Contextualisation

Stevin's Law, also known as Stevin's theorem, is a cornerstone of fluid physics. Proposed by the Belgian scientist Simon Stevin in the 16th century, this theorem is crucial for understanding the behaviour of pressure in fluids at rest.

Stevin's Law can be summarized by the following expression: the pressure difference between two points in an incompressible and static fluid is equal to the product of the density (ρ), the acceleration due to gravity (g), and the height difference (h) between the two points. In formula form, we have: ΔP = ρ.g.h.

It may seem a bit abstract, but a clear understanding of this principle is fundamental to understanding a variety of everyday phenomena. For example, it explains why the pressure in our ears increases when we dive to the bottom of a swimming pool or the sea.

From a practical applications perspective, Stevin's Law has implications in many areas of engineering, medicine, and biology. In civil engineering, for example, it is used to calculate the pressures acting on the walls of a water reservoir or a dam. In medicine, it gives us an understanding of how blood flows in our blood vessels, carrying nutrients to all parts of the body.

If you want to delve deeper into Stevin's Law, I suggest reading the book "Physics for Exact and Earth Sciences" by Frederico Borges de Morais and Luciene Lima dos Reis. You can also watch the video "Stevin's Law" from the "The Pocket Physicist" channel on YouTube for a more visual explanation of the topic.

Hands-on Activity

Activity title: Simulating Stevin's Law

Project goal:

Through a simple and fun experimental activity, students will explore Stevin's Law and see in practice how the pressure of a fluid changes with depth.

Project description:

Students will create a simple model of a fluid at rest (water in a transparent container) and will measure the pressure at different depths using a homemade manometer. Students will record their observations, analyse the results and write a report based on their findings.

Materials needed:

• Transparent container (minimum height of 30cm)
• Water
• Food colouring
• 2 plastic straws
• Tape
• Ruler
• Liquid silicone rubber (optional)

Step by Step:

1. Fill the container with water to 3/4 of its capacity.

2. Add a few drops of food colouring to the water to improve visualisation.

3. Make a homemade manometer: Take two plastic straws and join them with tape, forming a single longer tube. Seal one end with liquid silicone rubber or another waterproof and sealant material.

4. Slowly and gently submerge the unsealed end of the straw into the water. Make sure that the straw is vertical.

5. Mark the heights of 10cm, 20cm and 30cm on the container from the surface of the water.

6. Observe the water level inside the straw when it is placed at each of the height markings. Take pictures or make drawings to record.

7. Note the height of the water in the straw for each height marking on the container. This will be the value of the pressure at the different points in the fluid.

After carrying out the experiment, the groups will analyse the results and discuss their observations. Students should make direct links between what they observed in the experiment and Stevin's Law.

Final Product and Evaluation Criteria

Students must produce a written document, in report format, about the activity. The report should be divided into four main sections: Introduction, Development, Conclusions and Bibliography.

In the Introduction, students will present Stevin's Law, its relevance, and the objective of the project.

In the Development, students will explain Stevin's Law, the experiment in detail, the methodology of the experiment and how the experiment relates to Stevin's Law. In addition, students must present the results obtained and discuss them.

In the Conclusion, students will summarise the main points, discuss what they learned from carrying out the project and what conclusions were drawn.

In the Bibliography, students will list their sources of information, such as books, websites, videos, etc.

Each of these items will be assessed considering the understanding of the theory, the clarity in presenting the practical activity and the discussion of the results. The evaluation will also take into account teamwork, organisation and punctuality in delivering the report.