What is Hydrostatic: Definition and 241 Discussions

Fluid statics or hydrostatics is the branch of fluid mechanics that studies "fluids at hydrostatic equilibrium and the pressure in a fluid or exerted by a fluid on an immersed body".It encompasses the study of the conditions under which fluids are at rest in stable equilibrium as opposed to fluid dynamics, the study of fluids in motion. Hydrostatics is a subcategory of fluid statics, which is the study of all fluids, both compressible or incompressible, at rest.
Hydrostatics is fundamental to hydraulics, the engineering of equipment for storing, transporting and using fluids. It is also relevant to geophysics and astrophysics (for example, in understanding plate tectonics and the anomalies of the Earth's gravitational field), to meteorology, to medicine (in the context of blood pressure), and many other fields.
Hydrostatics offers physical explanations for many phenomena of everyday life, such as why atmospheric pressure changes with altitude, why wood and oil float on water, and why the surface of still water is always level.

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  1. lost captain

    I Hydrostatic pressure inside an inverted tube

    When we learn about atmospheric pressure in physics class, there's this classic experiment with a straw (second drawing). So i wanted to ask about the hydrostatic pressure in that particular experiment. Is the total pressure at point 1' equal to Patm + ρgh ? So is the total pressure at point 1'...
  2. DIYEngine235

    Automotive Poor Man's Hydrostatic drive: power steering pump as motor?

    I'm toying with the idea of building a UTV/ATV using parts from an old John Deere 210 lawn tractor. The main design problem I have is I need to reconfigure the motor relative to the transaxle. The transaxle is a 4 speed Peerless 2300 with reverse. Because of the shift arm location, I have to...
  3. JABAS

    B Hydrostatic pressure on top of a cone filled with water

    Does the cone shape and extra water below the colum of water of 1 cm increase the pressure/vacuum effect at "B" or "A"? Is it simular to an inverted cone dependant on angle of sides of cones, when looking for pressure at the bottom of a cone or cylinder? In simple terms, how? Basic maths only...
  4. R

    Hydrostatic pressure in a narrow container

    I understand that pressure increases with depth regardless of the shape of the container. However, this doesn't sit well with me. Imagine a container: 8' tall x 1" wide x 1' long. The pressure at the bottom of the container is 8' x 62.4 pcf = 499.2psf. However, the weight of the water in the...
  5. Induana

    B Hydrostatic pressure in a bottle of water on ISS

    Hello, I am new in physics but I really like it so far. I have a question about hydrostatic pressure. I know that hydrostatic pressure equals (height)x(density)x(g). Am I right if I say that hydrostatic pressure in a bottle of water on ISS (state of weightlessness) will be zero ? Thank you for...
  6. S

    Hydrostatic pressure at a point inside a water tank that is accelerating

    I draw this diagram: The formula for hydrostatic pressure is: ##P=\rho g h## so I just plug everything $$P=1000 \times 9.8 \times 0.1=980 Pa$$ Will the acceleration of the cart affect the hydrostatic pressure? Another thing that came to my mind was there would be extra force coming from...
  7. FEAnalyst

    Stress in rectangular vessel subjected to hydrostatic pressure

    Hi, it's not easy to find formulas for stress in rectangular pressure vessels. However, I've found some in a Polish book titled "Podstawy konstrukcji aparatury chemicznej" (Fundamentals of the design of chemical process equipment) by J. Pikon. The problem is that the book provides equations for...
  8. M

    Construction How do you build a self-submersible boat?

