An air pressure intensity at A is 1/10 N/mm2 (absolute) having h1 = 0.25, h2 = 0.15. What is the pressure at B (absolute)?

An air pressure intensity at A is 1/10 N/mm2 (absolute) having h1 = 0.25, h2 = 0.15. What is the pressure at B (absolute)? Correct Answer P_B= 108 × 10^-3N/mm²

Concept-

• The pressure at any point in a fluid at rest is obtained by the hydrostatic law which states that the rate of increase of pressure in a vertically downward direction must be equal to the specific weight of the fluid at that point.
• P= ρgh Where ρ = Density of the fluid, h = Depth of the point from the free surface, g = acceleration due to gravity 
• In the above equation P = Gauge Pressure as it is measured with respect to the atmospheric pressure.

• The magnitude of atmospheric pressure is 101.325 Pa.

Calculation:

Air pressure intensity at A = 1/10 N/mm²(absolute) = 0.1 x 10⁶ Pa = 10⁵ Pa

The language of the question is not clear, but it is asked to find the pressure at Point B, so from the given options, the unit of option 2 is only matching with the unit of pressure, so option 2 will be the most appropriate answer from the given options.

If exact calculations will be done, the solution will be:

101.325 + ρgh = 10⁵

101.325 + ρ × 9.81 × 0.25 = 10⁵

ρ = 40733.40 kg/m³

Then, P at h = 0.15 

P_B = 101.325 + 40733.40 × 9.81 × 0.15

P_B = 60040.5231 Pa