Viscosity is not dependent on the state of the fluid which is why when the fluid is at rest or in motion, 1 Poise will remain constant. Ques: What will be the state of the viscosity of the fluid if it is at rest? (2 marks)Īns: The viscosity of fluid when at rest will be 1 Poise. (2 marks)Īns: According to Newton’s law of viscosity shear stress between the adjacent layers of the fluid is proportional to the velocity gradients between the two layers.
The area of contact between the two adjacent layers.Ques: What are the factors on which viscosity depends? (3 marks)Īns: The factors on which viscosity depends are as follows: Sample Questions based on Unit of Viscosity The unit of viscosity in SI units is Kg/ms and in CGS it is dyne s cm^(-2).The coefficient of viscosity is considered as the measure of viscosity.Viscosity is the fluid resistance against its flow and it comes into action due to the relative motion of the internal layers of the fluid.The viscosity of liquids decreases with the increase in temperature, whereas in gases viscosity increases with an increase in temperature.For example, Blood is more viscous compared to water. In general, thick liquids are more viscous than thin liquids.Recommended video: Points to Remember based on Unit of Viscosity Furthermore, other abbreviations are sometimes used such as SUV (Saybolt universal viscosity) or SSU (Saybolt seconds universal). Earlier, the kinematic viscosity was measured by using Saybolt viscometer where the units were expressed in Saybolt universal seconds (SUS). Some non-standard units of viscosity are the Reyn which is a British unit of dynamic viscosity. Sometimes the unit centistokes (CST) is also used.The cgs unit for kinematic viscosity is stoke (St) which was named after Irish mathematician and physicist Sir George Gabriel Stokes.It is also widely used in ASTM standards, as centipoise (cP).In the CGS standard, the unit of viscosity is poise (P) which is used in honor of a French physiologist Jean Léonard Marie Poiseuille.The unit is generally called Decapoise or Poiseulle. In SI standards, the unit of η is Kg/ms, and N s m^(-2). Now we can substitute the individual units and find the units in SI and CGS. Η = F/A*dx/dv, neglecting the –ve sign for the sake of convenience.įrom the equation, we can determine the dimension of η as M/LT. Since the coefficient of viscosity is regarded as the measure of viscosity, the unit of coefficient of viscosity is considered as the unit of viscosity.
#Viscosity units pdf#
The above equation is known as Newton's formula for viscous force.ĭownload the PDF on Viscosity Unit of Viscosity Where η is the coefficient of viscosity, the negative sign implies that the viscous force is acting in the opposite direction of the fluid flow. The velocity gradient between the layers in contact, Consider the dragging force F tangentially between the layers of the fluid, and it is proportional to