Hydrostatic Definition and 242 Threads

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. 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...
  2. F

    Floating, hydrostatic forces, average density

    Hello Forum, I am revisiting Archimedes principle and its important consequences. I am aware that a cube (homogeneous) made of iron will always sink in water regardless of its mass. If we changed the iron cube into a different shape (cone, cylinder, prism, parallelepiped, etc.), the object...
  3. D

    Density of star from hydrostatic equilibrium and pressure

    Homework Statement Assume that the pressure p in a star with spherical symmetry is related to the density \rho by the (distinctly unrealistic) equation of state p= \tfrac12 k\rho^2, where k is a constant. Use the fluid equilibrium equation obtained in Problem 23 to find a relation between \rho...
  4. Virang807

    I Question about Hydrostatic Force?

    Hello! I am currently in Calculus 2 and we are dealing with hydrostatic force. I get the integration that happens but I always seem to have trouble with solving the word problems. With this problem, I realize that I use integrate by making an infinite number of rectangles on the 2 triangles. I...
  5. Virang807

    How Do You Calculate Width in Hydrostatic Force Problems with Varying Depths?

    Hello! I am currently in Calculus 2 and we are dealing with hydrostatic force. I get the integration that happens but I always seem to have trouble with solving the word problems. With this problem, I realize that I use integrate by making an infinite number of rectangles on the 2 triangles. I...
  6. Andreas C

    I Sun and hydrostatic equilibrium

    I've been trying to make an estimate for the pressure of the sun's photosphere using some sort of hydrostatic equilibrium equation, but I can't seem to get one that even comes close to agreeing with observations. Does anyone know what the right formula is and what the right way to approach the...
  7. jzwillows

    Hydrostatic force on the bottom of a container

    Is the force from a liquid against the horizontal bottom of a container a function of depth and cross sectional area at the bottom only, i.e., computed by the formula Force=unit weight of water x depth x cross sectional area? If so the force could be greater than the weight of water and that...
  8. Ravi Singh choudhary

    Pressure is equal or force is equal at the bottom?

    Problem Statement: Both containers are just equal in volume and having same height; you can assume one is upside down of another. What is pressure at the bottom of the containers. Let's say left side is container 1 and one on right side is 2. Relevant equation: h is the depth of fluid from the...
  9. Ravi Singh choudhary

    Hydrostatic stress on cube placed in deep sea

    Ques: If one metal cube placed in deep sea where will be maximum shear stress in cube? What I know: In hydrostatic condition there would be no shear stress, that means on any face of cube there would be not shear stress at all. In case of two dimensional stress; if we have same...
  10. sunes123

    Pressure & Hydrostatic Pressure

    Hello, I would like somebody to help me with few simple questions for my homework. I did try to solve them but I failed at few of them. Here are the two papers I need to help with. I need help with the highlighted excerises. I tried some basic formulas for pressure and hyrdostatic pressure but...
  11. MrGianmarcoD

    I Hydrost Pressure Integration Problem (Environmental Physics)

    Hey guys! I'm working on a problem for which i somehow just can't figure out what I'm doing wrong. This is the problem: I think I've figured it out, but somehow i think i make an error with the maths. First of let's determine the equation for the temperature (in Kelvin): $$T(z) =...
  12. B

    Cylindrical barrel Hydrostatic Pressure

    Homework Statement A circular cylindrical barrel is half full with oil. If the diameter of the base is 8.0 m, find the net force against each end if ρo = 800 kg/m3. The cylinder is on its side. Homework Equations F=P*A P=ρgdy The Attempt at a Solution P = ρo*g*h, where h is the radius which...
  13. M

    Hydrostatic Pressure Curved Surface

    Hi PF! I have been reading and reading for a clean explanation for the hydrostatic force of a curved submerged 2-D (or 3-D if you're up to it) surface. I really don't care what the curve looks like: quadratic, circular, partway sinusoidal, etc. All articles I read involve the centroid, but...
  14. A

