Weight of air?

[JAMIE MCG]

Myth Busters had an episode where they informed if you put a cylinder around the Eiffel Tower the air inside the cylinder would weight more than the iron,( material ), that floored me.

 

[Divin'Papaw]

Myth Busters had an episode where they informed if you put a cylinder around the Eiffel Tower the air inside the cylinder would weight more than the iron,( material ), that floored me.

Not quite sure I understand. So if the space under the Eiffel Tower were somehow made into a compressed air cylinder, the weight of the air would weight more than the steel in the cylinder, or the steel in the Eiffel Tower? Please explain more. I'm just curious.

 

[SparticleBrane]

I disagree with MythBusters.

Specifically...
The Eiffel Tower (including the spire) is 1,052ft tall and at it's widest point, 423ft wide.
Assuming a perfect cylinder (pi*[radius^2]*height), that's (pi)((423/2)^2) = 140,530.5 sq. ft. as the base, times 1,052ft for the height = 147,838,094.4cf inside the cylinder
At 0.08lbs/cf that's 11,827,047.55lbs of air. The metal in the tower weighs 7300 tons; if you include everything it's 10,100 tons. That's 14,600,000lb or 20,200,000lbs depending on if you want to include just the metal or the entire structure.

 

[JAMIE MCG]

Don't believe everything you see on T.V.

Thanks SparticleBrane for working out the equation, and I'll stop spreading this lie, still they were only a few million pounds off still mind bottling when you think about air being that heavy

 

[SparticleBrane]

Definitely...the stuff is significantly heavy!
A set of double 130s, between 0psi and full, is a difference of almost 21lbs.

 

[The Kraken]

Ya know, every now and then, and so rarely, a thread comes along that is just absolutely delightful . . .

and this is one of them.

Thanx . . .

the K

 

[WarmWaterDiver]

If you raised the air pressure in the cylinder encapsulating the tower to 11.8 PSIG (the equivalent of 28 fsw depth) the compressed air would equal the weight of the entire structure given the figures above.

If you raised the pressure to 4.3 PSIG (about 10 fsw depth equivalent) it would equal the weight of the steel given the figures above.

Mythbusters just needed to top off the tank a bit . . .

I'm using 60 degrees Farenheit air temperature

 

[1982shawn]

I disagree with MythBusters.

Specifically...
The Eiffel Tower (including the spire) is 1,052ft tall and at it's widest point, 423ft wide.
Assuming a perfect cylinder (pi*[radius^2]*height), that's (pi)((423/2)^2) = 140,530.5 sq. ft. as the base, times 1,052ft for the height = 147,838,094.4cf inside the cylinder
At 0.08lbs/cf that's 11,827,047.55lbs of air. The metal in the tower weighs 7300 tons; if you include everything it's 10,100 tons. That's 14,600,000lb or 20,200,000lbs depending on if you want to include just the metal or the entire structure.

You forgot to pressurize the tank.
(Empty Volume/14.7psia)(max psi)= compressed volume
(147,838,094.4/14.7)(2400)"well say its an LP tank"
(10057013)(2400)=24136831738 cft of compressed air in the giant scuba tank
(24,136,831,738)(0.08)=1,930,946,539lbs of air, almost 2 billion pound of air!

 

[Steve_C]

Except of course the tower is very much not a cylinder so its volume is much less than the volume of a cylinder of the same height.
Probably come closer with a cone but even that over estimates since the sides are very much concave. So tbones calculation shows even if you widely over estimate the volume but fix the amount of steel myth busters is still way off.

 

[halocline]

I guess its a slow sports day today.