    So I've been thinking for a long time now about making a self-submersible boat out of a plastic bottle without electronics. It should resurface by itself after a few minutes. I was thinking that it might increase its volume. By slowly dropping weights down the bottle and opening flaps on the...
  9. H

    Engineering Hydrostatic Pressure of Ball Floating in Liquid

    Let's say there's an object floating in liquid. The depth of the object below the surface is 𝑑 and its height above the water is ℎ. The density of the ball is 𝑝𝑏 and the density of the liquid is 𝑝𝐿. The pressure above the water is 𝑃𝑎𝑡𝑚. I understand this situation when only the density of the...
  10. U

    Comparing hydrostatic forces at the bottom of these 3 containers

    hello all , 1st and 2 nd water containers sit on ground and 3rd type of water container sit on fixed support along X axis and bottom parts are suspended in air , pls see picture , the drawing is half cross sections of cylinders All water level heights H and tubes D diameter are same ...
  11. C

    Hydrostatic Problem: Hinged water gate at the bottom of a reservoir

    My son and I are having a problem with part c that suggests our answer for part a and b are wrong.. Part a). If we've understood the teaching notes correctly the force on the gate acting through its centroid perpendicular to the gate and is given by F = ρgAd where ρ is the density of water...
  12. A

    Selecting hydraulic motors and a pump for hydrostatic transmission

    So I'm trying to make a GoKart that utilizes a hydraulic drive for the front two wheels and a mechanical driveshaft for the back two wheels but my main questions are selecting the motors and pumps. I just want to clarify a few things since I'm not sure if I did my math right. The max RPM for...
  13. Andrea Vironda

    Understanding the Principle of Dampening in Hydrostatic Systems

    Hi, In some hydrostatic tables I can see many spring-shaped pipes that are traversed by oil. Spring is responsible for a kind of dampening that I ignore how to deal with. Do you have any idea of the physical principle behind it?
  14. A

    Hydrostatic pressure of liquid in a cart on an inclined ramp

    Sorry for my English, I'm Spanish. I am not able to make the force diagram for the liquid. I am still in high school and started now little hydrostatic. If someone can give me a light, I would be very .grateful.
  15. J

    Engineering Hydrostatic Pressure Sluice Gate - Civil Engineering

    Please can you help with a question I am struggling with. I have done as much working out as I could until I was completely stumped: Calculate the concrete volume that is required to keep the sluice gate AB closed, assuming that the only resisting force is the friction between the concrete...
  16. S

    Compressed air pressure vs hydrostatic pressure

    Hi all, I'm new on here and will start off with what I think is a simple clarification. I'm questioning my workings due to previous work being completed by another engineer and thought this was the best place to ask. Essentially we have compressed air being supplied through a hose, the hose...
  17. T

    Finding the magnitude of the hydrostatic force per unit of circumference

    Hello all I am trying to find the hydrostatic force of a cylindrical tank of water. I was hoping someone could help point me in the right direction. I have a cylindrical water tank. The dimensions are as follows:- I need to find the magnitude of the hydro static force per unit of...
  18. M

    Hydrostatics Pressure - Finding thrust and resultants

    Homework Statement I'm getting stuck with this one and in need of some direction! Obviously I'm not looking for a direct solution, but maybe a outline of what I should be doing? (I'll attach an image in a few minutes) <Image here incoming!> Known data: d2 = d1 / 2 F = thrust force (N) Pa = ρ...
  19. R

    Impossible hydrostatic scenario

    Homework Statement There is an infnite high hydrostatic head in an infite high tank on the surface of earth. How big is the pressure p(r) in tank at a distance r. Ignore the rotation of the Earth and assume the water stays liquid. ( So basically ignore it's an impossible scenario )...
  20. M

    Why can't we use the hydrostatic pressure gradient to do work?

    Is there any way to harness the hydrostatic pressure gradient to generate energy? The pressure at the surface of an ocean is atmospheric pressure.As we descend down the ocean, the pressure increases .After a point, the pressure will be very high.Why can't we use this pressure difference to do work?
  21. M

    Which equation to use for hydrostatic pressure?