    Hydrostatic forces on a submerged curved surface question

    Hi, i would like to know how to do this question for fluid mechanics. Sorry as I am new i didnt know how to upload images so i just uploaded the image in justpaste, here is the link http://justpaste.it/pz7r
  15. M

    Basics of hydrostatic force on a plane surface

    1. Introduction Pressure of a fluid exerts thrust on each part of a surface with which the fluid made contact. Each forces distributed over the area have a resultant magnitude and direction that is very crucial. For a horizontal surface, the pressure does not vary over the plane. Thus, the...
  16. L

    Fluid Dynamics - Hydrostatic Pressure #2

    Homework Statement a Flat rectangular door in a mine is submerged from one side in water. The door dimensions are 2m high, 1m wide and the water level is 1.5m higher than the top of the door. The door has two hinges on the vertical edge, 160mm from each corner and a sliding bolt on the other...
  17. L

    Fluid Dynamics - Hydrostatic Pressure

    Homework Statement A rectangular vertical plate is submerged in water. The top edge is horizontal and at a depth of 0.6m. The length of the vertical edge is 1.2m. determine at what dept under the water surface a horizontal line can be drawn on the plate such that the hydrostatic forces on...
  18. R

    Uniaxial compression strength versus hydrostatic / triaxial

    For typical metals used in construction I've seen the compression strength being used in various calculations. Typically I assume this is the uniaxial compressive strength. i.e. Say in a UTM with the specimen laterally loaded. Are there engineering situations where the hydrostatic compressive...
  19. T

    Why Is My Calculation of Vertical Hydrostatic Force Incorrect?

    MODERATOR'S NOTE: THIS THREAD HAS BEEN MOVED FROM ANOTHER FORUM, SO THERE IS NO TEMPLATE. This is the problem here. I am having trouble making progress on this problem after getting the wrong answer for the vertical hydrostatic force. The equations I am using are: fx=...
  20. icystrike

    Therefore, a = 3 and b = 5.Hydrostatic Force Homework: Find a & b

    Homework Statement An object made entirely from one material has a volume of 30m3. It floats in a liquid of density of 3g/cm3 with only half its mass below the liquid's surface. The object is then placed in another liquid of same volume but with a density of 1g/cm3 If the final upthrust that...
  21. Rectifier

    Hydrostatic pressure - barrel vs. small cylinder of water

    This problem was translated from Swedish, sorry for any grammatical errors present. The problem The grey is liquid is water. The small container is a pipe made of glas and the big container is a barrel. Water is poured into the glas pipe. When water reaches 12m over the barrel top(lid) the...
  22. K

    Hydrostatic pressure and Gravitational Potential Energy

    So say I had a glass of water on a table ,with the glass filled to the top. The bottom of the glass, the water would have a higher pressure than the top of the glass. This is the concept of hydrostatic pressure etc. But how does GPE fit into all of this? Does the water at the top of the glass...
  23. Thom_Silva

    Hydrostatic and atmospheric pressure

    So I've been wondering, 10.3 meter of water amount for one atmosphere, and according to Pascal's law pressure can compute by P=P0+ ρgh. If we have a glass with 10 cm of water inside , the pressure in the glass would be lower than atmospheric pressure and therefore when you turn the cup upside...
  24. P

    Units for pressure in a cylinder

    I am calculating pressure on a spherical cylinder of 10 mm diameter by wind tunnel. when measuring values in manometer filled with water which density is 1000 kg/m^3 so by hydro-static formula the pressure difference is [P2-P1=ρg(h2-h1)] so by this formula the ρ unit is in kg/m3 and gravity(g)...
  25. Jason Onwenu

    How High Did Water Rise in the Squalus Diving Bell?

