Question

what is absolite and guage pressure of the gas above the liquid surface in tha tank (diagram).​

Answer 1

Explanation:

Take the density of oil as 800 kg/m3 , density of mercury as 13.6 × 103 kg/m3 , atmospheric pressure as 1.0 × 105 N/m2 and g = 10 m/s2 .

As the points A and Bare at the same horizontal level in mercury, the pressure at these points is the same. Now, if P is the absolute pressure of the gas and P0 is the atmospheric pressure, then pressure at A is PA = P + (1.5 + 2.0) × 800 × 10 PA = P + 0.28 × 105 N/m2 Similarly pressure at B is PB = P0 + (1.0 + 2.0) × 13.6 × 103 × 10 PB = P0 + 4.08 × 105 N/m2 Using PA = PB´ Gauge pressure we get P – P0 = 3.8 × 105 N/m2 and Absolute Pressure P = (1.0 × 105 + 3.8 × 105 ) Pa P = 4.8 × 105 Pa.Read more on Sarthaks.com - https://www.sarthaks.com/454746/find-the-absolute-and-gauge-pressures-the-gas-above-the-surface-oil-the-tank-shown-the-figure

Answer 2

The proper question is

Find the absolute and gauge pressures of the gas above the surface of the oil in the tank shown in the figure.

Take

density of oil as 800 kg/m3 ,

density of mercury as 13.6 × 103 kg/m3 , 

atmospheric pressure as 1.0 × 105  N/m2 and

g = 10 m/s2 .

Explanation:

As the points A and B are at the same horizontal level in mercury, the pressure at these points is the same.

Now, if P is the absolute pressure of the gas and P0 is the atmospheric pressure, then pressure at A is

PA = P + (1.5 + 2.0) × 800 × 10

PA = P + 0.28 × 105 N/m2

Similarly pressure at B is

PB = P0 + (1.0 + 2.0) × 13.6 × 103 × 10

PB = P0 + 4.08 × 105 N/m2 

Using PA = PB´ 

Gauge pressure

P – P0 = 3.8 × 105 N/m2

Absolute Pressure

P = (1.0 × 105 + 3.8 × 105 ) Pa

P = 4.8 × 105 Pa.

❤