A closed tank contains 0.5 m thick layer of mercury (specific gravity ...
Given information:
- Thickness of mercury layer = 0.5 m
- Specific gravity of mercury = 13.6
- Thickness of water layer = 2.0 m
- Thickness of oil layer = 3.0 m
- Specific gravity of oil = 0.6
- Gauge pressure at the bottom of the tank = 196.2 kN/m2
- Density of water = 1000 kg/m3
- Acceleration due to gravity = 9.81 m/s2
To find: Pressure in the air space above the oil layer
We can solve this problem by considering the equilibrium of forces at different levels in the tank.
1. Pressure at the bottom of the tank:
The gauge pressure at the bottom of the tank is given as 196.2 kN/m2. Since this pressure acts on the mercury layer, we need to convert it into absolute pressure by adding atmospheric pressure. Assuming atmospheric pressure is 101.3 kN/m2, the absolute pressure at the bottom of the tank is:
Absolute pressure = Gauge pressure + Atmospheric pressure
= 196.2 kN/m2 + 101.3 kN/m2
= 297.5 kN/m2
2. Pressure at the interface of mercury and water:
The pressure at the interface of two immiscible fluids is equal. Therefore, the pressure at the interface of mercury and water is also 297.5 kN/m2.
3. Pressure at the interface of water and oil:
Again, the pressure at the interface of two immiscible fluids is equal. Therefore, the pressure at the interface of water and oil is 297.5 kN/m2.
4. Pressure at the top of the oil layer:
The pressure at the top of the oil layer can be determined by considering the weight of the water and oil layers above it. The pressure exerted by the water layer is given by:
Pressure due to water layer = Density of water × Acceleration due to gravity × Thickness of water layer
= 1000 kg/m3 × 9.81 m/s2 × 2.0 m
= 19620 N/m2
Similarly, the pressure due to the oil layer is given by:
Pressure due to oil layer = Density of oil × Acceleration due to gravity × Thickness of oil layer
= 0.6 × 1000 kg/m3 × 9.81 m/s2 × 3.0 m
= 17658 N/m2
Therefore, the total pressure at the top of the oil layer is the sum of the pressures due to water and oil layers:
Total pressure at the top of oil layer = Pressure due to water layer + Pressure due to oil layer
= 19620 N/m2 + 17658 N/m2
= 37278 N/m2
5. Pressure in the air space:
The pressure in the air space above the oil layer is equal to the total pressure at the top of the oil layer. Therefore, the pressure in the air space is 37278 N/m2, which is equivalent to 92.214 kN/m2.
Hence, the correct answer is option 'A' (92.214 kN/m2).
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