The theory of quicksand

I think most of you know quicksand is a gooey stuff that grabs a hold of its victim and swallows them alive! So, what is quicksand and how does it really work? I learn this from a teacher and happen to find a website that exactly describing this experiment, therefore to know more info on it just click the link and I think there is a video on it too.

This theory can be shown in a simple experiment. Firstly, get a cup of cornstarch (easily available in the supermarket) pour it in a shallow plate. Add half a cup of water slowly to the flour and mix it until you get something like the picture on the left. If is too watery you can add more cornstarch or just left it there to dry (but take a longer time). Remember this will dry up to form a solid so never pour this in the drain and clog it. Throw it in a rubbish bin. However you can also keep using it by adding water to it so you do not need mix it again to show this experiment.

You can try to punch your mixture, you will feel that it feel like solid as you are forcing the starch molecules to become close together as water is trapped between the starch chain. When you just touch gently, the cornstarch will flows again.

All fluids have a property known as viscosity - the measurable thickness or resistance to flow in a fluid. Newton said that viscosity is a function of temperature. You can observe that heated honey has viscosity less than the cold honey. The cornstarch and water mixture and quicksand are both examples of non-Newtonian fluids because their viscosity changes when stress or a force is applied and not due to the temperature.

Quicksand is created when water floods or saturates an area of loose sand and the sand is begins to move around. Think of quicksand as a soupy mixture of sand and water that is constantly being stirred. When the water in the sandy soil cannot escape, it creates a liquid-like soil that can no longer support any weight. If an excessive amount of water flows through the sand, it forces the sand particles apart. This separation of particles causes the ground to loosen, and any weight on the sand will begin to sink through it.

So this experiment is to shows the behavior of quicksand, as the cornstarch is like the sand which is flooded with water. This also tell us that when we encounter quicksand do not force yourself to get out of it as the greater the force you applied the harder the sand will be and your leg will get stuck even more. So one way is to relax wait for it to soften then move it out. Another way is to lie on your back to keep yourself afloat and slowly paddle. Actually I saw this in the website however I don't really encourage it as who know you may get panick and increase your force end up you may sink even more.