How much atmospheric pressure is exerted on the human body?

In summary, the total atmospheric force exerted on the average adult human body is approximately 175,300 Newtons, or 17,900 kilograms of force. This is due to the standard atmospheric pressure of 101,325 N/m2 and the average human body surface area of 1.73 m2. However, this force is counterbalanced by the internal pressure of the body, so it is not felt. The pressure force on a surface is normal to the surface and the normal forces on the body must be added vectorially. The net effect of the atmospheric pressure is a small upward force of 0.9 Newtons. It is important to distinguish between force and pressure when discussing the weight of the atmosphere on the human body
  • #1
11
1
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!
 
  • Like
Likes alemario
Physics news on Phys.org
  • #2
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
Hunter1234 said:
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
Hunter1234 said:
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
NotBillNye said:
The average human body surface area is 1.73 m2
I was going to give a spherical cow answer.
 
  • #6
NotBillNye said:
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.
 
  • Like
Likes 256bits and sophiecentaur
  • #7
Chestermiller said:
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
NotBillNye said:
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
NotBillNye said:
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
NotBillNye said:
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.
 
  • Like
Likes phinds, Bystander and russ_watters
  • #11
NotBillNye said:
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?
 
  • Like
Likes nasu and Chestermiller
  • #12
Now what would this be for the same human who (unwisely) stepped out of his space capsule unprepared on the surface of Venus?
 
  • #13
ras said:
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.
 
  • #14
Hunter1234 said:
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!
Atmospheric Pressureforce exerted by the weight of the air
Atmospheric pressure is defined as the force per unit area exerted against a surface by the weight of the air above that surface. In the diagram below, the pressure at point "X" increases as the weight of the air above it increases. The same can be said about decreasing pressure, where the pressure at point "X" decreases if the weight of the air above it also decreases.

def1.gif

Thinking in terms of air molecules, if the number of air molecules above a surface increases, there are more molecules to exert a force on that surface and consequently, the pressure increases. The opposite is also true, where a reduction in the number of air molecules above a surface will result in a decrease in pressure. Atmospheric pressure is measured with an instrument called a "barometer", which is why atmospheric pressure is also referred to as barometric pressure.
def2.gif
In aviation and television weather reports, pressure is given in inches of mercury ("Hg), while meteorologists use millibars (mb), the unit of pressure found on weather maps.
As an example, consider a "unit area" of 1 square inch. At sea level, the weight of the air above this unit area would (on average) weigh 14.7 pounds! That means pressure applied by this air on the unit area would be 14.7 pounds per square inch. Meteorologists use a metric unit for pressure called a millibar and the average pressure at sea level is 1013.25 millibars.
Ref;
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/prs/def.rxml
 
  • Like
Likes Delta2
  • #15
This thread is 5 years old...
 
  • Like
Likes sophiecentaur
  • #16
russ_watters said:
This thread is 5 years old...
I don't see what's the problem with that really. Chestermiller and the others are still around and can answer if they find the new reply interesting. The nice thing with electronic threads is that there is no paper yellowed out, no ink worn out, the thread appears as good as new.
 
  • #17
russ_watters said:
This thread is 5 years old...
But the atmosphere is much the same. :wink:
 
  • Haha
  • Like
Likes vanhees71, russ_watters, Filip Larsen and 1 other person

1. How is atmospheric pressure measured?

Atmospheric pressure is typically measured using a barometer, which measures the force exerted by the weight of the air above it. The most commonly used unit for atmospheric pressure is the pascal (Pa), but it can also be measured in other units such as millibars (mb) or inches of mercury (inHg).

2. What is the average atmospheric pressure on the human body?

The average atmospheric pressure at sea level is 1013.25 hPa or 14.7 psi. This is the amount of pressure that is exerted on the human body when standing at sea level.

3. How does atmospheric pressure affect the human body?

Atmospheric pressure affects the human body in various ways. At high altitudes, where atmospheric pressure is lower, the body may experience symptoms such as shortness of breath and fatigue due to the decreased amount of oxygen in the air. At deeper depths, where atmospheric pressure is higher, the body may experience the effects of increased pressure, such as nitrogen narcosis and decompression sickness in scuba divers.

4. Can the human body withstand extreme atmospheric pressure?

The human body is capable of withstanding a wide range of atmospheric pressures. However, extreme changes in pressure, such as sudden increases or decreases, can be dangerous and even fatal. The body is able to adapt to gradual changes in pressure, such as those experienced during airplane flights or scuba diving, but it may not be able to withstand sudden changes in pressure.

5. How does atmospheric pressure vary at different altitudes?

Atmospheric pressure decreases with increasing altitude. This is because there is less air above the body to exert pressure. For every 1000 meters increase in altitude, atmospheric pressure decreases by about 11%.

Suggested for: How much atmospheric pressure is exerted on the human body?

Replies
12
Views
231
Replies
8
Views
6K
Replies
14
Views
1K
Replies
8
Views
912
Replies
1
Views
1K
Replies
7
Views
3K
Replies
20
Views
16K
Replies
3
Views
715
Replies
4
Views
672
Back
Top