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Zidbits – Learn something new everyday! | September 3, 2014

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How Do People Walk On Non-Newtonian Fluids?

How Do People Walk On Non-Newtonian Fluids?

You can do some pretty cool things with a non-Newtonian fluid. Even walk it if you’re quick enough. But what is it, how does it work and can you make your own? Let’s find out.

What Is A Non-Newtonian Fluid?

A non-Newtonian fluid is a liquid or fluid whose viscosity can change when stress or pressure is applied to it. Its name comes from the fact that non-Newtonian fluids do not behave according to the properties of liquid viscosity discovered by Sir Isaac Newton. These fluids will appear and act as a liquid, but when pressure is applied (even sound pressure as shown in the video at the bottom), it can behave like a solid.

How Does This Happen

In non-Newtonian fluids, the particles are packed very close to each other (they are touching), but they are still able to slip by each other. When you move the mixture slowly, the suspended particles have time to move and slip by each other – this is how a normal liquid acts. However, when you suddenly apply pressure to the mixture, the particles do not have enough time to move out of the way as they are quite large. This causes them to stay right where they are which causes the mixture to act and feel like a solid.

So I Can Walk On It?

If you fill a small swimming pool with enough, you could walk across it. This is because each footstep applies force to the fluid, firming it up under your foot. However, if you were to stop, you would sink. Any attempt to pull yourself up will firm up the fluid around your legs and feet. Quicksand works in a similar way.


How Do I Make My Own?

It’s easy to make some in your kitchen, the ingredients are likely already there! Place some cornstarch in a bowl, and slowly stir in a little water. Continue to stir and slowly add water until you begin to feel it thicken up. It’s generally 2 parts of cornstarch to 1 part water. To spice up the visual aspect, add some bright food coloring. You’ll know you have the right mixture when you can pick it up and roll it into a ball. The moment you stop however, it should lose cohesion and ‘melt’ out of your hands as it turns back into a liquid.

Bonus Fact: Non-Newtonian fluids could very well be an important part in the body armor of the future. Since they are usually flexible, they would allow soldiers more freedom of movement when not under attack. When the time comes when they must protect against a speeding bullet, their unique qualities would allow them to instantly harder, performing like traditional armor, perhaps even better.

Bonus Video


Comments

  1. Tyler D

    A buddy of mine made his own small pool of it for the kids in his class (he’s a teacher). He was even put on the front page of our local newspaper. It was amazing fun. You could run across it without sinking but if you stood still, it was like quicksand and you would sink. The kids had an absolute blast playing around on it. I recommend doing it if you’re looking for something interactive to present your class. It’s a great teaching tool.

    What nobody ever talks about, however, is the cleanup. The stuff is a nightmare to cleanup when you make a huge batch. It’s heavy and doesn’t get thrown away easily. It’s also not cheap to make a pool filled with the stuff. I imagine mythbusters could afford something like that, but it put quite a dent in my friend’s pocket since he paid for it himself. The school did reimburse him some of the money, but not the whole thing.

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