Exploring the Differences Between Viscosity and Upthrust in Liquids

In summary, viscosity and upthrust are two different effects that occur in liquids. Viscosity is a result of thermal energy and leads to irreversibility, while upthrust is caused by the liquid's lack of shape and involves mechanics. While both effects do have an electrostatic component, it is not necessary to understand electricity to explain them. Viscosity is an internal phenomenon, while upthrust is dependent on an external field, such as gravity.
  • #1
Cheman
235
1
Viscosity and Upthrust...

Viscosity and upthrust are both forces which occur in liquids, and must both rely on electrostatic effects. So what is there difference between them? What causes these 2 distinctly different effects?

Thanks in advance. :smile:
 
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  • #2
none of the really rely on the electrostatic effects. That means that we do not need to know anything about electricity to explain them. What is important is that the liquid molecules may collide to each other.

The upthrust comes from the fact that liquid has no shape. So at the equilibrium the pressure on the piece of liquid is the same in all directions. That is pure mechanics, the potential, elastic and kinetic energy are players there.

The viscosity comes from thermodynamic. The important player in this game is thermal energy. Now the process becomes irreversible. That is kind of tricky and non-trivial- you need to use reversible mechanical equation to introduce irreversibility. Without going into deep, you may just use known thermodynamical equations. Friction heats.

Both viscousity and upthrust exist in gases, too.
 
  • #3
But surely it must be an electrostatic effect if it relies on collisions? Afterall, particles when they collide do not actually touch as we often depict them classically ( unless traveling ridiculously fast, eg - after passing through a particle accelerator.) but simply experience repulsion effects.
 
  • #4
yes, of course it is electrostatic because we know that there is no other force responsible. But we don't need to know that to explain these effects. Archimedes knew nothing about the Coulomb. The problems are limited the mechanics and thermodynamics, no theory of electricity is needed (in a first approximation).

But if we are working with high energies, when atom and molecules can break down, then yes, we need to know the nature of the binding forces. At low energies only the intermolecular forces are important, and, in the first approximations, we can explain almost everything if we simply assume elastic collisions of solid structures.

I probably got your question.
The viscosity is an energy redistribution between constituents. It exists without any external force or field. The upthrust exist only if we have an external field- there is no upthrust without gravitation.

Viscosity appears because of the internal degrees of freedom of the macroscopic body. Upthrust is due to the interaction of the macroscopic body with the external field.
 
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1. What is viscosity?

Viscosity is a measure of a liquid's resistance to flow. It is determined by the internal friction within the liquid, and is influenced by factors such as temperature and molecular structure.

2. How does viscosity differ from upthrust?

Viscosity and upthrust are two different properties of liquids. Viscosity is related to a liquid's resistance to flow, while upthrust is the upward force exerted on an object immersed in a liquid.

3. What factors affect the viscosity of a liquid?

The viscosity of a liquid can be affected by a variety of factors, including temperature, molecular structure, and the presence of additives or impurities. In general, higher temperatures and simpler molecular structures lead to lower viscosity, while additives or impurities can increase or decrease viscosity depending on their properties.

4. How does upthrust affect the movement of objects in liquids?

Upthrust, also known as buoyancy, is responsible for the floating of objects in liquids. The upward force exerted by the liquid on an object is equal to the weight of the liquid displaced by the object. This allows objects with lower density than the liquid to float, while objects with higher density will sink.

5. How are viscosity and upthrust related?

Viscosity and upthrust are not directly related, as they are two distinct properties of liquids. However, both can affect the movement of objects in liquids. High viscosity can make it more difficult for objects to move through a liquid, while upthrust can determine whether an object will float or sink in a liquid.

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