91影视

In a manometer, the change in pressure at a place is determined by the height of the reading in the curved open and straight end.

The atmospheric pressure is P_atm = 1040m bar.

The mercury at the open end is h = 18.5 cm higher in the first case.

The mercury at the open end is h' = 5.6cm lower in the first case.

The density of mercury is 蟻 = 13.6 x 10³ kg/m³.

Here, g =9.8 m/s² is the acceleration due to gravity.

The atmospheric pressure is calculated as,

\begin{aligned}{P_{atm}}=1040\;{\rm{mbar}}\times\frac{{{{10}^{-3}}\;{\rm{bar}}}}{{1\;{\rm{mbar}}}}\\{P_{atm}}=1040\times{10^{-3}}\;{\rm{bar}}\\{P_{atm}}=1040\times{10^{-3}}\;{\rm{bar}}\times\frac{{1\;{\rm{Pa}}}}{{{{10}^{-5}}\;{\rm{bar}}}}\\{P_{atm}}=1040\times{10^2}\;{\rm{Pa}}\end{aligned}

The absolute pressure at higher than the normal height is,

\begin{aligned}P'={P_{atm}}+h rho g\\=\left({1040\times{{10}^2}\;{\rm{Pa}}}\right)+\left({18.5\times{{10}^{-2}}\;{\rm{m}}}\right)\times\left({13.6\times{{10}^3}\;{\rm{kg/}}{{\rm{m}}^{\rm{3}}}}\right)\times\left({9.8\;{\rm{m/}}{{\rm{s}}^{\rm{2}}}}\right)\\\approx129\times{10^3}\;{\rm{Pa}}\end{aligned}

Hence, the absolute pressure is 129 x 10³ Pa.

The absolute pressure at lower than the normal height is,

P鈥欌�� = p_atm 鈥� h鈥櫹乬

On plugging the values in the above relation.

Hence, the absolute pressure is 9.6 x 10⁴ Pa.