When a Fortins barometer is used to measure the pressure on the surface of the earth and in the top - Science - Force and Pressure

Question

When a Fortins barometer is used to measure the
pressure on the surface of the earth and in the top of the building
the main scale reading is found to be the same and the vernier
scale reading found to be 9 and 0 respectively If one M S D is 1 mm
and the number of vernier scale divisions is 10, calculate the
height of the building Taking the average density of air as 1 3
kg/cm3,and that of mercury is 13 6
g/cm3

Apurba Paul · Accepted Answer

One division of vernier means 0 1 mm
Suppose the height of the building is h Then the pressure decrease
due to climb up is ρairgh=0 0013×980×h
You have written air density as 1 3 kg/cm3 which can not
be possible so I am taking it as 1 3 kg/m3=0 0013
g/m3
Now the barometer reading change is 9-0×0 1=0 9 mm=0
09 cm
So the pressure change is
ρhggh=13 6×980×0 01 cm
So we have
13 6×g×0 09=0 0013×g×hh=13 60
0013=10462 cm≈10 4 m