Atmospheric pressure- where do we get the mass?

[opus]

How can we lose pressure if the pressure is already equal inside and out?

What do you feel in your ears when you drive up a mountain, fly up in a plane or dive deep under water?

Good point. So then we wouldn't lose pressure because the pressure is equal on both sides. I suppose then, and this may be for another topic, what are the causes of our pressurization? A google search led me to things like cabin pressurization which isn't exactly what I'm looking for.

What do you feel in your ears when you drive up a mountain, fly up in a plane or dive deep under water?

That would be pressure from the change in ambient pressure which could be experienced from either going up (decrease in pressure) or down (increase in pressure).

 

[russ_watters]

Good point. So then we wouldn't lose pressure because the pressure is equal on both sides. I suppose then, and this may be for another topic, what are the causes of our pressurization?

You answered this question correctly in your own first post. I feel like you are looking for a complicated answer to a simple question you already know the answer to. Consider the following:

A. You set a 15 lb stack of books on a table. How much force does it apply to the table?
B. You take half the books off. How much force does the stack apply to the table now?
1. You set a 15 lb stack of books on top of a plastic bag full of water on top of a table. What is the force applied to the bag of water?
2. You take half the books off. What is the force applied to the bag of water now?
X. You have a glass of water at sea level (round off to 15 psi atmospheric pressure). What is the pressure inside the glass of water?
Y. You take the glass up to an altitude where atmospheric pressure is half sea level. What is the pressure inside the glass of water now?

None of these are trick questions and all three sets of scenarios are the same. What happens to change from the first to the second question in each set of scenarios?

 

[opus]

In the second cases, you are removing weight, or pressure, from the top. In the first two scenarios its by removing books, in the last it's removing some amount of column of air from atop the glass. I think I've been looking for a deeper, more complicated answer for no reason as you've said. Sorry about that.

 

[Charles Link]

On the gas pressure inside of us, on a previous comment above, did you ever see them talk on TV about deep sea divers need to make sure they don't come to the surface too quickly or they can get the "bends", a problem caused by gases "boiling" out of their body etc, because the internal gas pressure increased when they were in the higher pressure environment farther down, etc., and they need to release this extra pressure slowly? See https://en.wikipedia.org/wiki/Decompression_sickness

 

[opus]

On the gas pressure inside of us, on a previous comment above, did you ever see them talk on TV about deep sea divers need to make sure they don't come to the surface too quickly or they can get the "bends", a problem caused by gases "boiling" out of their body etc, because the internal gas pressure increased when they were in the higher pressure environment farther down, etc., and they need to release this extra pressure slowly? See https://en.wikipedia.org/wiki/Decompression_sickness

Yes as I understand it, the gases don't have time to be exhaled as they come out of solution too quickly and small bubbles come into formation inside the body. Are these gases the cause for our pressurization?

 

[Charles Link]

Yes as I understand it, the gases don't have time to be exhaled as they come out of solution too quickly and small bubbles come into formation inside the body. Are these gases the cause for our pressurization?

These gases are a result of the pressurization. These gases, mostly dissolved, are also present at 1 atmospheric pressure.

 

[russ_watters]

In the second cases, you are removing weight, or pressure, from the top. In the first two scenarios its by removing books, in the last it's removing some amount of column of air from atop the glass. I think I've been looking for a deeper, more complicated answer for no reason as you've said. Sorry about that.

No prob - it's common to overcomplicated these things. One follow-up though:

I think the reason for this confusion is that you have the impression that the pressure needs to somehow be "relieved". This is only true for rigid containers. The human body is not a rigid container, it's just a flexible bag of water.

...unless you have a sinus or ear infection...

 

[DaveC426913]

...what are the causes of our pressurization?

What do you mean? Under what circumstances? You mean like in regular life?

 

[Charles Link]

@opus One item that might help you to understand gas pressure is to look at the pressure in a couple of ways: The atmospheric pressure is caused by the weight of the column of air above us, all the way to the outer atmosphere. If you consider a spaceship outside the Earth's atmosphere, it doesn't have the weight of the column of air, but it needs to have the inside air pressure maintained by having sufficient air inside to create an internal pressure, following the ideal gas equation $PV=nRT$. If there are sufficient number of gas particles at a given temperature, the pressure is automatically created. The spaceship needs to be able to withstand this internal pressure with very solid (perhaps somewhat elastic) walls or it could easily rupture and come apart. Outside the spacecraft , there is no external air pressure to balance the internal pressure.

 

[DrDu]

That's because a weight will not only increase pressure but also strain. The volume of you hand practically does not change. It is the deformation of your hand, that you feel. You can feel pressure changes in an airplane or when diving, because the volume of the gas in your body changes. Once you do pressure accomodation, you won't note the pressure change.

 

[opus]

No prob - it's common to overcomplicated these things. One follow-up though:

I think the reason for this confusion is that you have the impression that the pressure needs to somehow be "relieved". This is only true for rigid containers. The human body is not a rigid container, it's just a flexible bag of water.

...unless you have a sinus or ear infection...

Yes I suppose that has been a problem for me as there are certain examples that I try to think of that aren't exactly the same. For example, increasing the temperature of a full SCUBA tank would increase the pressure and not the volume because it's a steel container. But if we did the same thing to a flexible balloon, it would be able to expand and increase it's volume to maintain the same pressure.

What do you mean? Under what circumstances? You mean like in regular life?

Yes my original confusion lied in the uncertainty in how the human body was pressurized to "push back" against the outside 14.7 psi for the equilibrium.

@opus One item that might help you to understand gas pressure is to look at the pressure in a couple of ways: The atmospheric pressure is caused by the weight of the column of air above us, all the way to the outer atmosphere. If you consider a spaceship outside the Earth's atmosphere, it doesn't have the weight of the column of air, but it needs to have the inside air pressure maintained by having sufficient air inside to create an internal pressure, following the ideal gas equation $PV=nRT$. If there are sufficient number of gas particles at a given temperature, the pressure is automatically created. The spaceship needs to be able to withstand this internal pressure with very solid (perhaps somewhat elastic) walls or it could easily rupture and come apart. Outside the spacecraft , there is no external air pressure to balance the internal pressure.

So if we left the surface of the Earth, and our cockpit was pressurized to 1 ata, once we got out of the atmosphere, we would have 14 pounds of outward pressure per square inch, but nothing on the outside to push back and balance it out. Sounds like potential for a big explosion!

 

[DaveC426913]

Yes my original confusion lied in the uncertainty in how the human body was pressurized to "push back" against the outside 14.7 psi for the equilibrium.

Ok, you're clear on that now though, yes?

Anything made on Earth (including babies) will have 1 atmosphere of pressure - unless there's a cause for it to be otherwise (lower pressure or higher pressure).

 

[opus]

Ok, you're clear on that now though, yes?

Anything made on Earth (including babies) will have 1 atmosphere of pressure - unless there's a cause for it to be otherwise (lower pressure or higher pressure).

I am indeed. Thank you!