Questions tagged [fluid-statics]

Fluid statics or hydrostatics is the branch of fluid mechanics which deals with the study of fluids at rest and the pressure exerted by it on an immersed object. If your question is about the study of fluids in motion, use the tag "fluid-dynamics" instead.

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How does nitrogen narcosis occur?

I'm confused as to how the partial pressure of nitrogen inhaled from an air tank while scuba diving increases as you descend deeper. Obviously the pressure of the water above you increases the deeper ...
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Find the density of liquid Y

While solving the question, I had some confusion, that we know net pressure at equal depths must be equal in fluids so if we try to equate the pressures at depth of 8cm (instead of the conventional 10 ...
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"Outrunning pressure": Liquid in free-fall

I've checked out related questions and didn't see an answer to my question. Scenario: Liquid in open-top container, together accelerating downward with magnitude $g$. It was straightforward for me to ...
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1 answer
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Oil and gravity

If we both oil in a cup and then we put water in the same cup, the oil will rise to the top. But isn't gravity supposed to stop that. Like if the oil was at the bottom isn't it supposed to stay there ...
2 votes
1 answer
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Does pressure decay exponentially for a mixture of gases?

According to this answer, the partial pressure of a gas decreases exponentially in height, when placed in gravity. For a mixture of gases, the partial pressures of each component follows this law ...
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Finite Element Analysis of flow along a cylinder

Is there a mathematical iteration formula (known as finite element analysis that can investigate the flow perpendicular to the curved surface of cylinder? I am wondering what type of iteration method ...
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Water tower hydro generator? [closed]

$500$ gallons, $100$ feet high, at tank $10$ inch pipe, every $4$ feet a reduction of $2$ inch pipe diameter, ending in $1/4$ inch tubing to jet nozzles, each nozzle would spin an independent ...
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Questions about Bernoulli Equation in moving reference frames paper

I am trying to understand this paper (PDF). I think I follow until equation (6). The authors say that after cancelling terms, you get out the standard Bernoulli equation "which thus only holds ...
3 votes
5 answers
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Pascal's law further simple proof for students of an high school

Pascal's law states that a force applied on a surface of a fluid is transmitted within the fluid in all directions of the fluid with the same intensity on equal surfaces. Similarly, it can be stated ...
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Filling a tank by gravity from a larger, higher tank

First post. Hopefully somebody might be able to help. As per the attached picture, we have a diesel generator day tank which is gravity-fed from a larger, higher storage tank. We also have a vent ...
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Confused about how the formula for buoyancy is derived

The formula for fluid pressure of any point at depth $h$ in a fluid is $p = hρg$. Here, the formula is derived by calculating the mass of the fluid column above the point (which is equal to $Ahρ$, and ...
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What is static fluid-structure interaction?

I have came up across the term "static fluid-structure interaction" and I was thinking about it. Static fluid alone means a fluid that is static, or stationary (not moving). But how is it ...
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1 answer
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Why is the weight ignored in buoyant force derivations?

why is it that the weight that the object makes is totally disregarded in these derivations of the buoyant force? Shouldn't that F up be the weight of the water in the top + the weight of the object? ...
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Why is the water level in the tube tilted instead of horizontal, like the water level in the rest of the cup?

The first photo is the original photo I took, while the second one has a faint red outline of the surface level of the water inside the tube and a faint blue line on the surface level of the cup. The ...
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When the water flows out, will the outlet at the bottom of the beaker also produce a reaction force?

Suppose there is a beaker filled with water, and there is an outlet on its side wall. Under gravity, when water flows out of the beaker outlet, there will be a reaction force at the beaker outlet; If ...
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Why water pressure is higher in the lower stories of a building when one can can open the faucet on the roof story and have the water free fall?

Say a building comprises 7 stories. Imagine also that the upper story has a faucet that leads to the ground (level 0) Now it is well known (alas for those on the upper stories) that water pressure is ...
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1 answer
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Time required for the waves to disappear from the water

Suppose that some liquid was agitated in a container so that the height of its surface, represented by a function $z(x,y,t)$, is known at some instant $t_0$. How to compute how long does it take until ...
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Bernoulli equation and contact angle: Slip or permeable boundary?