    Homework Statement h = 10 ft RHO = 10 ppg (or pounds/gallon) Homework Equations P = 0.052 * RHO * h P = RHO * G * h I am very confused right now as why each equation gives a different answer! What are the correct units for the 2nd equation and how do I convert from second equation to the...
  22. K

    Hydrostatic pressure distribution despite fluid motion

    Hello, in some exam questions I've looked at it is stated that the pressure distribution is hydrostatic, even though there is fluid motion. (In these cases the velocity has been constant over the section where the pressure is said to be hydrostatic). Is it really possible to assume that the...
  23. C

    What happens to air in a hydrostatic test

    I am a contractor. I install water lines. Once installed we have to pressure test them. We pump the lines up to 150 PSI of water. If the PSI drops one of 2 things is wrong, either i have a leak in the line, or there is a small amount of air in the line. Generally if it is air, it stabilizes...
  24. H

    Force exerted on the horizontal bottom of the container

    Homework Statement In an empty container, having the shape of a Rectangular Parallelepiped, with width l=0.5m and MN=H=0.4m, and NP=L=0.75M. we poureda mass of mercury =2448kg. T0,T1,T2 have the same section which is 0.2 m^2. we give g=10N/kg, and density of mercury u=13.6 g/(cm^3)...
  25. zul8tr

    Hydrostatic force on identical containers filled with equal volumes of water

    In the sketch are 2 identical containers filled with equal volumes of water. Which has a greater absolute vertical force only on the conical wall and by what relative amount? Not a classroom or homework problem.
  26. T

    Hydrostatic equlibrium and Centre of pressure

    Homework Statement A uniform star has a mass of M and radius of R,use the hydrostatic equilibrium equation to find its centre pressure. (note: not the minimum centre pressure) Homework Equations $$\frac{dp}{dr}=-\frac{Gm\left(r\right)\rho \left(r\right)}{r^2}[1]$$ The Attempt at a Solution...
  27. MermaidWonders

    MHB Integral Applications - Hydrostatic Pressure + Force

    Question #1 - A lobster tank in a restaurant is 1 m long by 0.75 m wide by 60 cm deep. Taking the density of water to be 1000 kg/m$^3$, find the water forces (a) on each of the larger sides of the tank; (b) on each of the smaller sides of the tank.
  28. F

    Hydrostatic Pressure and its Effects: A Visual Explanation

    Homework Statement I drew a picture[/B] Homework Equations I drew a picture The Attempt at a Solution I drew a picture
  29. J

    Hydrostatic pressure in a tilted tube

    Homework Statement Prove that the hydrostatic pressure difference between the liquid surface and the base of rightmost tube is ρgh (h is the vertical distance of the liquid surface from the base ) ? Homework EquationsThe Attempt at a Solution I would like to prove this result just out of...
  30. B

    Hydrostatic Pressure: Resultant Thrust & Overturning Moment

    Homework Statement [/B] Hello, am i on the right track with this problem. I am not sure if i have done the it correct. The part i am unsure on is b). Not sure if i have calculated it correct. Part of a sea defence consists of a section of a concrete wall 4 metres high, and 6 metres wide. (See...
  31. Likith D

    Regarding the pressure at a point in a "rested" fluid

    Hey! I just came across this text ; from http://www.feynmanlectures.caltech.edu/II_40.html I tried to find "the law of hydrostatics" on the internet, to find no other mention of it. (would appreciate links to more details on it or any ideas regarding the topic) What is really puzzling is how...
  32. I

    Hydrostatic pressure (infinitesimally small column of water)

    This is a hypothetical question: since hydrostatic pressure is calculated as depth of water times its density, would a column of water less than a square foot in cross section still have a pressure at the bottom of depth*density of water? For example, if I had a 1" thick by 1ft wide by 5' tall...
  33. V

    Hydrostatic equilibirum in slowly rotating star

    Hello, in article Slowly relativistic stars by James B. Hartle (http://adsabs.harvard.edu/full/1967ApJ...150.1005H) is equation of Newtonian hydrostatic equilibrium, eq. (5). $$const.=\int_0^p\frac{dp}{\rho}-1/2(\Omega \times r)^2+\Phi,$$ where ##p## is pressure, ##\rho## is desinty, ##\Omega##...
  34. tom.stoer

