* Newton's Law of Viscosity: This law states that the shear stress (force required to deform the fluid) is directly proportional to the shear rate (how fast the fluid is deformed). This is true for many common fluids like water and air.
* Non-Newtonian Fluids: These fluids don't follow this simple linear relationship. Their viscosity can change depending on factors like:
* Shear rate: The faster you try to move the fluid, the thicker it can become (like ketchup) or the thinner it can become (like paint).
* Temperature: Their viscosity can change significantly with temperature.
* Time: Some non-Newtonian fluids can change their viscosity over time.
The name "non-Newtonian" highlights that their behavior deviates from the predictable, linear behavior described by Newton's law.
To better understand, think of it like this:
* Newtonian fluid: Imagine a regular liquid, like water. If you stir it, it resists with a consistent force. The harder you stir, the harder it resists, but the relationship is always linear.
* Non-Newtonian fluid: Think of something like cornstarch mixed with water. If you stir it gently, it's like a liquid. But if you hit it hard, it becomes solid and resists the force. This is because the viscosity of the mixture changes drastically with the applied force.
So, the name "non-Newtonian" is a simple way to categorize fluids that don't conform to the simple model of Newtonian behavior. They exhibit more complex and interesting properties that make them fascinating to study and useful for various applications.
