The heights of mercury in a manometer are 2cm and 8cm. Find the pressure of the gas in the cylinder? Patm=105Nm−2
The density of mercury, ρm = 13600kgm−3.
Acceleration due to gravity, g=10ms−2
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Solution
Let the pressure of gas contained in the chamber be Pg.
Consider the lowest point of U-tube.
Pressure from the right column of U-tube is: P1=Patm+ρmgh1
Pressure from the left column of U-tube is: P2=Pg+ρmgh2
According to Pascal's Law, P1=P2 Patm+ρmgh1=Pg+ρmgh2 Pg=Patm+ρmg(h1−h2) Pg=105+[13600×10×(8100−2100)] Pg≈1.08×105Pa