    Hydrostatic equilibrium and Navier-Stokes equations

    Is it possible to derive the condition for hydrostatic equilibrium or the Navier-Stokes equation for a self-gravitating fluid - e.g. for water on a planet with non-homogeneous density - based on a variational principle? (the planet itself is assumed to be a fixed hard core not subject to the...
  35. J

    Calculating Filling Time for a Diving Tank with Changing Hydrostatic Pressure

    Hey, Let's imagine I have a tank, filled with air at atmospheric pressure. This tank have a closing/opening valve. I dive this tank at 100m under water and opened ce valve, my filling speed will be sqrt( 2*g*h) with h=100m. Now, if i want to dive the tank (with a volume X) continuously at a...
  36. T

    Question about hydrostatic pressure

    Hi, I have a 12(W)x18(L)x1m concrete tank installed underground and it will be subjected to pressure of 0.5bar. To test the tank for leaks, instead of pressurizing the tank using pumps or air blower, my supplier suggests we use a 1 inch hose with 1 end connected to the top of the tank...
  37. M

    Hydrostatic forces on a hinged gate

    I'm trying to just find the hydrostatic force on the hinge of the gate in the image attached, and while not labeled, the thickness out of the page is ##w=5##. My thoughts are to set up this integral $$\vec{F}_p = \iint \rho g y \hat{n}\, dA = w \rho g \int_0^8 y \left(...
  38. S

    Static pressure and hydrostatic pressure

    Hello can someone explain the difference between static and hydrostatic pressure in terms of a water in a glass
  39. hominnimoh

    I Hydrostatic Pressure and Fermi Surface

    How exactly does hydrostatic pressure affect the shape and size of each Fermi surface in Figure 4B? How do you read this figure or what exactly is it showing?
  40. Jules Winnfield

    I How to extract dark matter mass from a hydrostatic study

    In 2005, A. Vikhlinin et al. made a hydrostatic equilibrium study - https://arxiv.org/abs/astro-ph/0507092 - of some dozen galaxy clusters. These hydrostatic studies are useful because they don't contain the M/L assumptions of other methods. From this document, I'm trying to extract the dark...
  41. O

    Calculating the hydrostatic pressure on a tube

    Hey guys. I'm working on a submarine project and my goal is submerging it to 100m, but I'm having trouble calculating the parameters i need. I'm working with a perspex tube (E is about 1.3Gpa), 26mm inside diameter and 30mm outside diameter. the tube X meters long with inside pressure of 1 atm...
  42. thebrennus

    Determining hydrostatic force on a sphere

    Homework Statement A solid sphere with radius ##R## is submerged on water at a depth ##h_1##. Water's specific weight is ##\gamma##. Determine both horizontal and vertical forces exerted by the water on the surface of the sphere, in terms of ##R## and ##\gamma##. Homework Equations My lecturer...
  43. jdawg

    Hydrostatic Pressure on a Curved Surface

    Homework Statement Gate AB is a quarter-circle 10 ft wide and hinged at B. Find the force F just sufficient to keep the gate from opening. The gate is uniform and weighs 3000 lbf. Figure and solution attached. Homework EquationsThe Attempt at a Solution I've been able to figure out how to...
  44. jdawg

    Deriving hydrostatic pressure equation for an ideal gas

    Assume: Hydrostatic Situation, ideal gas Use empirical formula T = T0 - Bz I have rechecked my work several times and can't seem to find a mistake. The answer is supposed to be: p2 = p1((T0 - Bz)/T0)(g/Bz) dp/dz = -ρg Now substitute ideal gas equation for ρ dp = -(p/RT)g dz ∫(1/p) dp...
  45. jdawg

    Derivation of Hydrostatic Equations Fluids

    Homework Statement I'm having a little trouble understanding how to derive the hydrostatic equations for fluid mechanics! My professor showed the derivation with respect to y in class, and it kind of made sense to me. Now I'm trying to see if I can derive the equation with respect to z and x...