Atmospheric pressure per square cm

In summary: The area of a square with sides of length 2 cm would be 4cm^2.In summary, the conversation discusses the confusion over calculating areas and using units of kg/cm^2 for pressure. It is noted that using Pascals (N/m^2) is more accurate. The difference between a square with sides of length 2 cm and an area of 2 cm^2 is clarified, and the misconception of describing quadratic growth as exponential is addressed. The conversation also mentions the ambiguity of the English language in describing areas and provides a link to an article discussing this issue.
  • #1
Theg
11
0
Hi, I have a problem to understand one small thing. They say that air pressure per square cm at sea level is approximately 1 kg.
So at 2 sq cm it will be 2 kg, at 3 sq cm it will be 3 kg etc.
But... Here where I have a problem. The thing is that inside 2 square cm you can put 4 one square cm. Inside 3 square cm you can put nine square cm.
Just look at it this way:
2sq= 4= 1sq+1sq+1sq+1sq
3sq= 9 =
1sq+1sq+1sq+1sq+1sq+1sq+1sq+1sq+1sq
You see? So according to this logic the air pressure supposed to grow exponentially when you increase the surface, but according to textbooks it's not. Why?
It's supposed to be 1 kg at 1 sq cm, 4 kg at 2 sq cm, 9 kg at 3 cm etc.
See my trouble?
 
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  • #2
Denoting pressures in units of kg/cm^2 is done but it is sloppy; use Pascals (N/m^2) instead.

Your confusion over area is not uncommon, people say "two centimeters square" meaning, a square with sides of length 2 cm. This has an area of four square centimeters (4 cm^2). An area of 2 cm^2 would be a square with sides of length 1.414 cm (because 1.414 * 1.414 = 2).
 
  • #3
Pressures in units of kg/cm^2 is sloppy because it assumes you are located somewhere (like the surface of the earth) where gravitational acceleration is 9.8 m/sec^2
 
  • #4
gmax137 said:
Denoting pressures in units of kg/cm^2 is done but it is sloppy; use Pascals (N/m^2) instead.

Your confusion over area is not uncommon, people say "two centimeters square" meaning, a square with sides of length 2 cm. This has an area of four square centimeters (4 cm^2). An area of 2 cm^2 would be a square with sides of length 1.414 cm (because 1.414 * 1.414 = 2).
Ohh so you say my mistake is how I calculate square area? So an area of 2cm^2 isn't equale to a square with sides of length 2 cm?
 
  • #5
Theg said:
an area of 2cm^2 isn't equale to a square with sides of length 2 cm?

Correct. As you said in your first post, a square with sides of length 2 cm has an area of 4 cm^2.

There is a difference in the written words:
"an area of (two cm), squared"
"an area of two (cm squared)"

Confusing? Yes. This is a problem with English, I don't know if other languages are also ambiguous in this way.
 
  • #6
In the past we used to say "two square cms" and the convention still applies when we buy carpet or tiles in square metres. Using "two cm2" took its place in Science and I am not sure it helped at all.
 
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  • #7
By the way, one complaint (sorry to nitpick, but this is a pet peeve of mine). If something grows as the square (i.e. 1 kg for a 1 cm square, 4 kg for a 2 cm square, 9kg for a 3 cm square...), this is growing quadratically, not exponentially. It has become common practice for people to describe anything that grows faster than linear as "exponential". Exponential growth is faster than any power (faster than x^2, faster than x^3, faster than x^4...).

It turns out I'm not the only one that is bothered by this:

https://www.nytimes.com/2019/03/04/opinion/exponential-language-math.html
 
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  • #8
Theg said:
Ohh so you say my mistake is how I calculate square area? So an area of 2cm^2 isn't equale to a square with sides of length 2 cm?
Correct. 2cm^2 would be the area of a rectangle 2cm * 1cm.
 

1. What is atmospheric pressure per square cm?

Atmospheric pressure per square cm, also known as surface pressure, is the force exerted by the weight of the Earth's atmosphere on a unit area at sea level. It is typically measured in units of pounds per square inch (psi) or millibars (mb).

2. How is atmospheric pressure per square cm measured?

Atmospheric pressure per square cm is measured using a device called a barometer. A common type of barometer is a mercury barometer, which uses a column of mercury to measure the pressure exerted by the atmosphere. Other types of barometers include aneroid barometers and electronic barometers.

3. What factors affect atmospheric pressure per square cm?

The main factors that affect atmospheric pressure per square cm are altitude, temperature, and weather conditions. As altitude increases, atmospheric pressure decreases. As temperature increases, atmospheric pressure also increases. Changes in weather, such as the presence of high or low pressure systems, can also affect atmospheric pressure.

4. What are the units of measurement for atmospheric pressure per square cm?

The most commonly used units for measuring atmospheric pressure per square cm are pounds per square inch (psi) and millibars (mb). Other units that may be used include inches of mercury (inHg) and kilopascals (kPa).

5. Why is atmospheric pressure per square cm important?

Atmospheric pressure per square cm is important because it plays a crucial role in weather patterns and climate. It also affects the behavior of gases and liquids, as well as the functioning of living organisms. Changes in atmospheric pressure can also indicate changes in weather conditions, which can impact human activities and safety.

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