ANS:A - 1 cm²/second

Kinematic viscosity is a measure of a fluid's internal resistance to flow under gravitational forces. It is defined as the ratio of dynamic viscosity to fluid density. The unit of kinematic viscosity in the CGS (centimeter-gram-second) system is the stoke (St). One stoke is defined as the kinematic viscosity of a fluid in which a force of one dyne per square centimeter maintains a velocity gradient of one centimeter per second per centimeter. In simpler terms, it is the viscosity of a fluid that flows through an area of one square centimeter at a rate of one centimeter per second under the influence of gravity. Mathematically, kinematic viscosity (ν) is given by: ν=μρ\nu = \frac{\mu}{\rho}ν=ρμ​ where:

• ν\nuν is the kinematic viscosity,
• μ\muμ is the dynamic viscosity,
• ρ\rhoρ is the density.

The unit of dynamic viscosity (μ\muμ) in the CGS system is poise (P), and the unit of density (ρ\rhoρ) is grams per cubic centimeter (g/cm³). Since: ν=poise (P)density (g/cm3)\nu = \frac{\text{poise (P)}}{\text{density (g/cm}^3\text{)}}ν=density (g/cm3)poise (P)​ 1 poise (P) = 1 g/(cm·s) If the density is 1 g/cm³, the kinematic viscosity is: ν=1 g/(cm\cdotps)1 g/cm3=1 cm2/s\nu = \frac{1 \text{ g/(cm·s)}}{1 \text{ g/cm}^3} = 1 \text{ cm}^2/\text{s}ν=1 g/cm31 g/(cm\cdotps)​=1 cm2/s Thus, one stoke (St) is defined as: 1 St=1 cm2/s1 \text{ St} = 1 \text{ cm}^2/\text{s}1 St=1 cm2/s In summary, one stoke (St) is a unit of kinematic viscosity equivalent to one square centimeter per second (1 cm²/s). This unit is used to express how easily a fluid flows under its own weight, taking into account both its internal friction and density.