The discussion revolves around calculating the fractional decrease in pressure when a barometer is raised 35 meters. The context involves concepts from fluid mechanics and atmospheric pressure, specifically focusing on how height affects pressure in a column of air.
Multiple approaches have been presented, with participants sharing different calculations and results. Some have acknowledged discrepancies in their methods, while others have provided feedback and suggestions for re-evaluating assumptions. The discussion remains open, with no clear consensus reached.
Participants are working under the assumption of constant air density and are referencing specific values for air pressure and density at given conditions. There is also mention of forum rules requiring initial attempts before receiving assistance.
ZoeGab said:I have tried to work this problem in different ways and I have gotten different answers. This was my last attempt but it still does not seem right.
35 m of air at approx 29 gm/mole at 24.1 liter per mole at room temperature weighs 4.2 gram per cm squared.
The air pressure at sea level is 1035 grams per cm squared.
Raising the barometer 35 meters lowers the pressure 4.2/1035 or 0.4%.
zoegab said:here is another way with a different answer
change in pressure , Δp = ρgh
where,
ρ = density of medium = 1.184 kg/m3 (for air at 250 c)
g = acc due to gravity = 9.8 m/s2
h = height change = 35 m
=> Δp = 1.184*9.8*35 = 406.112 pa
1 atm = 101325 pa
=> 1 pa = 1/101325 atm
=> 406.112 pa = 406.112/101325 = 0.004 atm (approx)
ZoeGab said:take a look at this; where did I go wrong this time
ρgh = 1.15kg/m3*9.8*35 = 389.4*10-5 Pa