Talk:Hydrostatics

Hydrostatic pressure

The "hydrostatic pressure" section makes zero sense, and I'm not just talking about the grammar. Can someone fix it? Piercetheorganist 00:51, 2 July 2007 (UTC)

It's also a shame that such an important topic has no article of its own, just redirects to this bad sub-section. I'm not qualified to write an article, but at least in medicine it's important enough to merit its own, decent article. - Draeco (talk) 05:12, 16 January 2008 (UTC)

I don't believe it should have it's own article as this essentially is it's article. Splitting hydrostatics off really wouldn't leave much for this article to cover in its own right. Iron_Engineer (talk) 20:20, 30 June 2009 (UTC)

Weight of water

Someone[1] or two people[2] have changed the article to say that

“ Considering a small cube of liquid at rest below a free surface, pressure caused by the height of the liquid above must be balanced by a resisting pressure in this small cube. For an infinitely small cube the stress is the same in all directions and liquid weight or equivalent pressure can be expressed as... ”

However, I was under the impression that, because pressure is Force over area, pressure was thus caused by a force acting over an area, the force being the weight of the water in this case. Is this not the case? --M1ss1ontomars2k4 (talk) 00:27, 24 March 2008 (UTC)

This is somewhat true. What everyone, including the article seems to be forgetting, however, is that this weight of the water creates the pressure gradient within the fluid. In statics, the pressure increases with depth because of gravity. However, it also increases in any kind of potential gradient. If an EM field is placed across water and the fluid was completely static, there would still exist a pressure gradient. Thus higher pressure could exist on the left of a cube than on the right. Also, a box of water can be pressurized, increasing the hydrostatic pressure. Thus the pressure is not just related to the depth. Iron_Engineer (talk) 18:57, 30 June 2009 (UTC)

I just cleaned up the hydrostatics section a bit. Generalized it to include other statics situations other than gravitational and made it more accurate in terms of variable pressures and a varying gravitational field. Iron_Engineer (talk) 20:18, 30 June 2009 (UTC)

A graphic would go a long way to explain stability.

Rotational stability depends on the relative lines of action of forces on an object. The upward buoyant force on an object acts through the centre of buoyancy, being the centroid of the displaced volume of fluid. The weight force on the object acts through its center of gravity. An object will be stable if an angular displacement moves the line of action of these forces to set up a 'righting moment'.

A couple of diagrams showing a canoe verses a coal barge and explaining the line of action, would help us stay dry. Please don't take as a complaint, I think your doing an important job. Thanks. Art. —Preceding unsigned comment added by 24.190.246.208 (talk) 22:12, 1 November 2008 (UTC)

History

The person named in this section as creating the fluid statics field is wrong. Hydrostatics dates back to Archimedes. He wrote several papers on fluid mechanics which are still being recovered. His entire theory of buoyancy is based on hydrostatics as well. He didn't just find out oh, things float. He actually determined the pressure gradient relation to depth and speculated on why. I believe he even quantified it in some papers recovered from that era but I don't have any sources for that. Iron_Engineer (talk) 20:18, 30 June 2009 (UTC)

Stability

I feel this should be moved to buoyancy. It just doesn't relate to the theory of fluid statics. This topic arises when discussing a system, most notably a ship, subjected to buoyant forces. This article is targeted at the theory of static fluid mechanics. Ultimately, stability is an area associated with dynamic system analysis that arises from a separate area of investigation than static fluids. I would like someone to respond before I move it but that doesn't seem likely as the previous message is dated to almost a year ago. —Preceding unsigned comment added by Iron Engineer (talk • contribs) 08:08, 1 July 2009 (UTC) I feel it is important. A natural gas well ....... it should stay were it's at.

Hydrostatic paradox

Hydrostatic paradox redirects here, but is not explained. It should get either a section or an article of its own. Paradoctor (talk) 12:32, 28 July 2009 (UTC)

style

Please: WP:MOSMATH exists. I found this:

z-z₀

I changed it to this:

z − z₀

• Clearly the "0" should not be italicized.
• A minus sign should be used; not a hyphen.
• A space should precede and follow the minus sign.

