# 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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1answer
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### Pressure after cooling of the closed vessel

I have stuck with the engineering calculation for my work Suppose that we have a underground pipeline with constant flow of liquid, which connected with closed underground vessel through the valve (...
1answer
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### Why is force due to surface tension neglected here?

I was solving question 2.07 from MIT's advanced FM and it was asked to find the force required to hold to glass plates in place when water is placed between them. I solved by showing that due to the ...
1answer
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### If atmospheric pressure causes an increase in a fluids pressure, wouldn't attaching a piezometer to a pipe cause the change in fluid pressure inside?

So say I've got a pipe, and it's got some kind of an internal pressure. Now, it's completely enclosed, so atmospheric pressure cannot affect it. Then, if I wanted to measure the pipe's pressure by ...
1answer
74 views

### How does a diving bell NOT get flooded with water, and does it work with other liquids?

If the air in an upside-down container (such as a diving bell) weighs much less than water, then why does it not get compressed down until it is the same mass per volume, when submerged even to a ...
2answers
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### What is the center of buoyancy for objects submerged in two liquids?

Suppose a solid object is submerged into two immiscible liquids stacked one above the other in such a way that some part of solid is in air some in 1 liquid and some in another liquid. Can we say the ...
6answers
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### Why should water fall down from an upside down glass of water?

Suppose I have an upside down glass of water that I somehow brought in the configuration shown below (without any air between the glass and water). Now the water will obviously fall down but my ...
0answers
22 views

### Regarding the case of pressure of a fluid in a closed moving container [closed]

i found that pressure is supposed to be a isotropic quantity,and using this information i found that pressure at a point in a moving container that is open at the top will be equal due to both gravity ...
1answer
34 views

### How do you determine the volume of a balloon so that it takes off? [closed]

Could someone explain me the solution please? I am stuck in this exercise. Question: A balloon has the mass m = 10 g and is inflated with helium so that the final pressure is p = 1.5 bar. How large ...
4answers
118 views

### How do you visualize the particles in liquid at a molecular level?

I am studying about fluids at the moment and I never been so massively confused since about some fluid related topics that I thought I was confident about like liquid pressure, velocity of particles, ...
0answers
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### Forces due to surface tension

In the above diagram I m not able to figure out why fsa acts as a force due to surface tension and why is it different from fls? Is it because adhesive forces depend on medium? Can someone explain how ...
6answers
6k views

### Why do rotten eggs float in water?

My mom told me that one can check whether an egg is rotten by sinking it in a glass of water. If it floats, then it is rotten. I didn't find any explanation for this phenomenon. If anyone knows one, ...
0answers
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### Blood flow problem using the continuity equation

Blood flow increases during exercise by the dilation of blood vessel diameter together with an increase in blood pressure. Suppose that the flow rate increases by a factor of 4.5 and blood pressure ...
4answers
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### Room Pressure and Tiny Gaps

First of all, how can atmospheric pressure be same in a closed room when it clearly depend on the height of the air column. Compared to atmosphere, the room few metres high so how can air pressure be ...
0answers
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### Surface tension (capillary action)

Why we assume that meniscus that is formed when a capillary tube is immersed in a liquid is spherical (neglecting mass of the meniscus)? What will be the shape of the meniscus when mass is not ...
2answers
29 views

### Why is pressure $\rho g R$ at all points on the base of this upside-down container

The container is inverted and filled with water through a hole on top and it is said the pressure on the bottom of the container is $\rho g R$ which I agree with for only the point directly bellow ...
2answers
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### How do particles in liquid move at the microscopic level?

I have just begun learning the topic of fluids in physics. I am trying to understand the concept of fluid pressure and its relation to fluid flow, velocity, buoyancy but in my attempt to understand ...
2answers
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### What do you really mean by fluid pressure?

