Question

The pilot of an airplane reads the altitude 6400 m and the absolute pressure 46 kPa when flying over a city. Calculate the local atmospheric pressure in that city in kPa and in mmHg. Take the densities of air and mercury to be 0.828 kg/m3 and 13,600 kg/m3, respectively.

The local atmospheric pressure in the city in kPa is ?

The local atmospheric pressure in the city in mmHg is ?

Answer 1

1. 6.672 kPa

2. 49.05 mm of mercury

Step-by-step explanation:

h = 6400 m

Absolute pressure, p = 46 kPa = 46000 Pa

density of air, d = 0.823 kg/m^3

density of mercury, D = 13600 kg/m^3

(a) Absolute pressure = Atmospheric pressure + pressure due to height

46000 = Atmospheric pressure + h x d x g

Atmospheric pressure = 46000 - 6400 x 0.823 x 10 = 6672 Pa = 6.672 kPa

(b) To convert the pressure into mercury pressure

Atmospheric pressure = H x D x g

Where, H is the height of mercury, D be the density of mercury, g be the acceleration due to gravity

6672 = H x 13600 x 10

H = 0.04905 m

H = 49.05 mm of mercury