It is a simple question related to Bernoulli equations and permeable boundary. Let $u$ be the velocity potential associated to the velocity fluid $V=\nabla u$ and suppose that the fluid is ...
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Stress-energy tensor for ideal gas (not perfect fluid)

If I understand correctly, an ideal gas has viscosity (i.e. shear stress) whereas a perfect fluid does not. So I am right in thinking that the stress-energy tensor for an ideal gas should not be ...
1 vote
1 answer
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Sealed container with water with air bubble at the top — Basic hydrostatic principles fail? What is the pressure distribution?

From hydrostatics, it is said that when you have a liquid with no moving parts, the pressure does not vary on any horizontal slice of the liquid. The pressure only varies with depth. Thinking about ...
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What if there were no surface tension in the upside-down water cup trick?

There is a famous trick that goes as follows. Take a cup/glass that is partially filled with water. Place an index card over the top. Turn the entire thing upside-down (while keeping the index card at ...
2 votes
1 answer
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How is underwater pressure affected by ice?

Let's say I have a bucket of freshwater exposed to an environment where ice can form (less than 0C, normal atmospheric pressure, etc.). The bucket is on the ground so ice will only form on the top and ...
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What is going to happen if you place a pitot tube on a working syphon?

I was trying to understand the pressure difference across 2 points on a working syphon and came across this youtube video: https://youtu.be/ofoR4Sgk1b8. Previously i thought that at any point on a ...
2 votes
3 answers
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How is the time dilation changed on a rotation fluid ellipsoid?

Are the polar and equatorial radiuses of a rotation fluid ellipsoid approximately depended of the rotation velocity by this equation $$\frac{{GM}}{{{r_{{\text{pole}}}}}} - \frac{{GM}}{{{r_{{\text{...
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Is the vertical pressure force on the bottom of a liquid container equal the weight of the fluid above the surface area?

I had an exam question few days ago that asked about the vertical force on the bottom surface of containers shaped like the image attached. All of the containers have the same area on the bottom of ...
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What is physically going on when I stick my finger in a glass of water and the scale tips downards implying it got heavier?

Suppose I have a scale with a glass of water on one side and a counterweight on the other side. If I stick my finger in the glass of water I observe that the water side of the scale becomes heavier ...
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Why is the pressure inside a fluid is equal in all directions? [duplicate]

Actually, I am thinking that the fluid pressure occurs as the result of the forces acting on each molecule from each other. If it is true, then why should the horizontal force be equal to the vertical ...
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How to "calculate" correctly the liquid column height in not "simple" capacities?

As I was told on a youtube lesson, to calculate the hydrostatic pressure on the bottom of a capacity, that's on the picture below, I need to use the h1 height(see that formula on the picture). And it ...
3 votes
2 answers
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Would water flow from the higher container to the lower one? [closed]

Two identical open-topped containers contain identical amounts of water, and they are connected by a tube at their bases. Container A is higher than Container B. How much water, if any, will flow from ...
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How to measure cylinder volume by water weight

I'm trying to determine the volume of a cylinder ( 25 cc approximately) in a precise way. First I'm measure the weight of the empty cylinder. Then, I'm add water to the cylinder until the water ...
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-1 votes
1 answer
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Snorkeling vs diving with a breathing cylinder

If diving with 5m snorkeling pipe our lungs would collapse due to 0.5 atm difference, right? If diving with a cylinder that has air with atmospheric pressure (the pressure our lungs can use), we can ...
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1 answer
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Which forces keep two soap bubbles together?