I feel like the more deeply I am studying about fluids in physics, the more I realize that I don't really understand the basic concept of fluid pressure. Like firstly what is meant by fluid pressure? ...
3answers
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### How high would a half deflated ballon float outside of a third floor?

this a question that has been haunting me for many years now. If I have a half deflated helium baloon that floats one meter above the ground on a third floor and I take it outside, will it float one ...
1answer
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### Water pressure at the base of two different sized cylinders [duplicate]

Will the water pressures at the base of two different sized cylinders be the same if they are filled to the same height? Sorry for crappy drawing
1answer
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### Simple shear force calculation for the flat face of a container of fluid

I'm trying to model a situation I'm working with, to estimate roughly the forces that I have to resist. But my physics is rusty and I'm not 100% sure how to get it right. The model shows a side view ...
1answer
64 views

### Regarding buoyant force acting on a cone in an accelerated container [closed]

While solving questions related to fluid mechanics, I came across this particular question: The correct options are (A), (B) and (C). I was only able to mark option (A) with certainty. I have some ...
2answers
55 views

### Flattening of large liquid drops

I have read that liquid drops are spherical in shape due to the surface tension of the liquid which tend to minimise the $\frac{surface}{volume}$ ratio of a given volume of a liquid. But in real life, ...
1answer
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### What can cause different levels in communicating vessels?

I have three small tanks connected by a 6 mm pipe. The pipe fits into an hole made at the bottom side of the tank. Pipes are connected at the junction point using a T-shape connector. Here a drawing ...
1answer
60 views

### Who does all the calculation in Archimedes Principle? [closed]

Let's do an experiment. In the first half of the experiment, you ask some geometers to determine the volume of a pineapple. They would model the 3D shape of the pineapple, which is a pretty tricky ...
4answers
106 views

### Does buoyancy exert the same or different upward force on two dissimilarly shaped, but same volume objects?

Suppose I have two objects of exactly the same volume, one is a sphere and one is a cube. If the objects are completely submerged in water, is the upward buoyancy force the same or different on these ...
1answer
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### How can air pressure be equal in all directions?

Lay on the ground in a bright sunny day of spring and look the sky. Feel the air pressure on you. Now lay on your stomach and your back exposed to sky. You won't feel any change in air pressure. You ...
3answers
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### Does a floating ship increase the pressure on a scuba diver?

In the article Ship Traffic Increases Dramatically, to Oceans' Detriment , there is a quote (emphasis mine) : "I was surprised to see that in 20 years, the growth is almost fourfold, or almost ...
0answers
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### English translation of Oseen's book on Hydrodynamics

Is there an English translation of Oseen's 'Neure methoden und ergebnisse in der Hydrodynamik' available anywhere? I could not find it on Amazon. Google search didn't shed any light. I believe that ...
0answers
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### Contact angle in a capillary tube

I know that contact angle is a result of adhesive and cohesive forces but I am not able to draw a diagram of forces on the liquid in a capillary tube (in terms of adhesive and cohesive forces). In ...
1answer
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### If a free jet of liquid is exiting from a tube into the air, why is the pressure of the liquid exiting atmospheric when not submerged?

There have been a few questions already asked that are similar to what I am asking. Why is the pressure of a jet, as it exits, is always the ambient pressure? [closed] If a hole is drilled at the ...
2answers
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### Is the buoyant force of air implicitly neglected for an object half-inmersed in water?

I saw in this answer that the atmospheric pressure is conveniently canceled mathematically when taking the atmospheric pressure at the level of the top of the object. However, when I was inventing ...
2answers
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### What's the pressure inside a barometer?

I have the following problem I'm trying to solve. Let's say we have a barometer filled with water as in the following diagram: The question to be answered is what's the pressure $p$ on the inside of ...
2answers
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### When putting a floating object in water, why the displacement of mass of water is not equal to only the part of the object inside the water?

In this question Will a bathtub full of water weigh more if I add something that floats in the water? the marked answers mentioned a special case where the bathtub is full to a brim and the boat is ...
2answers
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### How much vacuum is needed to lift?

