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Cartesian Diver


Consists of a 2L soda bottle with an eye dropper inside. The eye dropper contains a small air bubble and is open on the bottom end.


Demonstrates the effect of density on buoyancy as well as the ideal gas law.


  • Cartesian Diver Bottle


Prior to running the demo you'll want to check that the dropper is roughly neutrally buoyant. The dropper isn't entirely waterproof so overtime the air bubble inside may escape. To re-balance it, you'll want to take it out, fill it with air, and gradually squeeze the air out while submerged until it barely floats.

To run this demo, simply place it where the students can see it and give the bottle a squeeze from the sides. Doing so will increase the pressure within the bottle, which (by the ideal gas law) will decrease the volume of the trapped air bubble. As the bubble gets smaller water moves in to fill the gap left, and the Cartesian diver will sink as it's density increases.


There are also a couple glass 'divers' available in the demo room. They are pictured below. They work much the same as the eye dropper (and possibly are better) but they're not immediately familiar objects like the dropper is.

Demo room information

Location C1, glass version C3
Maker Unknown
Current State Working
demonstrations/2_fluid_mechanics/2b_statics_of_fluids/cartesian_diver/start.txt · Last modified: 2020/02/03 21:50 by demoroom