# 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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### Relationship between density and temperature - How to know the precise temperature at which a bell inside a Galileo Thermometer will sink?

A Galileo Thermometer consists of bells placed inside a tube that's filled with liquid. As the temperature increases, the fluid density decreases. This leads to a decrease in the buoyant force, and ...
1 vote
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### What would happen to a soap bubble if there were no surface tension?

Suppose you have a soap bubble. Now, suppose that the surface tension in the liquid film that surrounds the bubble disappears instantly. What would happen to the bubble? Also, is it possible to form a ...
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### Why does a bubble created in the body of a liquid pop when it rises to the surface?

Suppose you have a glass of water and you blow bubbles in the water using a straw. The bubbles pop when they rise to the surface of water. Why does this happen? Does the surface tension of water play ...
21 views

### In the real world, how would pipe length/diameter affect hydrostatic pressure? [closed]

I'm currently testing a pressure gauge (in. H2O) using a 1-1/2" PVC (~1' long) connected to a 1/4" rubber hose (100' long) which is connected to the gauge mentioned. Essentially, one end of ...
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### What exactly are cohesive and adhesive forces?

Are cohesive and adhesive forces defined only when at least one of the interacting materials is a fluid?
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### Displacement of the center of mass of water in a slanted container [closed]

I have a cylindrical fluid storage tank, radius $R$, height of fluid $h$, mass density $\gamma$ titled by a (small) angle $\phi$. I need to find the shift of the center of mass with respect to the ...
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1 vote
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### Wrinkling on a fluid foundation [closed]

I have this problem in fluid mechanics/elasticity and honestly don't know how to start. A large elastic sheet of bending modulus A overlies a fluid of density $\rho$. Due to external compression, the ...
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### What is the pressure near the end of the siphon tube inside water?

Consider a standard siphon Tube as shown What is the pressure at point O in the figure? A continuous streamline is there from A to O to B to C to D (correct me if I m wrong) Applying Bernoulli’s and ...
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### The reasoning behind the buoyancy force equation [duplicate]

If I drop a block in water, the pressure experienced on the top of the block is the $\rho gh$. That is because a certain amount of water is distributing a force above the block. I don't understand why ...
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### Hydrostatic pressure on the side wall

I understand well that pressure from the liquid acts perpendicularly on the walls of a cylindrical container. This applies to liquids and gases. I am trying to re-understand sth from the university ...
1 vote
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### Does a falling column of fluid exert the same pressure as a static column?

Suppose you have a $5\,\text{m}$ high waterfall. The water will be accelerated downwards by gravity and impart a force, proportional to the cross sectional area of the falling column of water, on the ...
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### Force and massa unit [closed]

why in this question did the question answer only perform the product between area*P to calculate the mass? Question: Answer: Shouldn't the mass be calculated as $m = (P \times A)/g$? Considering ...
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### Measurement of pressure using pitot tube

We know that pitot tubes are used in measuring velocity of a fluid or dynamic pressure. Now,in stagnation point which is basically the entrance of the pitot tube,the fluid particles are brought to ...
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### Generated pressure when two water interfaces collide

Background I'm studying a bulk cavitaion problem as described in V. J. Cushing - On the theory of bulk cavitation. In the problem an incident shock wave (from the water $z < 0$) is reflected as a ...
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1 vote
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### Pressure measurement using piezometer

When calculating pressure of a flowing liquid,we know that peizometers are used whose one end is open to the atmosphere and the other end is connected to the fluid via a small hole at which we want to ...
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1 vote
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### Doubt regarding the fact that pressure in a fluid at same horizontal level is same

In the diagram shown, we have taken 2 containers of different heights h and h' where h>h'. These containers are immersed in a bucket filled with the a fluid, say water represented with red color, ...
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### Why doesn't the liquid in a liquid-in-glass thermometer slide down when you turn it upside-down?