    Homework Statement During a test dive in 1939, prior to being accepted by the U.S. Navy, the submarine Squalus sank at a point where the depth of water was 73.0 m. The temperature at the surface was 27.0 ∘C and at the bottom it was 7.0 ∘C. The density of seawater is 1030 kg/m3. A diving bell...
  26. P

    Understanding notation for hydrostatic equation

    I understand everything (in a really simple way) that lies behind the hydrostatic equation, but I have no idea what this notation (light blue) means. I would really appreciate as much information as possible on this. I want to fully understand it.
  27. O

    Calculating Hydrostatic Force on a Trapezoidal Shape

    It is posted here http://math.stackexchange.com/questions/1290380/how-to-integrate-hydrostatic-force-on-a-two-dimensional-shape and I would really appreciate some insight on this question. I sliced the sections horizontally and could not get the answer.. thank you!
  28. lvluffinz

    Need help obtaining hydrostatic forces on a gate

    I know we need to use F = pgA(h bar), as that's what I'm given in notes and whatnot, but I can't for the life of me get this simple one done. Any help would be GREATLY appreciated as I have an exam coming up on this.
  29. U

    MHB Help with hydrostatic force questions

    Here are the questions... A rectangular swimming pool is 4 feet deep, 75 feet long, and 25 feet wide. It is completely filled with water. a. What is the hydrostatic force on the bottom of the pool? b. What is the hydrostatic force on the shorter wall of the pool? c. What is the hydrostatic...
  30. J

    Expressing the equation of hydrostatic equilibrium

    Homework Statement This problem has been stumping me for days now, I'm sure I'm missing something simple as it's only worth a small number of marks on the coursework. Any help would be appreciated. I've been asked to re-express the equation of hydrostatic equilibrium: dP/dr = - Gm/4πr4...
  31. L

    Fluid statics- pressure intensity and hydrostatic force

    Homework Statement a concrete dam, 20m in height, has a vertical upstream face. if the water level is coincident with the top of the dame, calculate and plot the pressure intensity at 4m intervals over a vertical and thus determine the total hydrostatic force acting per unit width. Show that...
  32. gracy

    Hydrostatic pressure of glomerular capsule

    Effective filtration pressure is produced by 1-blood pressure in blood capillaries which is about 55mmHg. 2-The osmotic pressure of blood which is 30 mm Hg 3-hydrostatic pressure of glomerular capsule which is 10 mm Hg blood pressure in blood capillaries and the osmotic pressure of blood I...
  33. Feodalherren

    Fluid Mechanics: Hydrostatic Pressure on a gate with hinges

    Homework Statement Homework Equations Fluid Mechanics The Attempt at a Solution Lets start with the easy part: The pressure of the air is constant so the pressure will act as if it's a concentrated force on the center of gravity of the gate. F = PA = (10,000Pa)(.3)(.6)=1800N The moment...
  34. 2

    Hydrostatics: What remains the same in a fluid?

    I am looking into hydrostatics, but am now very confused about what has to remain constant in an incompressible fluid. I initially thought that pressure has to be the same all throughout the fluid, and that this is the reason why you can use water or oil when raising a car- you apply a small...
  35. T

    Question about hydrostatic pressures

    Ok so I'm an engineer and I ran into a physics problem the other day and I'm not quite sure how to go about it. I am very farmiliar with hyrdostatic pressures, but in this particular case I'm not exactly sure how the laws apply. I have attached a sketch of my problem. There is an 18-3/4" ID...
  36. E

    Does the flow rate and pressure decrease as the exit height of a pump increases?

    OK, So I have been having an on and off debate with my family about this. I saw a pump at Home Depot that said it has a 30 ft head. Then it went on to show that the flow rate varied as the output of the pump changed in height. Now I thought that this was wrong. I just finished a course in...
  37. L

    Finding the total hydrostatic force that can be withstood

    Homework Statement [/B] We are given a cubic tank, with a parabolic object y = x^2 (one end is -1, 1 and the other is 1, 1 --> it only goes up to 1). The total pressure it can withstand is 160 lbs. Also, the fluid density is 50 lbs. Find: a) Total pressure if water is 2-feet deep. b) Max...
  38. Soumalya

    Hydrostatic pressure distribution for an ideal gas

    Considering a unit mass of an ideal gas in a cylindrical container of volume 'V' at temperature 'T' the pressure exerted by the gas at the walls of the container is given by the ideal gas equation as, pV=RT where 'R' is the characteristic gas constant for the particular gas. Under equilibrium...
  39. T

