## Cartesian Diver

The cartesian diver is a hollow cylinder clear tube sealed at one end. The diver is place
in the 2 liter pop bottle with a small amount of air in it. The open end of the diver is
on the bottom. The 2 liter pop bottle is sealed without any air remaining at the top.
With this demo we tested to see if the students comprehended the ideas of buoyancy and
incompressibility of a fluid. We showed them the cartesian diver in the 2 liter pop
bottle and asked to explain why the diver sank when the bottle was squeezed.

The water is incompressible where as the air is not. As the bottle is squeezed, the
pressure inside increases and therefore the volume inside must decrease. (PV=nRT) The
only place where this can occur is in the air inside the cartesian diver. The air
compresses and more water enters into the cartesian diver causing the diver to sink.

Students from grades 5-7 were answering correctly. (Without formulas) We found this
very rewarding since this was one of the demonstrations used at the
Physics Olympics this year!!!!!!

ToLaminar and Turbulent Flow

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