Comparison of densities of liquids using Hare’s apparatus

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Comparison of densities of liquids using Hare’s apparatus

Liquids of different densities are placed in glass pots as shown above.
When the gas tap is opened each liquid rises to different height h1 and h2.Since they are subjected to the same gas supply,
-Measure the height of the liquids in the two arms, h1 and h2.




Example 1
Water and kerosene are placed in U-tube containing mercury as shown above. Determine the density of kerosene?

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Pressure of kerosene= Pressure of water (since both tube are open to the atmosphere)



h1ρ1=h1ρ1 8(1000)=10ρ1

ρ1=800 kgm−3

Example 2
The diagram below shows heights to which liquids A and B have risen in an inverted U-tube, when some air has been pumped at P. Find the density of liquid B if that of A is 800 kgm−3.[Ans: 𝜌=640 kgm−3]

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Example 3
The atmospheric pressure at the bottom of a mountain is 100000Pa. If the mountain is 800m high, and the density of air is1.25 kgm−3. Find the pressure at the top of the mountain.




Ptop=90000 Pa