This question applies to both mercury and alcohol thermometers. I assume the answers would be similar, but maybe not. My understanding is that the capillary in a liquid-in-glass thermometer consists ...
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### How is hydrostatic pressure over a column affected when a barrier is introduced some way down the column?

How is measured hydrostatic pressure of a column of fluid affected by introduction of a barrier at some point within the column. Per attached diagram you have a 100ft column of fluid with gradient of ...
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### In which case do the center of buoyancy center of gravity coincide for a body with uniform density. Would it be completely submerged or just immersed

I read other as well in this topic but they dont exactly explain about the body being partially immersed or completely submerged. I mean does the coincidence of centre of buoyancy and centre of ...
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### Water level in pipe higher than surrounding body of water

I had a question about water pressures and level. We've recently drilled a near vertical hole underground 130m deep by 400mm in Dia into flooded lower underground workings as part of a de-watering ...
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### Buoyant force application [closed]

An open bottle lies on a precise weighing scale. A fly then enters the bottle and flutters around in futile attempt to escape. Another fly, instead of using its wings to fly, uses a small helium ...
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### Pressure at tail end of a water pipe

I was wondering about what is the pressure at end B based on these requirements: the flow velocity through the pipe is vcon(m/s) and flow rate is q(m^3/s), no requirement for delivery pressure at B, ...
242 views

### Bottle with a hole, with straw through the lid

Consider a bottle filled with water, with an air tight lid, with a hole at height h. It's well known that the water doesn't flow out when the lid is closed. Now, if a straw is inserted through the lid,...
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### How to calculate tidal bulge on a shallow, enclosed body of water?

The moon causes a tidal bulge because there is a differential in the gravitational field on the near vs far side of the Earth and the ocean is fluid and can distort to seek the new equilibrium state ...
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### U-tube containing two liquids and accelerating in a horizontal direction

Say I have a U-tube of constant cross-sectional area $A_C$ whose arms are at a distance $L$ apart from each other. The tube contains two different liquids $A$ and $B$ that don't mix, and at first the ...
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### Does having a liquid (less dense than ice) above a floating (in water) ice cube, change the fact that the water level remains constant when ice melts?

An ice cube floats in water, with a liquid (less dense than ice) above it. When the ice cube melts will the water level go up, down or remain constant?
1 vote
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### Can you use formula for viscosity derived from Stokes' law to calculate viscosity of non-Newtonian fluid if constant force is applied?

I would like to drop a ball into a test tube containing mixed corn starch and water ( in different ratios) and use Stokes law to get the viscosity for the fixed weight of the ball that I used. Would ...
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1 vote
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### How to calculate equilibrium height of tidal bulge?

I am trying to model the shape of the tidal bulge caused by the moon. I asked GPT for a formula and it gave me equilibrium tidal bulge height as $$\frac{2 R_{earth} G M_{moon}}{3 r^3 \Delta g}$$ and ...
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### Water pressure at the bottom of a box changes drastically depending on whether a water column above is connected or not? [duplicate]

(For the purposes of this question I'm ignoring atmospheric pressure completely) Consider a hollow cubic box with side length $1\text{m}$ that we fill up with water. Now suppose we make a small ...
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1 vote
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### What will happen if 10kg massed hydrogen ballon is released in air?

Generally, a hydrogen balloon would float when released in air, but what will happen when that hydrogen balloon has a mass of 10kg. Is it the density that decides whether an object floats in air or ...
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### Regarding angle of contact and capillary tube of insufficient length

It is written in my book that when a capillary tube is of insufficient length, the liquid does not overflow and the shape of the liquid meniscus changes, but the angle of contact remains the same. I ...
1 vote
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### What is definition of weight?

