Buoyancy & Pressure in Fluids: Soda Bottle Cartesian Diver
Students observe Pascal's law, Archimedes' principle and the ideal gas law as a Cartesian diver moves within a closed system. The Cartesian diver is neutrally buoyant and begins to sink when an external pressure is applied to the closed system. A basic explanation and proof of this process is provided in this activity, and supplementary ideas for more extensive demonstrations and independent group activities are presented.
French philosopher and mathematician René Descartes (left). A Cartesian devil diver toy made in Germany.Copyright (left) Unknown artist, Wikimedia Commons; (right) 2006 Hannes Grobe, Wikimedia Commons
http://commons.wikimedia.org/wiki/File:Ren%C3%A9_Descartes.jpg
http://commons.wikimedia.org/wiki/File:Cartesian_devil_hg.jpg
The concepts of Pascal's law, Archimedes' principle, the ideal gas law and the density-buoyancy relationship are important in science, engineering and technology applications such as fish physiology, scuba diving and various submersibles. Most boney fish have a swim bladder that enables them to control their buoyancy, or height in the water column, without swimming. Scuba divers use special equipment such as weighting systems, diving suits and buoyancy compensators to control their buoyancy. Submersibles enable the exploration of depths much greater than can be reached via satellite and shipboard technologies; these creative submersible and remotely operated vehicle (ROV) inventions are necessary for researchers to explore very deep ocean communities and discover new species.
After this activity, students should be able to:
- Use a Cartesian diver and interpret how it works by using terminology such as density, buoyancy and pressure.
- Explain the physics of the Cartesian diver behavior based on an understanding of Pascal's law and Archimedes' principle.