Ok, so I'm not sure if this is the correct place to ask this, but I'll ask anyway.
I have been asked to find out the angle at which a water droplet will start rolling on an injection moulded surface of PP (Polypropylene) plastic.
the only force acting on the droplet is gravity and it's own surface tension
there is no air flow over the drop
What i know so far...
- PP (Polypropylene) plastic is somewhat a hydrophillic surface which means the contact angle of a droplet is less than 90 deg
This sugests that if the plastic was tilted to an angle of 90 degress the water droplet would still not run off.
What is confusing me is the addition of the mass/volume of the water droplet and at what mass/voulme would the droplet need to be for it to start rolling at a specific angle.
Any help will be very much appreciated!
Alex
