In everyday life the term viscosity has a certain meaning, but it can take on another according to its scientific explanation. Thus, when touching certain sticky and dense substances we can say that they are viscous. This is what happens with honey, some dairy products, mustard, some sauces or cosmetic products. Based on scientific criteria, viscosity is a law defined by Isaac Newton.
From a scientific point of view
Some fluid substances exhibit some degree of internal friction and this phenomenon is known as viscosity. This is a frictional force between adjacent layers of fluids. In other words, viscosity is a resistance in the form of internal friction. In liquids, viscosity is mainly due to the electrical cohesion forces of the molecules that form matter. In gases, this phenomenon occurs due to collisions between molecules. From a scientific point of view , the study of viscosity must be located in the area of fluid mechanics.
Newton’s Law of Viscosity
Viscosity is the friction between the different layers of a fluid. If a certain force is applied to each plate, this generates a strain on the fluid. Thus, the fluid is viscous when its mechanical energy is not constant, just as the fluid is not viscous when it remains constant. This idea was explained by Newton through a law that bears his name. This law states that in a fluid the frictional stress applied in one direction is proportional to its velocity and this situation is measurable with a coefficient of viscosity.
Fluid is a substance that deforms continuously, under the action of forces that can be a gas or a liquid. If we think of a tube with a certain fluid inside it, there are a number of aspects that determine the behavior of this fluid:
1) pressure change;
2) the height of the tube (the deeper the greater the pressure);
3) the area of the tube (the smaller the area, the lower the pressure);
4) the flow velocity.
The viscosity of oil in engines
All liquids have a degree of viscosity and compared to oils some have more viscosity than others. In order for a machine‘s engine to work properly, the oil must have good adhesion to the metal. One has to think that oil protects the moving parts of an engine and therefore its viscosity must adapt to the temperature changes that affect each engine.