Saturday, 13 October 2012

Bouncing Water Droplet

Still amazed on what you can do with a high speed camera, water and a needle.  Noah Philips shows that water droplets bounce.  Surface tension is amazing....


  1. I don't get it. How does it bounce?

  2. What is happening here you ask? Like the name of the blog suggests this is a demonstration of surface tension at its finest. Water molecules have a surface tension of 72 dynes arising from the oxygen binding to two hydrogens through hydrogen bonds. The structure of water has a partial positive charge on one end and a partial negative charge on the other. As molecules slip past each other in a liquid state, they form weak bonds known as hydrogen bonds.

    On the surface of the water hydrogen bonds are more prevalent because they are more restricted. So the water in air forms balls (this is even more present absence of gravity like space). The bouncing effect seen in the video is a result of the drops having enough of their own surface tension to bounce off surface of the water like a basketball hitting another basketball. However, in this case it is fluid and about half of the water gets tossed back up in the air as a droplet. This phenomenon has a name — it’s called the coalescence cascade (1). It would be interesting to change the surface tension of either of the fluids to see different drop sizes bouncing and coalescing.