Question

Poise is the unit of:
A) Surface tension
B) Capillarity
C) Viscosity
D) Buoyancy

Answer 1

Viscosity is the property of fluids. Viscosity is a measure of fluid’s resistance to flow. It speaks about the internal friction of a moving fluid.

Complete step by step answer:
Poise is the unit to measure viscosity.
(i) Poise, the unit to measure the viscosity can be denoted in the cgs system of units. $1Pa.s = 10poise$
(ii)The name of the symbol poise is derived from the scientist Poiseuille. Its symbol is $P$ and $1P = 1gc{m^{ - 1}}{s^{ - 1}}$
(iii) In the SI system of units, viscosity is measured with the unit called pascal second. Pascal second is represented as $Pa.s$.

$\therefore$ Hence the correct option is option (C).

Additional information:
(i) Viscosity is the property of fluids. Viscosity is a measure of fluid’s resistance to flow. It speaks about the internal friction of a moving fluid.
(ii) Viscosity is derived from the Latin word “Viscum” which means glue. So that we can understand that viscosity speaks about the thickness of the fluid. The liquid having high viscosity resists the flow more.
(iii) Newton’s law of viscosity states that the shear stress between the adjacent fluid layers is proportional to the velocity gradients between the two layers.
$\Rightarrow \tau \propto \dfrac{{du}}{{dy}}$ Where, $\tau$ represents the shear stress and $\dfrac{{du}}{{dy}}$ represents the velocity gradients between two fluid layers.
(iv) The ratio of shear stress and the shear rate is constant, for given temperature and pressure is called as the coefficient of viscosity. $\tau = \mu \dfrac{{du}}{{dy}}$ where $\mu$ represents the coefficient of viscosity.

Note:
The liquid whose viscosity changes with the change in the rate of deformation $\left( {\dfrac{V}{Y}} \right)$ is called Newtonian fluid. The liquid whose viscosity does not change with the rate of deformation is called Non-Newtonian fluids. Liquid water has a viscosity of $0.00890{\text{ }}P$ at $25^\circ C$ at 1 atmospheric pressure.