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Questions tagged [fluid-statics]

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95 views

Resultant force - Fluid Dynamics vs Fluid Statics pipe bend vs thrust force

After looking at a few examples between fluid statics and dynamics I am interested to know where the resultant force would be in the following example. A straight hose of infinite length containing a ...
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1answer
222 views

How to integrate pressure over a sphere?

if I had a function for pressure $P(y)$ dependent on $y$ (vertical position) and I had a sphere in a stationary position, how would I integrate the pressure differential over the surface of the sphere ...
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1answer
165 views

Explaining negative potential energy involved in Surface Energy of fluids

I was studying about Surface Energy in fluids, and here's what I was reading: (a) A liquid stays together because of attraction between molecules. Consider a molecule well inside a liquid. The ...
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1answer
42 views

Is it possible to drain all oceans' water to space? [duplicate]

Assuming: That I have an ideal straw (a very long pipe) from the ocean to space; That the straw (pipe) is ideal (will not break); That i can pump all the air from the pipe creating vacuum inside the ...
2
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1answer
51 views

When the barometer drops, my well level seems to rise - how?

I have a deep water well, with a length of 1/4" drip tubing, open at the bottom, taped to the pump 180' down. The other end of the tubing is connected to a gauge pressure sensor in the cabinet of my ...
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1answer
128 views

How to calculate the normal force of a box in the bottom of a bucket of liquid? [closed]

I have been trying for some time now, and seem to be unable to come up with the correct answer. The setup for the problem is as follows: After finding a similar question and rechecking the buoyancy ...
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1answer
59 views

In static fluid, pressure at same heights are equal. Is this applicable to the oceans?

Generally we consider the reference as horizontal line. But if we consider a vertical water column in the ocean. Then, if we want to consider the reference it should be a circular not a horizontal ...
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1answer
33 views

How do fluids behave in space with regards to bouyancy and density?

Will a fluid loose it's bouyancy in zero-gravity. What would happen if an object is immersed in a liquid in space (if the liquid is still very much together and not spilling as big bubbles or droplets)...
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0answers
68 views

If you try to pour water into a coiled hose as shown, no water will come out of the other end. Why ? (You should not connect it to a tap) [closed]

If you try to pour water into a coiled hose as shown, no water will come out of the other end. Why ? (You should not connect it to a tap). [J.Walker]
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1answer
74 views

Direction of excess pressure inside air bubble

What is the "direction" of excess pressure (or capillary pressure) inside an air bubble submerged in a fluid? Does it tend to act outwards towards fluid (from inside the bubble) or vice versa? My ...
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2answers
81 views

Pressure being isotropic

We say pressure is isotropic. At any point in a fluid pressure acts equally in all directions, but pressure is perpendicular force per unit area so how can pressure be there in all directions as ...
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1answer
37 views

Effect of temperature on specific weight

How much of an impact has a temperature difference when the specific weight of an object in water is measured, e.g. the weight of a mussel in seawater. Would the two scenarios yield the same specific ...
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1answer
62 views

Floating object and buoyancy force

A cubical object of side 100cm floats over a fluid of specific gravity 1.6. The depth of immersion is 75 cm. The centre of buoyancy lies 25 cm below the surface of the fluid. When measured from the ...
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0answers
24 views

Mathematical Demonstration of the Archimedean Principle [duplicate]

Can the Archimedes Principle be demonstrated mathematically?
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0answers
301 views

Hydrostatic pressure vs static pressure in a fluid

hydrostatic pressure is the scalar and isotropic pressure exerted by a fluid at rest at a certain point inside the fluid itself on the neighboring fluid parcels or on on an elementary differential ...
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2answers
171 views

Capillary length and Bond number confusion

The Bond number represents the ratio of gravity forces to surface tension forces, and is defined as $$ Bo = \frac{\rho g L^2}{\sigma}$$ where $\rho$ is the fluid density, $g$ is gravitational ...
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1answer
33 views

Will water spill out of filled capillary tube, if raised from water?

if to raise a filled capillary tube from the level of water, will the inside will spill out? or will it keep stuck inside? imagine a capillary tube put in water, the water rises inside the capillary ...
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1answer
66 views

Why does the pressure change on uniformly mixing two liquids?

