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NotScientific · Feb 25, 2004, 08:32 am

Do you know what happens when a drop of water hits a non-absorbent surface? Yeah you’re right (if you don’t have the answer, please re-read the title of this column), the drop bounces upwards.

A French scientific team from the Collçge de France have studied the scene carefully with a camera that took 40000 images per second. Here are the results:
At first, when it hits the surface, the drop flattens. Then, it bounces up due to the movement energy it had when falling down. The drop will continue going upwards eventually taking the shape of a needle. Afterwards, the drop falls upon itself, into itself. It thus takes the shape of a pancake (again) but this time, the drop is in midair.

This phenomenon is different to a drop falling on other surfaces as in this case, the drop crashes on the surface leaving only a small quantity of the water to bounce up.
Physicists have also found out that the actual speed of a drop influences its deformation but not the time taken for it to get in contact with the surface. This actually depends upon the mass of the drop.

Anyway why is all this stuff important anyway? Scientists believe that this find may be of interest to the industry. There’s a small illustration:
Imagine not seeing droplets of rain on your car’s windscreen when it is in fact raining cats and dogs outside. Cool, isn’t it? Well this may well be possible with these new data obtained by the scientists from the Collçge de France. How though? Easy enough! The period of contact of the raindrops with the windscreen is so minimal that the driver does not even see them!

Water drops bounces like springs, would you ever have thought of this? No, I’m not sure you would.

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That's the second article in what I hope will be a long time running column named 'Not Scientific Science'
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This column also appeared at BackWash.com

Feb 25, 2004, 08:32 am	#1 (permalink) (top)
NotScientific Molten Ash Location: Mauritius Posts: 35	Do you know what happens when a drop of water hits a non-absorbent surface? Yeah you’re right (if you don’t have the answer, please re-read the title of this column), the drop bounces upwards. A French scientific team from the Collçge de France have studied the scene carefully with a camera that took 40000 images per second. Here are the results: At first, when it hits the surface, the drop flattens. Then, it bounces up due to the movement energy it had when falling down. The drop will continue going upwards eventually taking the shape of a needle. Afterwards, the drop falls upon itself, into itself. It thus takes the shape of a pancake (again) but this time, the drop is in midair. This phenomenon is different to a drop falling on other surfaces as in this case, the drop crashes on the surface leaving only a small quantity of the water to bounce up. Physicists have also found out that the actual speed of a drop influences its deformation but not the time taken for it to get in contact with the surface. This actually depends upon the mass of the drop. Anyway why is all this stuff important anyway? Scientists believe that this find may be of interest to the industry. There’s a small illustration: Imagine not seeing droplets of rain on your car’s windscreen when it is in fact raining cats and dogs outside. Cool, isn’t it? Well this may well be possible with these new data obtained by the scientists from the Collçge de France. How though? Easy enough! The period of contact of the raindrops with the windscreen is so minimal that the driver does not even see them! Water drops bounces like springs, would you ever have thought of this? No, I’m not sure you would. ____________________________________________________________________________ That's the second article in what I hope will be a long time running column named 'Not Scientific Science' ____________________________________________________________________________ This column also appeared at BackWash.com I'm Columnist here at Volconvo.com and also at BackWash.com. Check my columns in the Science forum then.