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Questions tagged [fluid-statics]

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Trouble in forming force balance equation for a submerged cylinder [on hold]

The question states that, when the liquid level is at a height of h₁ above the wooden cylinder, the cylinder is about to start moving up. What is the value of h₁ in terms of h? My attempt at this ...
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3answers
77 views

Why can water be sprayed farther when the pipe outlet is narrowed?

Someone told me: This is because the flow rate remains unchanged, so the flow rate of small diameter pipelines is faster. I don't think this explanation is right: the diameter of the pipe outlet is ...
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2answers
33 views

Which way does the fluid flow? [on hold]

In the given siphon arrangement if a hole is made at D, will water leak out or will air leak in? I think air should leak in as fluids flow from high to low pressure but I'm not sure... Any help ...
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1answer
47 views

Buoyant force when object is between two liquids

Suppose we have a ball floating in liquid A. Then we pour a liquid B on top of the ball (Assuming that the liquid is poured such that the ball doesn't oscillate) . The ball rises up. Why? According ...
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2answers
698 views

Does capillary rise violate hydrostatic paradox?

If $p$ is a pressure and $p_A = p_{\text{atm}} + hdg,\,$ $p_B = p_{\text{atm}}$, is hydrostatic paradox violated, shouldn't $p_A=p_B$?
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2answers
60 views

Bernoulli equation: how should one imagine $\frac{p}{\rho}$?

The Bernoulli equation states the following $$ \frac{1}{2}u^2 + \frac{p}{\rho}+ gz = \text{constant along a streamline} $$ where: $u$ is the fluid flow speed at a point on a streamline, $g$ is ...
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3answers
43 views

What is the physical origin of buoyancy?

Imagine a horizontal cross-section $\Delta S$ of a cylinder containing a liquid of density $\rho$. The downward pressure on $\Delta S$ at the depth $d$ from the surface of the liquid is $P_{down}=\rho ...
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1answer
17 views

Horizontal force on a fluid surface

I was doing some problems involving calculating the thrust due to pressure on curved surfaces. One way, of course, was to integrate over the surface to find the thrust. I noticed that the answer ...
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1answer
26 views

Buoyancy and Archimedes Principle [closed]

One kilogram of wood (density ~0.8 gm/cm^3) and 1 kilogram of aluminum (density ~2.7gm/cm^3) are dropped into a pool. Which has the largest buoyant force on it?
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3answers
57 views

Fluid mechanics - pressure [closed]

We know that pressure inside a container depends on depth. My question is that if this true then if I fill water in a one end closed pipe which has diameter of 2cm and height is 4m and if I fill the ...
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0answers
73 views

Why does P = $\rho$gh seem to contradict equal accelerations of fluids in a closed U tube?

This is based on a problem. The closed U tube is as shown : I want to figure out time period of small oscillations if the liquid interface is slightly disturbed. My take : considering an ...
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2answers
45 views

Hydrostatic Paradox - weighing issue

In the picture below, both tubes have the same pressure at the bottom. I understand that if they were weighed individually, they would show a different result since the water on the second tube is ...
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1answer
28 views

How to calculate the specific weight of air?

First of all sorry for my bad English ... I have to calculate the specific weight of air knowing that in the air there is actually a small percentage of water vapor. Therefore the specific weight of ...
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1answer
21 views

Is there a relation between the pressure at a point in a fluid and the pressure on the surface of a horizontal object placed at the same point? [duplicate]

So if the pressure in a large fish tank 10 meters below water surface is 50 Glitches (didn't have a realistic number so I put an unrealistic unit), and a Pancake batfish stands still there for a while,...
0
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1answer
41 views

Drinking Straw physics [duplicate]

I was just wondering, when you put a straw in water and block the top, water doesn't get out from the bottom when you lift it up. What about alcohol like Vodka ( ethanol )? I am trying to make a ...
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1answer
18 views

Forces in a hydraulic lift

My answer states that the force applied is the same for 1 and 3 but less than the one in 2. I understand why 2 is greater than 1 but do not understand why 1 and 3 are the same when 3 has double the ...
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0answers
25 views

Integrating to find net pressure and force on a sphere by a fluid

How would I go about solving for the net force on a sphere exerted by air pressure as a result of pressure being dependent only on the vertical position of the ball? When the sphere it is placed in a ...
-1
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1answer
44 views

Potential energy of ice cube is container dependent?

The potential energy of an ice cube floating at sea can be measured from the surface of the water, which remains at a constant height as you drop the ice. However, what about when you drop it into a ...
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2answers
20 views

Fluid statics - buoyancy force problem

The pictures above show the question and soution. The part I don't understand is why the air pressure is acting upwards against the plate instead of downwards on the water. Could someone explain this ...
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0answers
26 views

Can an ideal fluid be at rest in a non conservative body force field?

We know that, when an ideal fluid is at rest, then the body force density is equal to the gradient of the pressure. But, that means body force should be conservative. So, does it mean fluid can't be ...
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0answers
27 views

Derive the virial theorem from hydrostatic equikibrium

Consider the equation of hydrostatic equilibirium as follows as applied to a stellar object: $$ \frac{dP}{dr } = \frac{-GM\rho}{r^2} $$ I know it is intimately related to the virial theorem but I ...
2
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2answers
116 views

Bouyant Force Confusion [closed]

I was asked to solve the question in the picture I naturally thought the answer was (1) because bouyant force is caused by the pressure difference on the object's top and bottom surfaces. Turns out ...
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2answers
21 views

Hydrostatic Condition in Fluid

If we provide constant velocity to the partially filled container then the liquid present in the container is in the hydrostatic condition or not. I think since velocity is constant then there is no ...
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0answers
28 views

Derivation of height of a liquid in a capillary tube

I was going through the derivation of height of a liquid in a capillary tube when I came up with a doubt...although its a very basic doubt and you may laugh at it...but please help me...I was thinking ...
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1answer
51 views

Why we consider pressure do not vary with height incase a gas in a vessel?

Why pressure do not vary with respect to height incase a gas contained in a vessel and atmospheric air pressure varies with respect to height. for example we consider constant pressure in a mercury ...
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1answer
58 views

Why is pressure greater at the bottom end of a box submerged in water?

It is my understanding that the pressure acting on the bottom end of the box would be greater than on the top. But if we place a box under water, then the height of water above the top end of the box ...
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1answer
35 views

Bouyancy of ozone gas

If ozone is $O_3$ why is it an outer layer of the atmosphere? It seems $O_3$ would sink in a solution of $O_2$, rather than float on it.
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2answers
63 views

If I immerse a coin in a cup of water, help me define the forces acting on it

So the coin is hanging in an equilibrium position midway in the water filled cup, concerning the force acting on the upper face of the coin, I define it as F=mg where m is the weight of the water ...
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0answers
28 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 ...
0
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1answer
76 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 ...
0
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1answer
50 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
39 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
44 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
69 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 ...
0
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1answer
41 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
28 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
62 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
27 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
51 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
33 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
51 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
23 views

Mathematical Demonstration of the Archimedean Principle [duplicate]

Can the Archimedes Principle be demonstrated mathematically?
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0answers
69 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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1answer
48 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
22 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 ...
3
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1answer
43 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
120 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
687 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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3answers
686 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
1k 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 ...