# What Is a Non-Newtonian Fluid?

A non-Newtonian fluid is a fluid whose viscosity is variable based on applied stress. The most commonly known fluid of this kind is cornstarch dissolved in water. Contrast with Newtonian fluids like water, whose behavior can be described exclusively by temperature and pressure, not the forces acting on it from second to second. These fluids are fascinating substances that can be used to help us understand physics in more detail, in an exciting, hands-on way.

If you punch a bucket full of a shear thickening non-Newtonian fluid, the stress introduced by the incoming force causes the atoms in the fluid to rearrange so that it behaves like a solid. Your hand will not go through. If you shove your hand into the fluid slowly, however, it will penetrate successfully. If you pull your hand out abruptly, it will again behave like a solid, and you can literally pull a bucket of the fluid out of its container in this way.

A shear thinning non-Newtonian fluid behaves in the opposite way. In this type, the fluid becomes thinner, rather than thicker, when stress is applied. Also called pseudoplastic, examples of this type of fluid include ketchup, toothpaste, and paint. The effect doesn't usually last for long in either type, continuing only as long as the stress is applied.

Non-Newtonian fluids help us understand the wide variety of fluids that exist in the physical world. Plastic solids, power-law fluids, viscoelastic fluids, and time-dependent viscosity fluids are others that exhibit complex and counterintuitive relationships between shear stress and viscosity/elasticity. However, non-Newtonian fluid is probably the most exciting to play with.

A search for non-Newtonian fluid on YouTube brings up some interesting results. On several game shows, hosts or contestants run across big vats of shear thickening non-Newtonian fluid, able to traverse them unless they stop - in which case they sink immediately. When combined with a oscillating plate, these fluids demonstrate other unusual properties, like protruding "fingers" and holes that persist after creating them. An oscillating plate applies stress on a periodic basis, rapidly changing the viscosity of the fluid and putting it in an odd middle ground between a liquid and a solid.

A practical application for shear thickening non-Newtonian fluids may be in body armor of the future. Since such fluids are usually flexible, they would allow soldiers to move freely when not under attack. But if confronted with a speeding bullet, they would quickly harder, performing like traditional armor. More research is necessary to see if non-Newtonian fluids are suitable for the military, but until then, it's sure fun to play with.

## Discussion Comments

Can somebody please inform me of a point which I am struggling with? I get the Newtonian and Non-Newtonian fluids but the question which I am trying to answer on my assignment also refers to ideal solids and ideal fluids. Does anybody know what these are or where I can find information about them please?

Am I the only one completely lost? I didn't get half of this. I have to do a report on this and I'm as lost as all get out.

why do non newtonian fluids change their viscosity under stress?

@comment no26: Non-newtonian liquid running through our body is blood.

humans have a Non-newtonian fluid that runs throughout our bodies. what is it? Help!0

I would like to answer tons of peoples' questions.

RE: mercury a non-newtonian fluid? Mercury is a newtonian fluid. It is not a polymer, but ratherm an element, and for something to be a non-newtonian fluid it must be a polymer.

RE: Able to stop a bullet? As far as Mythbusters has done, the answer is no. Hopefully you haven't attempted to use it in that way.

RE: Any newtonian fluids in this world? There are absolutely tons of newtonian fluids. Most fluids are Newtonian.

RE: Why it is called non-newtonian fluid? The fluids do not follow the laws that Newton discovered about the behavior of fluids, hence "non-newtonian." -The Answer-er

so, are there any newtonian fluids in this world? if there are, can you tell me what they are? thanks. taufiq, university of indonesia

I am a Diploma engineer. is mercury a non-newtonian fluid? if not, explain to me. Thanks, Vinoth KG

why it is called non-newtonian fluid?

what's the density of cornstarch and water?

Just so you know, non-Newtonian fluids will not stop a bullet. The bullet is moving so fast that the soldier would need a suit of armor about five feet thick to stop a bullet.

The bullet does not have much surface area when encountered straight on. If it is a rapidly fragmenting bullet, it may be slowed down. Armor piercing bullets do not fragment and therefore are much harder to stop.

are non newtonian fluids able to stop a bullet?

I'm an engineering student looking for a shear thickening non newtonian fluid (like corn starch) but one that will not dry out like corn starch does. Does anybody know of any that I can research?

I think this may have just saved me from epically failing in my lab report (we did a lab where we mixed cornstarch and water). thank you so much!

Are the d30 molecules that are being used for military purposes are also composed of non newtonian fluids?

Thank you so much for this information,it help me for my final project, and it's easy for any student to understand what is written. I hope to find more articles like that. thank you again.

i'm using non-newtonian floods for a science project like toothpaste and ketchup and cornstarch and water on a speaker.

you can make a newtonian fluid by mixing 2 cups of cornstarch and 1 cup of water together. Mix well and enjoy!

What are some kinds of non-newtonian fluids?

-Josh

what properties does it have?

Newtonian fluids are not that common. Non-Newtonian fluids are more common in practical applications. Newtonian fluids are difficult to find because of their highly specific conditions. Not all fluids are Newtonian, more often than not, fluids are non-Newtonian. Realistically, the fluids that a person encounters on a daily basis are nonhomogenous, therefore their viscosity may differ widely---including water! Tap water is not 100% H20, rather it is H2O plus any filtrates and minerals that may not have been removed in the municipal filtering process. As a result the viscosity may differ and as a result, its behavior may differ. Though this may not produce a considerable difference, it is enough to cause a variation in experimental results.

Ketchup is a non-Newtonian fluid because it is an amalgamation of different components--water, corn syrup, tomato paste, etc. (the constituents may vary from manufacturer to manufacturer) As the force/pressure on ketchup in a bottle is increased, the dynamic viscosity of the fluid decreases. This is why ketchup is easier to squeeze out of the bottle if you apply more force.

I love playing with non-newtonian fluids! I wrote about them for science, so I'm hoping for extra credit.

Yes, natural gas is a Newtonian fluid.

hey what other materials can be added together to make a non-newtonian fluid?

Yes. Most fluids are Newtonian. Non-Newtonian fluids are rare special cases, like corn starch in water.

is natural gas a newtonian fluid?

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