The two cylinders are connected the upper cylinder has a cross-section of A and the lower one has a cross-section of 2A (I've taken the cross-sections to be A and 2A as they are easier to work with ...
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2answers
922 views

Floating of needle on water [duplicate]

An iron needle when placed horizontally on water, floats (sits) on the surface of the water. The phenomenon is usually justified as "surface tension". From what I understand, for the needle to float ...
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2answers
1k views

Why do bubbles initially stick to the side or the bottom of a glass while boiling?

When boiling water, I've noticed that bubbles will appear to grow at the bottom of the glass for a period of time and then rise. I've read that bubbles form from nucleation centers but I don't know ...
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4answers
1k views

Which weighs more in atmosphere, $1\,{\rm kg}$ of steel or $1\,{\rm kg}$ of feathers?

I'm having a discussion at the moment regarding the mass of $1\,{\rm kg}$ of feathers and $1\,{\rm kg}$ of steel. The person I'm arguing with states that $1\,{\rm kg}$ of feathers will be lighter ...
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5answers
2k views

If gravity accelerates all objects the same, why does a ball in water sink? [closed]

I recently learned the law of universal gravitation: F = GmM / d². It dictates that all objects should fall at the same acceleration. But how is density explained ...
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1answer
201 views

Why the body is drowning in the swamp?

Is it correct explanation why does the body sink? Swamp is not a liquid, but particle suspension, that's why Archimedes principle not working and upward buoyant force not applied to the body.
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8answers
6k views

Can a battleship float in a tiny amount of water? [duplicate]

Given a battleship, suppose we construct a tub with exactly the same shape as the hull of the battleship, but 3 cm larger. We fill the tub with just enough water to equal the volume of space between ...
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1answer
36 views

Why isn't right piston moving down even if a heavy car is resting on it?

I have understood the concept that pressure at same height should be equal but what about the weight of car that will also push the piston and pressure would change and left piston should go up, some ...
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2answers
47 views

Density of Sea Water [duplicate]

Understandably, there is a clear-cut difference between liquids and gasses. Gasses being more compressible, liquids less so. If you bring a volume of air sealed in a container from sea level to 10k ...
2
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2answers
110 views

Neutral buoyancy for cylinder/bladder in water

A 25 liter flexible plastic bladder consists of three parts: an air chamber located on top of the bladder, a large middle water chamber, and a lower weighted area that serves as a counterbalance and ...
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2answers
68 views

Movement of fluid in a container filled with that same fluid

If a cylinder with the bottom end closed and the top end open was filled with water and then dropped in a pool of water. Would the water inside the cylinder stay in the cylinder?
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2answers
58 views

Which of the two events will occur first

Consider a bottle partially filled with water and it is sealed from everywhere so that no air can enter or exit from bottle.Now make a small hole at the bottom of the bottle and hang it vertically so ...
2
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2answers
90 views

Reversibility of compressed air sinking in water

Consider an apparatus in which air is trapped in a small insulated container with an open bottom, and weighted with weights so that the air is slightly above neutral buoyancy. This apparatus is ...
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1answer
252 views

Stokes' law on non-spherical objects

So I have been thinking about Stokes' law and damped harmonic motions in a fluid. Now Stokes' law is only model on spherical objects and if I model this as a spring mass system and oscillate a ...
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0answers
96 views

Bernoulli's principle for a liquid with non uniform density

Consider a cylindrical container (section $S$, height $H$) which contains a liquid with non uniform density. Let $z$ be the axis along the height of the container ($z = 0$ indicates the top of ...
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1answer
126 views

Length of tube used in barometer is less than 76cm [duplicate]

In barometer the height of mercury in the inverted tube above the open surface level will be 76cm, if mercury is used. Now what if we take a tube filled with mercury but of length less than 76cm and ...
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1answer
93 views

What is the pressure under the lid of a rotating water bucket with lid?

