Calculate the pressure exerted by 0.8 m vertical length of alcohol of density 0.8 g cm$^{-3}$. (Acceleration due to gravity (g)= 10ms^-2).
(A) 3200 Pa
(B) 6400 Pa
(C) 800 Pa
(D) 5000 Pa

Hint:The given problem is from pressure measurement of fluids. As we know that the pressure in fluids depends on density of fluid and length of fluid in the tube. So here we use this concept to solve this given problem.

Complete step by step answer:
The pressure measurement in liquids depends on the density of fluid and the length of liquid in the tube. The pressure exerted by the liquid at the bottom of tube is given by
$P = \rho gh$
Where, P is the pressure at bottom due to liquid
ρ= density of liquid
g= gravitational acceleration
h= length of liquid in tube
The values of these parameters given in question as
$\rho = 0.8gc{m^{ - 3}}$
$\rho = 0.8 \times 1000g{m^{ - 3}}$
$\rho = 800g{m^{ - 3}}$
g= 10m/s²
h= 0.8 meter
We apply these values in formula of pressure as
$P = 800 \times 10 \times 0.8$
$P = 6400pascal$
The pressure exerted by liquid is 6400 pascal. So the correct option is option (B).
Pressure is defined as the perpendicular force exerted on unit area. The SI unit of pressure is N/m², which is equal to Pascal. The liquids exerts pressure on the bottom of the tube due to their weight. The amount of pressure in liquids is given by the hydrostatic law of pressure. It states that the pressure exerted by length of liquid is proportional to the density and length of liquid.
The pressure increases if we move downward from the liquid surface and it decreases if we move towards the liquid surface.

Note:We should always remember that, the pressure always considers the perpendicular component of force exerted on the surface. This is also true for liquids. If we move downwards then due to increased weight of liquid the exerted pressure will also increase.