# Project which involve a falling water droplet

1. Apr 7, 2006

### blue_moon

I am working on this project which involve a falling water droplet on both dry and wet surfaces to figure out how is the splash is going to affect the water separation however, I have to find out the droplet size providing this info

1) Needle diameter
2) Water tension

please help , if there is any derivation or formula that includes the tension and the needle diameter or whatever would help solving this problem?

Blue

2. Apr 7, 2006

### Astronuc

Staff Emeritus
Last edited by a moderator: May 2, 2017
3. Apr 8, 2006

### blue_moon

I founf this I am stuck I have no Idea how to get the droplet size or diameter from the relation below :

for the droplet to detach from the needle tip, gravity has to overcome the surface
tension. so when mg exceeds the interfacial tension at the release point the drop will
fall.
the interfacial tension is: surface tension x 2*pi*r where r is the needle radius.
Water at 20°C has a surface tension of 72.8 dynes/cm...