Just like a balloon of Helium lifts about 1.02g for being less dense than the air. Does the same principle applies to vacuum being less dense than air? And if so, how much can a ballon (1L) of vacuum ...
4answers
59 views

### How can an object float on the surface of a fluid?

According to Archimedes Principle, We know that buoyant force on object ${F_{buoy}}$ is given by, $F_{buoy} = V_{immersed} * {\rho}_{fluid} * g$ where, $V_{immersed}$ is the volume of object that ...
1answer
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### Pressure change caused by rotation contradiction (Rotating fluid in a bucket)

I am reading through this article which analyzes the pressure in the liquid rotating in a cylindrical container, in it there are two expressions derived for height of the liquid which seem to be ...
4answers
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### Can a body float in the middle of a fluid?

Let's say we have a cubic body of side $a$ and made of a material with density $\rho$ and we measure its immersed height in a fluid of density $\rho_f$ by the variable $y$. Then, its potential energy (...
2answers
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### Pressure of water derived from weight vs pressure of water derived from Pascal's law

Assume that I fill a floor measuring $2 m^2$ in a room with $1 m$ of water, and the rest of the room is full of air. I have used two ways of finding the pressure of the water on the floor: First, ...
1answer
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### The Force on a Dam not accounting for atmospheric pressure?

I have seen this problem in one textbook (Physics for Scientists and Engineers, Raymond A. Serway, 2018) and in several places on The Internet, where we have a dam and we need to calculate the total ...
3answers
80 views

### What the air pressure inside an air bubble in water [closed]

I am a newbie in physics and have a homework problem, I hope I am not asking something stupid, since I don't learn physics nor am I going to do anything advanced with it. So let's say we have a bubble ...
1answer
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### Will fuild in the red circuit mix in the blue circuit

I have a conceptual question regarding hydraulic circuits. I have two circuits A(blue) and B(red), connected by a 3 way valve. The following are description about the circuit A and B, containing ...
1answer
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### Is there such thing as a non-turbulent wake?

We learnt in our fluids course that boundary layer separation can occur even for laminar non-turbulent flow (for high viscosity fluid). In this case, shown as ‘steady separation’ in the diagram below. ...
1answer
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### Do all Joukowski aerofoils violate no-penetration condition at trailing edge?

In our fluids course we calculated the velocity distribution around a completely symmetric Joukowski aerofoil (as shown below) and used the Kutta condition to ensure that the velocity was not infinite ...
1answer
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### What is the change if a droplet of water is added to another droplet of water on a flat surface

There is a tiny droplet of water lying on a flat clean surface and I add a droplet of water to the tiny droplet on the surface. How can I explain the change that might occur?
1answer
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### Pascal's law and pressure in fluid at a depth

We were introduced fluid mechanics in class today I am thoroughly confused on some basic points- What is the proof of Pascal's law? And what does it exactly mean? I know that it states that the ...
1answer
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### Does a non-uniformly-dense pyramid floating in water displace more water/“float lower” than a uniformly dense one?

Consider two square, equilateral pyramids of equal volume $V_{object}$ and equal mass. One pyramid is uniformly dense The other pyramid has most of its mass concentrated at the apex. Both pyramids ...
4answers
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### Static pressure on the bottom of cylinder [closed]

i have a little doubt about a very simple problem regarding static pressure on the bottom of two different cylinder. We have the same quantity of liquid inside two cylinder with different section, as ...
1answer
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### Force caused by pressure

I would like to get one thing straight in my mind: If I fill a balloon let's say with 10 bar of air. Is there a formula that relates the force acting on a point $F(x)$ where $x$ is a point on the ...
2answers
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### In a mixture of two immiscible liquids, why does the denser liquid always settle down?

The same is not true for solids, e.g. an iron block kept over a wooden block.
3answers
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### How is buoyant force still upwards in a mixture of fluids

For objects 1 and 2, how is the buoyant force by oil still upwards? Shouldn't the pressure caused due to the oil push it down?