Water Fountain 4 (Cartesian Diver)

Let's take a look!

Watch the video on YouTube.

What kind of experiment is this?

Experimental procedure and explanation:

• A phenomenon similar to that of a water fountain can also be observed with a “Cartesian diver,” a toy that can float and sink.
• When you squeeze the PET bottle, the float inside it sinks, and as you release the bottle, the float moves upward. If you initially squeeze the bottle vigorously, a phenomenon similar to that of a water fountain occurs inside the float.
• When the PET bottle is squeezed, the water pressure in the bottle increases. As a result, the pressure inside the float becomes lower than the water pressure around the float, and the surrounding water is pushed into the float due to this pressure difference. If you momentarily squeeze the bottle firmly at this time, a water fountain is created by the momentum of the water that is pushed inward.
• In other words, a water fountain is created by the pressure difference between the upstream (surrounding water) and downstream (inside the float) sides of the water fountain.

[Keywords]	pressure, buoyancy
[Related items]	Cartesian Diver
[Reference]	“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, pp.42-47 “Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natume Publishing, pp.14-15 and 192-193