How much atmospheric pressure is exerted on the human body?

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I understand that this will vary from human to human, but how much weight is exerted, in total, on the average adult human body. It would be very much appreciated if the calculations can be shown. Thanks!
 

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  • #2
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You asked two different questions...

The average pressure exerted on the human body by the atmosphere is the average local atmospheric pressure. At sea level this is about 101kPa.

The average weight exerted on the human body by the atmosphere is the weight of the atmosphere above an individual. This is equal to the local pressure times the surface area facing up. I have seen the surface area on the top of a human head and shoulders estimated at .1 m2.

This gives a weight of 10.1 kN, or just a little over 1.1 ton.
 
  • #3
sophiecentaur
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how much weight is exerted, in total, on the average adult human body.
I suspect that you are looking for an answer to a question that has been given you or to settle an argument (?). The essence of what's going on is not really explainable in the terms of your question. It's really important to distinguish between Force (eg. weight) and Pressure (e.g. Newtons per square metre))
The 'weight force' of the Atmosphere on an object, acts inwards in all directions and is described as Atmospheric Pressure (which we all know). Our bodies are doing nothing particularly clever by balancing the inward pressure from the atmosphere with the internal outward pressure; everything does this. We have no strength to fight against atmospheric pressure so our internal pressure is basically the same as outside. It's the same for a mouse or an elephant; the pressures are balanced even though the total squashing forces are very different. Submarines, an exception, have rigid hulls which keep their internal pressure much lower than the outside water pressure.
The ambient pressure is 'right' for us (all animals) to breathe in enough Oxygen to keep alive and to stop us losing too much body fluid by evaporation etc. etc. But it's all to do with Pressure and not Weight of Atmosphere. In a space ship, the pressure is maintained with Pumps and doesn't involve the 'weight of a column of air'.

The net effect of the atmospheric pressure this is a very small upward Force. We experience Upthrust because we are immersed (Archimedes Principle) in a fluid (the air) in the same way that we experience (much more) upthrust when we are in water. The weight of displaced air will be something in the region of
-Volume displaced X density X g
= -80Λ-3 X 1.2 X 9.8N
=about -0.9N, which is the Upthrust Force. (Equivalent to the weight of 90g of water)
which would be measurable - but not easily because we would need to measure our weight also in a vacuum and compare the two values.
 
  • #4
I understand that this will vary from human to human, but how much weight is exerted, in total, on the average adult human body. It would be very much appreciated if the calculations can be shown. Thanks!
I guess what you really want to know is the total atmospheric force exerted on the human body. The average human body surface area is 1.73 m2 and the standard atmospheric pressure is 101,325 N/m2. Hence the total atmospheric force exerted on the average human body would be 1.73 m2 x 101,325 N/m2 = 175,300 N (approx.).

Assuming standard gravitational acceleration as 9.80665 m/s2, this would be equivalent to 175,300/9.80665 kgf = 17,900 kgf.

That's a lot of force acting on the body but it's all counterbalanced by the internal pressure of the body and so you won't feel it at all. Hope this is the real answer you're looking for.
 
  • #5
Keith_McClary
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The average human body surface area is 1.73 m2
I was going to give a spherical cow answer.
 
  • #6
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I guess what you really want to know is the total atmospheric force exerted on the human body. The average human body surface area is 1.73 m2 and the standard atmospheric pressure is 101,325 N/m2. Hence the total atmospheric force exerted on the average human body would be 1.73 m2 x 101,325 N/m2 = 175,300 N (approx.).

Assuming standard gravitational acceleration as 9.80665 m/s2, this would be equivalent to 175,300/9.80665 kgf = 17,900 kgf.

That's a lot of force acting on the body but it's all counterbalanced by the internal pressure of the body and so you won't feel it at all. Hope this is the real answer you're looking for.
This is not correct, because the pressure force on a surface is normal to the surface, and, these normal forces on the body must be added vectorially. If you do this correctly, as was done by @mfig, you get the answer he gave.
 
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This is not correct, because the pressure force on a surface is normal to the surface, and, these normal forces on the body must be added vectorially. If you do this correctly, as was done by @mfig, you get the answer he gave.
Sorry, have to disagree with you. Don't forget, the atmospheric pressure acts upwards as well via all the downward facing surfaces and the NET force would be zero. However, the pressures at the top of the body are slightly lower than at the bottom due to the weight of the air resulting in a small upward force (0.9N) as calculated by sophiecentaur.

But I suspect that Hunter1234 is more interested in the total force that would be crushing the human body if it had been hollow and filled with nothing, ie a vacuum, akin to the submarine deep under the ocean. That was what I was trying to calculate for him.

So I guess the answer really depends on what Hunter1234 is actually asking.

Don't forget, I'm not Bill Nye.
 
  • #8
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Sorry, have to disagree with you. Don't forget, the atmospheric pressure acts upwards as well via all the downward facing surfaces and the NET force would be zero. However, the pressures at the top of the body are slightly lower than at the bottom due to the weight of the air resulting in a small upward force (0.9N) as calculated by sophiecentaur.

But I suspect that Hunter1234 is more interested in the total force that would be crushing the human body if it had been hollow and filled with nothing, ie a vacuum, akin to the submarine deep under the ocean. That was what I was trying to calculate for him.

So I guess the answer really depends on what Hunter1234 is actually asking.

Don't forget, I'm not Bill Nye.
I respectfully disagree. The forces have to be added vectorially, in my humble judgment. I guess we'll just have to agree to disagree.
 
  • #9
sophiecentaur
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But I suspect that Hunter1234 is more interested in the total force that would be crushing the human body if it had been hollow and filled with nothing, ie a vacuum, akin to the submarine deep under the ocean. That was what I was trying to calculate for him.
I suspect that you are right about what Hunter 'thinks' he wants to know. But the Force is really of no consequence unless we want to know about bouyancy. The effects of pressure on the human body are not so much Mechanical but Chemical. A human can 'breathe' air in and out at more or less any ambient pressure. The problem arises when the partial pressures of gases in the air (and also within the body) are 'inappropriate' for respiration and the rates of gaseous exchange do not sustain life. (That's why saturation divers use special mixes of gases.)
The Force involved is little more than a naive concept that is brought into things by non-scientists because the 'numbers' look impressive.
 
  • #10
jbriggs444
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I guess what you really want to know is the total atmospheric force exerted on the human body. The average human body surface area is 1.73 m2 and the standard atmospheric pressure is 101,325 N/m2. Hence the total atmospheric force exerted on the average human body would be 1.73 m2 x 101,325 N/m2 = 175,300 N (approx.).

Assuming standard gravitational acceleration as 9.80665 m/s2, this would be equivalent to 175,300/9.80665 kgf = 17,900 kgf.

That's a lot of force acting on the body but it's all counterbalanced by the internal pressure of the body and so you won't feel it at all. Hope this is the real answer you're looking for.
The lungs have a lot of surface area. Why not count that? Since the question is nonsensical, the answer should be as well.
 
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  • #11
256bits
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But I suspect that Hunter1234 is more interested in the total force
If you squeeze an object between your hands, do you add the 10N from the left hand with the 10N from the right hand to get 20N of total force?
 
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  • #12
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Now what would this be for the same human who (unwisely) stepped out of his space capsule unprepared on the surface of Venus?
 
  • #13
sophiecentaur
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Now what would this be for the same human who (unwisely) stepped out of his space capsule unprepared on the surface of Venus?
Chemical or Thermal effects would be felt first. Secondly, the different pressure could be 'noticeable' but I doubt it.
 

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