Viscosity
Viscosity is a physical property of fluids. It shows resistance to flow.[1] In a simple example, water has a low viscosity, as it is "thin". Syrup and tar, on the other hand, have a high viscosity, as they are "thick". A way to test for viscosity is the speed at which the substance runs down a slope. Syrup would reach the bottom very slowly, and water would be much quicker.
There are two types of viscosity: dynamic viscosity, measured in pascal seconds, and kinematic viscosity, measured in metres squared per second .[2]
Viscosity is used as a way to predict when volcanoes erupt. When the lava comes out very thickly (viscous), there is more chance that it will erupt violently. This is because the lava has a hard time getting out and may burst out when it can. If the lava is thin (low viscosity), then it just flows out like water.[3]
The word viscous comes from the Latin root viscum, meaning sticky.[4]
Viscosity Media
Illustration of a planar Couette flow. Since the shearing flow is opposed by friction between adjacent layers of fluid (which are in relative motion), a force is required to sustain the motion of the upper plate. The relative strength of this force is a measure of the fluid's viscosity.
Common logarithm of viscosity against temperature for B2O3, showing two regimes
In the University of Queensland pitch drop experiment, pitch has been dripping slowly through a funnel since 1927, at a rate of one drop roughly every decade. In this way the viscosity of pitch has been determined to be approximately 230 billion (2.3×1011) times that of water.[6]
References
- ↑ Elert, Glenn (2021). "Viscosity". The Physics Hypertextbook.
- ↑ "Quantities and Units of Viscosity". Uniteasy.
- ↑ "What is Viscosity? (with pictures)". wiseGEEK.
- ↑ "viscous - Origin and meaning of viscous". Online Etymology Dictionary.
- ↑ Fluegel 2007.
- ↑ Edgeworth, Dalton & Parnell 1984, pp. 198–200.