Taking out a stone from the PET bottle

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• A stone is allowed to sink to the bottom of a PET bottle filled with water. We need to remove the stone while spilling the least amount of water. We will need a plastic plate (a thin one, 0.5 mm thick in the video).
• Cut the PET bottle into two parts, horizontally, in advance, and place the stone inside and connect it with Cello tape.
• While tearing off the Cello tape, insert the plastic plate.
• When the plastic plate is completely inserted and the two parts are separated, remove the top part. At this time, the fact that the water inside does not spill follows the same principle as that in the previously published “Water that Won’t Fall”.
• Meanwhile, the pressure of the water in the gap between the PET bottle and plastic plate becomes atmospheric pressure. The pressure of the water at this height is almost the atmospheric pressure, and the pressure above this becomes lower than atmospheric pressure and is balanced.
• The pressure difference between the top and the bottom parts becomes equal to the density of water × gravitational acceleration × height; this pressure difference supports the weight of the water inside. Therefore, no water will spill.
• Remove the stone from the lower part and refill with water.
• Place the top part back and stick the vinyl tape while shifting the plastic plate. Once you have stuck the vinyl tape around the bottle, you are done.

[Keywords]	Depth and pressure, Surface tension
[Related items]	Water that Won’t Fall, Taking out the object that lies at the bottom 2
[Reference]	“The Wonders of Flow”, Japan Society of Mechanical Engineering, Kodansha Blue Backs, P38－41 and P62-67. “Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natsume Publishing, P18-19 and P48-49.

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