher. Download video below.

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#### Principles Illustrated

Bernoulli Principle. See additional notes below.

#### Powerpoint

Powerpoint for use with this demonstration (right-click and “save link as”): Fluid_Demos.ppt

Extension

#### Instructions

We have two versions. A large version for lecture theaters that operates on air, and a smaller version for classrooms and labs that can operate with either air or water.

The air flow has to be adjusted and it helps to put fairly long hoses on each end of the apparatus.

#### Safety

The larger version is somewhat delicate as it has not been annealed. Handle with more than usual care.

Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.

#### Notes

Bernoulli’s principle tells us that the pressure is lowest in a fluid where the fluid is moving fastest (for points at the same height). This is reflected in Bernoulli’s equation for an incompressible fluid.

Where the fluid is moving fastest, in the smallest diameter tube, the pressure should be lowest.

The Bernoulli equation is exact only under restricted conditions and will apply only approximately to air flow in these experiments. However, the observed pressures are in the correct order: largest in the large diameter tube and smallest in the small diameter tube.

#### Related Resources

• Bernoulli plates
• Floating Ball
• Funnel Ball

#### Teaching Resources

Would you like to contribute lesson suggestions? Contact us.

PIRA 2C20.10

#### Credits

This teaching resource was developed with support from