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# States of Matter

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What Would Newton Say?

### What Would Newton Say?

Credit: United States Geological Survey
Source: http://commons.wikimedia.org/wiki/File:Mitch-_Casita_Mudslide.JPG

Liquefied mud flows down a mountainside in Nicaragua. Mud is usually a solid. But under some conditions, mud may turn to a liquid state and flow downhill.

#### The Back Story

• All fluids (liquids and gases) can flow, but they resist flowing to some degree. Some fluids resist flowing more than others (think honey vs. water). Resistance to flowing is called viscosity.
• Most fluids have more-or-less constant viscosity at a given temperature. Such fluids are called Newtonian fluids. That’s because they behave as first described by Isaac Newton in the 1600s.
• A few fluids are non-Newtonian fluids. These fluids behave very strangely. Their viscosity can change. Sometimes they act like liquids. Sometimes they act like solids.
• An example of a non-Newtonian fluid is oobleck, a cornstarch-and-water mixture you may have made in school or at home. It’s fun to play with oobleck because it runs through your fingers like a liquid but acts like a solid if you squeeze it. You can see some oobleck and learn how to make it by watching the video below:

#### Can You Apply It?

1. What is a non-Newtonian fluid?
2. Besides oobleck and mud, what are some examples of non-Newtonian fluids?
3. What are examples of forces that change the viscosity of non-Newtonian fluids?
4. What happens when the stress is removed from a non-Newtonian fluid?
5. Why might an earthquake cause a mudflow?
6. Why would a non-Newtonian fluid be good for body armor?

1. [1]^ Credit: United States Geological Survey; Source: http://commons.wikimedia.org/wiki/File:Mitch-_Casita_Mudslide.JPG; License: CC BY-NC 3.0

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