Monday, 18 May 2009

Hanky Umbrella Experiment

A very fun experiment. We felt like magicians as we tipped the glass upside down without the water falling out. (Well, only a smidgen dripped through, but we knew that was supposed to happen.)

Nothing hidden in the hanky ...
Place hanky over glass
Twist tightly underneath glass
Then hey presto! Tip glass over and the water stays in the glass

This photo is from our first attempt the night before, but it was one of those "oh no!!" moments ... the batteries went flat at the crucial point of the experiment! lol
So ... how did we do it?

Aah, a magician doesn't give away his secret!!

Just as well we're not magicians then huh!?

Surface Tension

Water has a property called surface tension
. Although it looks like liquid, water has a kind of elastic skin and the surface tension creates a barrier.

But what relevance has that to the hanky? Well, the trick (or should we call it the first step in the experiment) is to soak the handkerchief in water and squeeze it out.

The hanky has little tiny weaves in it and little places where water can get trapped. By stretching it really tight the surface tension stretches out and stops the water from pouring out of the glass.

The same principle applies to the use of umbrellas. Surface tension. That's why we don't get wet.

If you do try this experiment, be rest assured that you will lose a small amount of water initially ... after all, a handkerchief isn't as strong as an umbrella eh? But it certainly gets the point across that if water didn't have surface tension, then water wouldn't be water!

A few more experiments to come still, so tune back in soon.

Thanks for dropping by
ka kite ano

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