    Hydrostatic Pressure on Curved Circular Surface

    Homework Statement Picture:[/B] The Attempt at a Solution [/B] Can someone please help..There's no answers and I think my answer is very wrong, as you can see I have pretty much no idea what I'm doing. Thanks Edit: Where it says net force I meant to say net force per unit width. Edit2...
  40. D

    Finding the Ratio of Dimensions for Equal Hydrostatic Force on a Vertical Plate

    1. A vertical plate consists of rectangular and semicircular portion and has dimensions as shown. It is submerged in a liquid such that the upper edge coincides with the free surface of the liquid. What is the ratio of L/R such that force on the rectangular portion is the same as that on the...
  41. U

    Hydrostatic force on submerged rectangle

    Homework Statement (Referring to attached diagram) Find the hydrostatic force F2 on the rectangular part and the point of action of this force on rectangular area. The triangular part is submerged in oil of specific gravity 0.8, while the rectangular part is submerged in water. The whole...
  42. F

    Potential Energy Stored in Hydrostatic Test Unit

    I have a pressure vessel of volume V= 1 m^3 . The atmospheric pressure Patm = 101 kPa and Tatm = 22 C. I slowly pump liquid water into the pressure vessel until the internal pressure reaches P1 = 15 MPa. Also, the process is isothermal because the water was pumped in slowly and heat is exchange...
  43. K

    Calculating hydrostatic force & locating centre of pressure

    Homework Statement A circular viewing window of diameter D = 0.4m is placed in the Holding tank. The top of the window is H = 1.2m below the water surface. Find the hydrostatic force acting on the window and locate the corresponding centre of pressure (CP). There is a diagram attached to the...
  44. B

    Hydrostatic pressure and consequences of pascal's law

    I've had a doubt about the following (somewhat contradictory) statements. 1) pressure applied to an incompressible fluid is equally transmitted at all points. 2) pressure at points at different heights in a fluid placed in a container in a gravitational field are different. Gravity applies a...
  45. A

    Hydrostatic Fluid- Linearly Accelerating Slope

    Homework Statement An open rectangular tank contains water up to about half of its depth. This tank accelerates at a=2.20 m/s^{2} up a slope α (alpha), which causes the free water surface to form an angle θ (theta) with the original horizontal plane. What is the α angle of the slope?Homework...
  46. L

    Hydrostatic Equilibrium in a Star

    Homework Statement Hello. In my homework I was given to find a mistake in a derivation of hydrostatic equilibrium of a star. In contrast to "regular" derivation, where a cylindrical segment is chosen, in HW a segment of sphere is used: Homework Equations Derivation is given as following: a...
  47. W

    Linearly accelerating hydrostatic fluid

    Homework Statement A cart is acclerating to the right with a=3m/s^2. Fluid is in hydrostatic state. Find the force on the back wall. Cart goes .8m into the page. In the image dotted line is free surface when cart is stationary. Homework Equations \vec{\nabla P}=\rho (\vec{g} -...
  48. W

    Basic Hydrostatic Equation for manometers

    The basic hydrostatic equation can be simplified for manometers as follows P_B - P_A= - \rho*g(z_B-z_A) I am having trouble figuring out what the order in which I should put the values of the pressure and elevations. Which is the higher elevation and which is the higher pressure? The order...
  49. J

    How Does Centroid Affect Hydrostatic Pressure Calculation?

    Homework Statement Can you please help me I think I have confused something.We did this in class. A triangular plate with base = 10 m and height 12 m is placed under water with the base at the top at a depth of 8 meters under water and the apex 20 meters under water. Find the hydrostatic...
  50. R

    Hydrostatic pressure and the reading on a scale

    http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/weighing-buoyancy/So I was wondering if both the scales would show the same weight value? (the scales are marked black in the picture) The object on the left is a pyramid and the object on the right is a cube. They are both...
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