Consider a water bucket with lid, the water is in contact with the lid and the lid is tight to the bucket The cross section of the bucket is circular, point A is the center of the circular section ...
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1answer
398 views

Can open-tube manometers be used to measure atmospheric pressure?

I was going through a slide made by my physics professor and was wondering about the statement made at the bottom: "This cannot be used to measure the atmospheric pressure". Why is that so? Given ...
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3answers
48 views

Attack point of buoyancy force

I have seen free body diagrams of submerged objects that show the buoyancy force acting on the centre of mass of the object. However, the buoyancy force arises due to pressure differences between the ...
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1answer
248 views

Laplace pressure of a capillary bridge

Laplace pressure is given by $$\Delta p=\gamma \left(\frac{1}{R}+\frac{1}{R'}\right)$$ where $R$ and $R'$ are the radii of the curvature of the surface. Using the following diagram the book I'm ...
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1answer
77 views

Why do we write pressure as $\frac{F\cos\theta}{A}$, and not $\frac{F}{A\cos\theta}$?

If you can follow from the diagram, the latter should be equally correct.
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2answers
56 views

Why aren't we pushed one left/right direction when we stand closer to one side of a pool?

Why isn't it that we are pushed more one direction left or right than the other if we aren't standing in the middle of the pool/ any fluid? By pressure=mass(height)(gravitational constant) and ...
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2answers
129 views

How is it possible to survive more than a few cm submerged underwater?

Suppose you hold your breath and dive a meter underwater. Assuming the surface area of the back of your body is approximately $1$ m$^2$, you have about $1$ tonne of weight above you. If you were out ...
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1answer
450 views

Pressure inside a bubble

Consider a bubble with radius $r$, inner pressure $P_v$, and outer pressure $P_{\infty}$. When we choose our control volume (blue dotted line in figure) to encompass half the bubble, we have a surface ...
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2answers
219 views

Would a human die from high air pressure at the bottom of the Mariana trench if it wasn't under water?

I read an article recently about gelatinous fish that live deep underwater, and if they were brought up to the surface would 'melt' due to the lower pressure not supporting their bodies. This got me ...
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1answer
166 views

Why does a fountain pen soak ink automatically at times?

I've had a rather interesting fascination with fountain pens. The mechanism is a thing of beauty, but my attention was recently caught by a rather insignificant phenomenon which I've used a lot in my ...
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1answer
88 views

Air Pressure in a Mine

In Sunday's "60 Minutes" TV program the correspondent descended into a gold mine said to be 2 miles (3 km) deep. What equation describes the air pressure relative to sea level atmospheric pressure?
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2answers
618 views

Why are the “bubbles” at the edges of my soup so large?

At lunch today, I was eating chicken noodle soup. After finishing most of it, I turned my attention to a sandwich and let the soup sit for about five to ten minutes. When I looked back, I noticed that ...
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1answer
20 views

Will hydraulics lever ever stop if we exert some force to it?

Suppose there is a simple hydraulics lever (like the one often shown when discussing about Pascal's Principle). If we exert some force into one of the piston without having any weight on the other ...
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4answers
317 views

Why can't liquids oppose tangential forces acting on them?

Also, when a glass of water is inclined at a certain angle, why does the surface of water continue to remain parallel to ground?
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2answers
511 views

Why does a liquid exert pressure in all directions? More specifically why does a liquid exerts an upward force? [duplicate]

In a liquid, the pressure is exerted by the weight of the liquid. As the force due to it's weight acts downwards, why is there an upward force at any point in a liquid?
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6answers
1k views

Why Pascal's Law is true and what is the mechanism for force amplification at molecular level?

"A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid" "A pressure change occurring anywhere in a confined incompressible fluid ...
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4answers
179 views

Can someone explain why there is water in this vacuum chamber?

I work at a water treatment plant that uses a vacuum system to pull the water into the filters and backwash the filters. In the middle of the vacuum system there is the vacuum chamber. What I don't ...