Moving Particles on the Water Surface

Let's take a look!

Watch the video on YouTube.

What type of experiment is this?

Experimental procedure and explanation:

• As shown in the experiment video, boards are floated on the surface of the water to divide the water surface into right and left sides.
• Numerous small styrofoam balls are then floated on the water between the boards. The objects that are floated may also be paper cut into small pieces.
• When one drop of a neutral detergent is dripped onto the surface of the water on the right side, the small balls move to the left on the water surface.
• This experiment is able to be performed due to the action of surface tension. The surface tension is weakened at the location where the neutral detergent was dripped, and the styrofoam balls are pulled by the stronger surface tension in the surrounding area and are rapidly spread to the perimeter.
• Through this flow, the water surface between the boards flows to the left and the styrofoam particles also move.

[Keywords]	surface tension
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[Reference]	Logergist “Physics Promenade (Zoku Butsuri no Sanpochimi),” Iwanami Shoten, pp. 58–66. The Japan Society of Mechanical Engineers, “The Wonders of Flow (Nagare no Fushigi),” Kodansha Blue Backs, pp. 62–67. Ryozo Ishiwata, “Illustrated Fluid Dynamics Trivia (Zukai Zatsugaku Ryutai Rikigaku),” Natsume Co., Ltd., pp. 48–49.