Monday, November 13, 2006

Fun with Physics

Fun with non-Newtonian fluids.

The basic idea is that in fluids, adjacent particles can swap places instantaneously, so the fluid can flow. In solids, adjacent particles can't swap places, so they can't flow.

However, that's actually just an ideal. All fluids take a finite amount of time for the particles to swap places, and many solids can have the particles swapping places, just they take a long time for it to happen.

So "solid" lead or glass will flow, if you give it long enough, and if you do stuff quickly enough to water, the particles won't have a chance to flow and it will behave more like a solid.

Another way of seeing the effects is to do what they do here - use a thick suspension of cornflour in water. Because the particles are big, they are very slow to swap places compared to most fluids, but still quicker than solids. So if you do stuff to the suspension very quickly, the particles won't have time to swap places and it'll behave like a solid. But if you do stuff to it very slowly, the particles will have time to swap places and it'll behave like a liquid. The results are as seen in the video...

8 comments:

Anonymous said...

WOW! That's so cool! : D

dmurane said...

awesome...could it be possible to have those tricks in my bathroom?? or it`s necessary to have more than 2 cubic metres of water?

Custard said...

Yeah - should be possible.

You'd need a huge amount of cornflour / cornstarch / custard powder though, and it would be difficult to get the ratios exactly right.

dmurane said...

ok! So i`ll try that out, and will let You know how did it go...
ohh, and ratious (no I idea what is that) should not be a problem, I think!

Custard said...

The issue with ratios is that if you get too much water, it's far too runny and won't support your weight. If there's too little, it becomes crumbly.

When you're working with tiny quantities, it's fairly easy to get the balance once you know what you're doing...

HJ said...

Think carefully about how you're going to clean your bath afterwards though! Several gallons of cornstarch down the drain will not do good things to your pipes!

dmurane said...

is this also one of the kind? http://youtube.com/watch?v=qnYKa2n47-4

Custard said...

no - that's a visual illusion done using perspex - see the comments on the video...