The water manometer above is measuring the pressure of gas supply. if the specific gravity of mercury is 13.6 and the atmospheric pressure is 70cm of mercury what is the total pressure of the gas supply in cm of water
67cm
73cm
949cm
952cm
955cm
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Discussions (13)
Relative density of mercury = density of mercury/density of water
R.d of Hg = p of Hg/p of water
But R.d of Hg = 13.6
p of Hg = not given
p of water = 1000kg/m³
: . p of Hg = 13.6 × 10000 = 13600kg/m³
we are asked to find the pressure of the gas supply in cm of water and not of meecury
Then equating the pressure formular for water to that of mercury, we have:
phg mercury = phg water
p = 13600kg/m³ p = 1000kg/m³
h = 70cm h = xcm
we need to get the height of the water
: . 13600 × 70 × g = 1000 × x × g
x = (13600 × 70)/1000 = 952000/1000
: . x = 952cm
height of water = 952cm
: . The pressure in cm of water is, P = H + h
here h = 3cm and H = 952cm
: . P = 952 + 3 = 955cm
Correct ans is E
Myschool pls correct, the question requires the pressure of the gas supply in cm of water
Atmospheric pressure = 70cmHg (which is the height of mecury)
pressure = pgh = pwghw
Where
Pw = density of water
hw = height of water
ph = pwhw
13.6*70 = 1*hw
hw = 952cm
Pressure of gas in cm of water = 952 + 3 = 955cm
