Conceptual problems with pressure, me to clarify

In summary: However, the pressure at the bottom of the pipe will be much higher than the pressure at the top. This is because the atmospheric pressure is pushing down on the liquid in the pipe, but the atmospheric pressure is much less than the atmospheric pressure at the surface of the water.
  • #1
jenzao
48
0
Why is air pressure always factored in when calculating pressure at a given depth of water?
Why is the force from air pushing down on the surface of water the same at 1m as it is at 100m?
there is no air underwater, so why do we still need this value when doing pressure-depth calculations?
 
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  • #2
Total pressure at any depth in the water is sum of air pressure and water pressure. The air pressure at the surface, independent of depth, has to be added into get the total.
For a simple analogy, put a ten pound weight on a scale - it will read ten pounds. Put another ten pound weight on top of the first and the scale will read twenty pounds.
 
  • #3
The water must be able to sustain the weight of the air above it.

Thus, mathman's analogy is hardly just an analogy, rather, it is more of a precise description.

As I am sure he knows full well.
 
  • #4
this was explained really well, thank you. just quick follow-up.. Is gauge pressure simply pressure minus the air pressure? (101325Pa)?
 
  • #5
Yes.

Btw, air pressure is not the same at 1m as at 100m. Pilots use barometers (air pressure sensors) to measure their altitude.
 
  • #6
russ_watters said:
Btw, air pressure is not the same at 1m as at 100m. Pilots use barometers (air pressure sensors) to measure their altitude.

I'm sure (!? uh -ohh better to stop typing now) that he meant 1 meter or 100 meters depth.
 
  • #7
gmax137 said:
I'm sure (!? uh -ohh better to stop typing now) that he meant 1 meter or 100 meters depth.
I think he meant something like that, yes.

I quote:
Why is the force from air pushing down on the surface of water the same at 1m as it is at 100m?

This question makes no sense. There is no surface at 1m (depth?) or 100m. I'm guessing that you meant why you always have to add up the air pressure at the surface of the water whether we're talking about (total) pressures at 1m depth or 100m depth. I think the OP understands the answer already, but just to be sure. If you put three hamburgers on top of each other and you squash the top one, the bottom one will also get squashed, and not only the first (and second). :)

I'm hungry now.
 
  • #8
gmax137 said:
I'm sure (!? uh -ohh better to stop typing now) that he meant 1 meter or 100 meters depth.
Perhaps, but does it really matter...?

If you drop a closed 100m pipe into the water, you can still use a barometric altimeter in it.
 

Related to Conceptual problems with pressure, me to clarify

1. What are conceptual problems with pressure?

Conceptual problems with pressure refer to difficulties in understanding the underlying principles and applications of pressure in various scientific contexts. These can include misconceptions, gaps in knowledge, and challenges in connecting theoretical concepts to real-world scenarios.

2. How do conceptual problems with pressure affect scientific research?

Conceptual problems with pressure can significantly impact scientific research by hindering accurate data interpretation, limiting the development of new theories and models, and leading to faulty conclusions. It is crucial for scientists to address and clarify these issues to ensure the validity and reliability of their research.

3. Can you provide an example of a conceptual problem with pressure?

One example of a conceptual problem with pressure is the misconception that pressure always increases with depth in a fluid. While this is true for some fluids, it does not apply to all substances and can lead to errors in calculations and predictions. Scientists must clarify the specific conditions and properties that affect pressure in different systems.

4. How can scientists address conceptual problems with pressure?

Scientists can address conceptual problems with pressure by regularly reviewing and updating their understanding of pressure principles, staying current with research and advancements in the field, and collaborating with other experts to discuss and clarify any uncertainties. Additionally, clear communication and education about pressure concepts can help prevent misconceptions and promote accurate understanding.

5. Why is it necessary to clarify conceptual problems with pressure?

It is necessary to clarify conceptual problems with pressure to ensure the accuracy and validity of scientific research and to prevent the spread of misinformation. Clear understanding of pressure principles is crucial for various fields and industries, such as engineering, weather forecasting, and medical diagnostics. By addressing these issues, scientists can advance knowledge and promote more effective problem-solving and decision-making.

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