Atmospheric Pressure: Why is it Equal?

Click For Summary

Discussion Overview

The discussion revolves around the concept of atmospheric pressure and why it is considered equal in all directions. Participants explore the relationship between pressure, weight, and height in the context of gas behavior, addressing both theoretical and conceptual aspects.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants assert that pressure at the bottom of a gas volume is defined by its weight times the height, questioning the implications of this relationship.
  • Others challenge the validity of the claim that weight times height can represent pressure, noting that it does not have the correct units.
  • A participant clarifies that "pressure is equal in all directions" refers to the uniformity of pressure at a fixed location, independent of surface orientation.
  • Some participants suggest that the original statement about pressure may imply a correct understanding of the context, but still argue that the formulation is incorrect.
  • There is a discussion about the appropriate relationship for calculating pressure, with references to density and height, indicating a need for clarity in definitions used.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are competing views regarding the correct formulation of pressure and the implications of the original statement. Disagreement persists over the relationship between weight, height, and pressure.

Contextual Notes

Limitations include unresolved definitions of pressure and weight, as well as the dependence on the context of the discussion. The mathematical relationships presented are not fully agreed upon.

huyhohoang
Messages
12
Reaction score
0
Hello everyone!
As we've known, the pressure at the bottom of a volume of gas is define by its weight times the height. So I wonder why the atmospheric pressure is equal in all direction?
Many thanks
 
Physics news on Phys.org
huyhohoang said:
Hello everyone!
As we've known, the pressure at the bottom of a volume of gas is define by its weight times the height. So I wonder why the atmospheric pressure is equal in all direction?
Many thanks
Hi.
I don't understand what makes you think one thing has something to do with the other.
 
When we say that the "pressure is equal in all directions," what we mean is that, at a given fixed location, no matter which way you orient a surface upon which the pressure is acting, you get the same value for the pressure. So, we are not referring to changes in pressure with spatial location.
 
huyhohoang said:
Hello everyone!
As we've known, the pressure at the bottom of a volume of gas is define by its weight times the height.
This is not true. Weight times height doesn't even have the right units to be a pressure.
 
nasu said:
This is not true. Weight times height doesn't even have the right units to be a pressure.
I think the statement about it being "the bottom of a volume" implies the OP correctly understands it's over the surface area at the bottom of the column.
 
russ_watters said:
I think the statement about it being "the bottom of a volume" implies the OP correctly understands it's over the surface area at the bottom of the column.
But the result would still be wrong. Weight times height does not have units of force.
Density times height -- now that would have units of pressure -- at least if you measured density in force units.
 
jbriggs444 said:
But the result would still be wrong. Weight times height does not have units of force.
Density times height -- now that would have units of pressure -- at least if you measured density in force units.
Yeah - he shouldn't have said height at all since he already has the weight. Still is only tangential to the question he's asking, so probably not worth the extra few posts discussing it.
 
  • Like
Likes   Reactions: jbriggs444

Similar threads

High School Problem with understanding deriving Torricelli's law
  • · Replies 14 ·
Replies
14
Views
2K
Undergrad Atmospheric air pressure on the human body
  • · Replies 8 ·
Replies
8
Views
8K
High School Fully submerged block in a pool of water
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Water pressure affects air pressure
  • · Replies 9 ·
Replies
9
Views
4K
High School Strain on a foil sheet separating two compartments in a cylinder
  • · Replies 4 ·
Replies
4
Views
1K
Undergrad Is atmospheric pressure gravitational or kinetic?
  • · Replies 20 ·
Replies
20
Views
18K
High School Pressure of air inside a glass
  • · Replies 3 ·
Replies
3
Views
2K
High School Is water pressure on an inclined wall less than the weight of the water?
  • · Replies 31 ·
2
Replies
31
Views
2K
Undergrad Free fall of person in a sled to direct horizontal motion by atmospheric resistance
  • · Replies 12 ·
Replies
12
Views
1K
Graduate Optimal Size of Rocket Engine Nozzle for Vacuum Performance
  • · Replies 26 ·
Replies
26
Views
4K