A BRIEF OF “NEWTON’S LAW OF VISCOSITY”,

“Newton’s law of viscosity” is the most significant among the laws of velocity that is mostly focused on the proportion of shear stress and the rate of strain . Apart from that, as per the law of Newton, the viscosity of a fluid is mostly related to the velocity gradient along with shear stress. “F= ηA(dv/dz)” is the basic formula for the measurement of viscosity of a fluid and in this formula, F stands for the viscous force. Apart from that, η represents the coefficient value of viscosity and A represents the area of fluid on which the rate of viscosity varies mostly and dv/dz represents velocity gradient .            

Concept of Viscosity

“Newton’s law of viscosity” is mainly observed in the application of mechanical stress that guides recognize the relationship and the coefficient of shear stress and the rate of the strain of fluid. According to “Newton’s law of viscosity”, the rate of shear stress is constant and it depends on the temperature and the pressure of the fluid. . There are two different types of adjacent layers in the fluid, which are directly influenced by the negative value of the velocity gradient. According to “Newton’s law of viscosity”, there are two principal types of fluids: Newtonian fluids and non-Newtonian fluids.              

Concept of Viscosity unit

The Viscosity unit is mainly of two types one is SI unit and the other is the CGS unit. In the SI unit, the viscosity is measured with the formula of “Pascal seconds (Pa·s) or kg·m−1·s−1” and in the CGS unit, it is measured with Poise. The viscosity unit mainly depends on the areas of fluid that are closely connected with the two different adjacent layers. Apart from that, difference in the rate of velocity has also a great influence on the Viscosity unit. Besides this, the inner distance between two adjacent layers of fluid.         

The formula of Viscosity: Concept  

The formula of viscosity in perspective of “Newton’s law of viscosity” that is mostly used is N.s.m-2. The SI unit of the form of kinematic viscosity is measured through m2/s whereas in the mode of the CGS unit the form of viscosity is measured through cm2/s. The rate of viscosity differs due to the change of temperature and most importantly on the composition and the characteristics of Newtonian fluid as well as non-Newtonian fluid. Apart from that, the size and state of the molecules and the strength of fluid depend on some internal and external force is a great factor that influences the rate of viscosity of a fluid.         

Different types of Newtonian fluids   

• Two principal types of fluids are seen from the perspective of “Newton’s law of viscosity”, one is Newtonian fluid and the other is a non-Newtonian fluid. 
• Examples of a Newtonian fluid are water, different types of mineral oil, and alcohol whereas the non-Newtonian fluid includes toothpaste, ketchup, and paint composition of liquid that creates a greater thickness.   
• Dilatant is a significant type of Newtonian fluid and in this type of fluid, the viscosity rate differs due to increases in shear stress and temperature of the fluid.           

Conclusion 

As per “Newton’s law of viscosity”, the increase or decrease rate of viscosity with the change of pressure of the fluid and the composition of the fluid.  In normal temperature, if the pressure increases then the rate of velocity is also changed accordingly. The viscosity of a fluid is integrally related to the physical property of a fluid that is characterized by the resistance of both types of fluid Newtonian fluid as well as non-Newtonian fluid. According to “Newton’s law of viscosity”, the phenomenon of viscosity depends on the resistance of the liquid or gas that can change the shape of molecules. Apart from that, the rate of viscosity depends on the stress amount of the application that has been found in direct proportion and the velocity difference of the different layers of the fluid.