I am trying to calculate how many soap bubbles can hang together against the force of gravity, but I am not sure what forces hold them together. My guess is the surface tension, so an equation like $F=...
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1 answer
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Pumping out an absolute pressure

I'm just going over some basics and I have come to a little misunderstanding I have. The question is about pumping out an absolute pressure from a sphere split into two hemispheres and the amount ...
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What is the cause of the pressure of water at the point $C$ or $D$? [duplicate]

We have $P=\rho gh$ where $h$ is calculated from the free surface, Hence $P_A=P_B=P_C=P_D$. But at the point $A$ we say the pressure is from the fluid column above this point. I'm wondering what is ...
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Buoyancy and stability

I don't understand how does a rotating moment caused by the weight force form when a submerged object is tilted like this. I understand that the buoyancy force produce a moment about CG because of the ...
1 vote
1 answer
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Pascal's law question

I apologise for the very basic question, I’m just trying to grasp the concept of Pascal's law. I’m familiar with the fact that if pressure is applied to a confined liquid, the latter will be applied ...
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How can I determine the total energy and power provided by an ocean wave when it reaches shore?

When an ocean wave travels to the shoreline and breaks, how much energy is released? I did some research on finding out a formula to calculate how much energy is stored and then released by ocean ...
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Fid the coefficient of thermal expansion of liquid

Please explain why we get two different expansion for two different methods i.e. when we equate the pressure at Aand D ,and at C and B and which is correct and why because in book and at other ...
1 vote
1 answer
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A question on Hydraulics from a 19th century book

The following passage is from a 19th century physics text. "Take a strong glass tube about three feet in length, and tie over one end a piece of well-soaked bladder. "When thoroughly dry, ...
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2 answers
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Is the pressure-gradient force that causes hydrostatic equilibrium entropic, contact, or both?

This question considers classical fluid mechanics, particularly the kinetic theory of gasses. In the simple one-dimensional gravitational setting, a fluid is in hydrostatic equilibrium if $\frac{dP}{...
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In Hydrostatics for a plate submerged in a fluid, what is the product of inertia of the plate, computed in the plane of the plate?

I'm reading on the position of center of pressure of a plate submerged in a fluid. In relation to this, the author writes: "I_xx is the area moment of inertia of the plate area about its ...
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Collecting gas over water -- is the textbook explanation wrong?

I was revising my chemistry and while doing a problem on collecting a gas over water, I felt like I disagreed with a part of their explanation. Firstly, an illustration to show how I think about ...
2 votes
1 answer
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Resulting height of displaced fluid after adding a floating object

I've had contradictory experimental results from my calculations of displaced fluid height after adding a floating object. Consider the following scenario: Using a test tube of diameter $D=1.70$ cm ...
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1 answer
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DISPLACEMENT OF WATER [duplicate]

Floating objects displace their weight? what does this statement actually mean? Does this mean that floating objects displace the amount of water that's equal to their weight and so buoyancy is equal ...
2 votes
1 answer
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Displacement of water - Archimedes' principle

Floating objects displace their weight and objects that are completely submerged in water displace their volume. So, my question is that does a floating object displace less water than an immersed ...
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In a centrifugal separator how does the heavy or light phase move upwards?

I've been studying about the working principles of a centrifugal separator. Even though i understand how centrifugal force separates the liquid into 2 phases(heavy and light) i cant make sense of how ...
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2 answers
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What is $V$ in Buoyant force $V\rho g$? [closed]

As, Buoyant force is the net upward force on any object in any fluid. If the buoyant force is greater than the object's weight, the object will rise to the surface and float. If the buoyant force is ...
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Am I understanding Pascal's law the right way?

I'm just intuitively trying to figure this out, so I would like for someone to see, if I'm understanding pressure transfer right. In a solid an external force acting upon it gets equally transferred ...
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Atmospheric pressure on a barometer

In the above image $P_{a}$ shows the atmospheric pressure. As a consequence of $P_{a}$ the fluid moves upwards in the testube(Which is shown in the red arrow above). Suppose that the fluid is water ...
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4 answers
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What is the microsopic reason why hot air rise? [duplicate]

The common explanation for why hot air rises is a macroscopic one. That is that the hot air is higher pressure, lower density, and therefore gravity affects it differently than the surrounding cold ...

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