What is definition of weight? Does weight of an object change under water, or the weight remains the same, but the: 'apparent weight' = 'weight' - 'buoyant force' ? Same question for object submerged ...
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### Different types of pressure and their sources

I’m an engineering student. So far, I’ve learned about 3 types of pressure: Static fluid pressure ($P=\frac{F}{A}$). This wouldn't exist without gravity. I’ve solved problems related to the force ...
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### What is the meaning of screened potential? [closed]

I keep reading that it is supposed to account for the particle-medium interactions, but why do we need another potential besides the Coulomb one that includes the interaction between every particle in ...
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### How does a bubble pop?

I was looking at some old slow motion videos showing a phenomenon where a bubble is popped by firing a sphere (or pea) through it. One obvious thing that happens is that the pea does not pop the ...
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### Static Fluid pressure

Refrence:- If there is a weight force $Mg$ on a box of area $A$ then pressure on box will be $Mg/A$. In another case box is on ground in equilibrium, so there will be two equal and opposite forces on ...
1 vote
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### Using Bernoullie theorem to find efflux velocity

During the derivation of velocity of efflux Bernoulli's principle is used, $$P_A + \rho gH + \frac{1}{2}\rho V_A^2 = P_B + \rho gh+ \frac{1}{2}\rho V_B^2$$ My question is why $P_A=P_B=P_0$ = ...
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### What's the hydrostatic pressure inside a filled straw?

When we learn about atmospheric pressure in physics class, there's this classic experiment with a straw (second drawing above). So i wanted to ask about the hydrostatic pressure in that particular ...
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### What's the hydrostatic pressure in torricelli's experiment?

I've been studying fluid statics, and im getting stuck all the time trying to understand things that seem contradictory for example  the hydrostatic paradox or how a small force can be magnified in ...
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### Rotating fluid shape with its own gravity

Hi almost every student knows the rotating bucket with a fluid problem as described here: Fluid in a rotating cylinder I wanted to do the same for a rotating fluid in free fall (like in the ISS) to ...
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### Why isn't pressure change of liquid due to applied pressure dependent on liquid volume?

I understand that liquids are understood to be virtually incompressible, and so when a force over an area is applied to a liquid in a fixed volume container, the pressure change is even throughout the ...
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### Why does taking average pressure and multiplying with area given total hydrostatic force

I am not able to wrap my head around this. Why does taking average pressure and multiplying it with the area given total hydrostatic force? In many books, the reason was because pressure is linearly ...
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1 vote
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### Why is there no internal flow inside a fluid with stationary interface?

In fluid mechanics, consider a liquid with a free surface denoted by $z=h(x,t)$ (e.g. sessile droplet on a substrate). Suppose the free surface is subject to external forces acting in the normal ...
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### How can Ventury tube measure velocity in a pipe when it is is zero at the wall?

In the Venturi tube the sum of static and dynamic pressure is kept constant along a streamline. A reduced cross section leads to a reduced static pressure. $$p_1+\rho v_1^2/2 = p_2 + \rho v_2^2/2$$ ...
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### Mass/weight in 2 places at the same time

Though it may seem like it is not, this is a genuine question of which I cannot find the answer online. The situation of how the question arose may make it seem otherwise. I monitor my weight every ...
3k views

### How does pressure exist inside a drop of water?

Consider pressure inside a drop of water. I have seen a formula for it where $$\text{Pressure Inside}=\text{Pressure Outside}+2\frac{S}{R}.$$ I want to know how pressure exists inside the liquid. Is ...
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### Pascal's law vs buoyancy force in case of hydraulic jack

According to pascal's law as the pressure applied in a closed container will be equally distributed in all directions, we have a mechanical advantage of pushing the piston of large cross sectional ...
1 vote
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### A water-bottle demonstration of atmospheric pressure

I'd like to ask about an experiment on atmospheric pressure. To conduct the experiment, we need an empty PET bottle and make a small cut on the lower part of the bottle. A cut no greater than one-half ...
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### Approximations in computing pressure force on volume element

I'm trying to derive the formula for the value of the pressure force on an infinitesimal fluid element, with all the approximations usually thrown under the rug (at least in my textbooks) being ...
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