Michael Hardy (talk) 00:37, 10 August 2012 (UTC)

Rest? You've got to be kidding

I think the term thrown around here for statics, namely rest is conflating the term. Fluids are not at rest like solids are. Their intermolecular motion is far from being "at rest." Is there a more formal way of specifying static fluids than saying that they are simply at rest? I'd like to remove that word in favor of something akin to describing their bulk motion in relation to their container having a zero average velocity. That is quite a lengthy replacement for being "at rest" but I prefer its specificity. I stopped thinking of liquids and gasses as being at rest pretty early in my studies. To say it now seems pretty juvenile. Fluids can be static, but never at rest! I like to saw logs! (talk) 10:58, 22 January 2015 (UTC)

Can u review the edit: diff ??
The wikipedia page for Hydrostatic equilibrium states the same thing: "fluids at rest" - but that page can be improved later. For the time being, i hope that a proper term is used at least in this article. Also, the citation i gave (of wikibooks, dont know if that counts as a valid citation) states hydrostatic eqm in more precise terms. You might also want to check that out. Awaiting reply :) Yashpalgoyal1304 (talk) 06:59, 1 April 2021 (UTC)

Shape of the infinitesimal

PraanWiki, 94.227.129.49 The current explanation is based on a cube. If you wish to change it to another geometry please consider the effects on the rest of the text and propose the complete alternative text here. · · · Peter (Southwood) ^(talk): 12:45, 22 March 2018 (UTC)

Proof of isotropy of pressure in a static fluid

In Section 2: Pressure in fluids at rest, in the first paragraph, it is stated:

"If a point in the fluid is thought of as an infinitesimally small cube, then it follows from the principles of equilibrium that the pressure on every side of this unit of fluid must be equal."

I find that it is unclear what is meant with "principles of equilibrium". If the original author meant that the total force acting on the cube must vanish, then this demonstration only shows that the pressure on opposite sides must be equal. On the other hand, if the author meant something else, maybe related to the microscopic origin of pressure, then this should be clarified. In the first case, I would propose to use a proof that considers the forces acting on an infinitesimal wedge of fluid. Now the requirement that the net force vanishes relates the pressure in different directions (not just opposite directions) which shows that the pressure is a scalar quantity. PraanWiki 16:30, 22 March 2018

Reply to user Pbsouthwood comment: the shape of the infinitesimal in the rest of the text (section on hydrostatic pressure) is not related to the proof of the isotropy of pressure. It might be favourable to also change that part of the text. It is easy to show that the net force on an infinitesimal cube due to the fact that the pressure is not homogeneous is given by the gradient of the pressure. In equilibrium the total force is zero and for external conservative forces that work on the cube (such as gravity) this gives the main differential equation of hydrostatics. This can then be integrated to give the same result for the variation of the pressure with depth as is shown now. PraanWiki 16:50, 22 March 2018

PraanWiki. Please sign your talk page edits with four tildes (~~~~), and continue a discussion under the same heading where it was started, that way people can know that you are who you say you are, and keep track of the discussion.

If you have a better explanation (note that we do not technically require a proof, as this is an encyclopedia, not a textbook), please feel welcome to lay it out on this page in detail, so it can be compared with the existing content. If there is consensus that it is better, then it can be copied in to replace the current text. Bear in mind that our readership comes from all levels of technical education, and try to keep the explanation at least as accessible as the current version. Cheers, · · · Peter (Southwood) ^(talk): 10:03, 23 March 2018 (UTC)

Disam/clarf suggestion

Add diff with hygrostatics? Ema--or (talk) 23:29, 18 February 2021 (UTC)

hydrostatic pressure

• what is z' here?? is it dz/dt ??
• can some consistency be brought in the expression here, and on/with other pages?? like
  • Free_surface#Rotation
  • Hydrostatic_equilibrium#Derivation_from_force_summation
  • Fluid_Mechanics/Analysis_Methods#Hydrostatics on wikibooks Yashpalgoyal1304 (talk) 07:56, 1 April 2021 (UTC)

Wiki Education assignment: 4A Wikipedia Assignment

This article was the subject of a Wiki Education Foundation-supported course assignment, between 21 August 2023 and 16 December 2023. Further details are available on the course page. Student editor(s): Beastkiller6142 (article contribs). Peer reviewers: ThomasDLV, Alana1132.

— Assignment last updated by Kmijares (talk) 22:40, 15 November 2023 (UTC)

Hydrostatics is a subcategory of fluid statics?

The initial statement 'Fluid statics or hydrostatics is ...' implies that fluid statics and hydrostatics are the same, but then 'hydrostatics is a subcategory of fluid statics ...' contradicts that. The latter statement seems to imply that hydrostatics is restricted to incompressible fluids (which makes sense given that 'hydro' is from the Greek word for water), but I don't see that stated in other articles or in the quoted Merriam-Webster definition. WRJF (talk) 11:47, 2 November 2023 (UTC)

My view is that hydrostatics is a sub-category of fluid statics. Hydrostatics is confined to liquids, and aerostatics is confined to gases. (Fluids are all materials that aren't solids; so liquids and gases are fluids.) The science of lighter-than-air balloons such as hydrogen and helium balloons, and hot-air balloons, can be described as aerostatics.

The distinction is similar to the distinction between aerodynamics and hydrodynamics as the two halves of fluid dynamics. Dolphin (t) 12:44, 2 November 2023 (UTC)