Water Droplets Gliding on the Surface of Water

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Watch the video on YouTube.

What type of experiment is this?

Experimental procedure and explanation:

• Fill a teacup with water until the water surface swells above the rim of the cup.
• Next, drop drips of water onto the water surface. When the height from which the water is dripped is properly adjusted and the water is skillfully dripped, a phenomenon can be observed in which the water droplets glide across the water surface.
• This experiment is introduced in the “No. 5 Path to Physics” by the Logergist group. Water can also be dripped from a water faucet rather than using a dropper. However, the water must be pure water without any oil or such substance floating in it.
• Water droplets become nearly spherical due to surface tension. However, when the water droplets start to glide across the water surface, a film of air is maintained between the droplet of water and the water surface; thus, this type of phenomenon occurs.
• When the water droplet contacts the water surface, it will either integrate with the water and disappear or will become a small water droplet that springs upward because of the force at which it was dropped. Moreover, that water droplet may glide across the surface of the water. Furthermore, if waves are formed on the water surface, water droplets may smoothly glide because of the interference with those waves, but the details of this cannot be confirmed.

[Keywords]	surface tension
[Related items]	Swelled Water Surface
[Reference]	Logergist “No. 5: Physics Promenade (Daigo: Butsuri no Sanpochimi),” Iwanami Shoten, pp. 79–94. (Logergist is a name given to a group of seven physicists including Professor Isao Imai. Moreover, in the five volumes of “Physics Promenade,” various physical phenomenon and daily events are considered.) 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 Publishing, pp. 48–49.