The hydrostatics tag does also apply to fluid-statics.

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1answer
24 views

Consequences of general equation of hydrostatics $\nabla p= -\rho \nabla E$ in terms of surfaces where $p$ and $E$ are constant

I'm facing difficulties in understanding the consequences of the general equation of Hydrostatics in the case of conservative forces. $$\nabla p= -\rho \nabla E\tag{1}$$ Where $p$ is the pressure, ...
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2answers
40 views

$\nabla p=-\rho \nabla E \implies p=-\rho E +\mathrm{constant}$?

I'm not sure about the following mathematical passage. Consider the general equation of Hydrostatic in the case of conservative forces acting $$\nabla p=-\rho \nabla E \tag{1}$$ Where $p$ is ...
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1answer
23 views

The thickness of a puddled sheet of water

If I pour water of different amounts into a puddle on a level surface, it appears by eye that both puddles have the same height. The water seems to retain itself into a puddle by surface tension. I ...
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4answers
94 views

Why the pressure in liquids only depends on the height?

look at this picture : and also look at this one: imagine that the surface area of both is the same and both of them are full of water. My question is that why they both are pressing the beneath ...
3
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2answers
156 views

Is hydrostatic pressure independent of temperature?

Is hydrostatic pressure independent of temperature? Why only the weight of overlaying liquid is taken into account for calculating hydrostatic pressure and not the collision forces due to ...
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0answers
10 views

What liquid has the lowest known solubility of O2 at 20°C, 1 atm?

I have recently started a project on hydropneumatic devices, i.e. devices that use hydraulic fluids in conjunction with high pressure gases. In such systems, the most immediate thing you would want ...
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3answers
100 views

Physical explanation of Pascal’s Law

I have a problem with physical explanation of Pascal’s Law. For example, when I was teaching my sister (a high school student) about force transmitting by a rope, I said her: “In a very simplified ...
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2answers
44 views

Will it sink under circumstances? [closed]

I'm a 10 year old with a question. If you have a waterproof box the shape of a prism with an open top and you have a lid that fits perfectly in the top and you fill the box with water then put the lid ...
1
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1answer
79 views

If a hole is drilled at the bottom of a vessel, why is the pressure of the liquid leaving the vessel equal to atmospheric pressure?

My question is similar to this one : Should the liquid come out of the tank if a hole is drilled in the vertical wall? , but I still don't understand why the pressure within a free jet of ...
0
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1answer
66 views

What height is atmospheric pressure half that at sea level?

$PV = NT$, where T is a constant $P = \rho g h$ but I don't think this equation can hold in this form as the density is most definitely not constant as we go up in the atmosphere $\rho = ...
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2answers
27 views

Pressure question problem in forming the equation

A tank contains sea water of density $1030 \frac{kg}{m^3}$ The pressure at point M is $60 kPa$ more than atmospheric pressure. Calculate the depth of M below the surface of the water. My attempt: ...
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0answers
18 views

Water maintains equal level in connected vessels. What is this property called? [closed]

How water maintains same level in connected tubes or vessels? Is this a specific property?
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2answers
45 views

Helium Lift Potential [closed]

A particular mass of helium is required to lift a particular weight. If the weight stays the same and the mass of helium is decreased can the same lift force be achieved by increasing the ...
1
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1answer
53 views

Noncoalescing and bouncing droplets

if you set a dish filled with water onto a loudspeaker or other vibrator and make vibration, When it oscillates, it is possible to hold small droplets on its surface for a long time. I mean, when you ...
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1answer
116 views

Energy Conservation in Kinetic Power Plants [duplicate]

Quite recently the company Rosch has developed a new kind of power plant that supposedly utilizes the buoyancy effect to generate electricity. The apparatus consists of a vertical conveyor belt with ...
2
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1answer
61 views

$P = h \rho g$ derivation

Here is a snapshot from my textbook : Here only three forces are calculated: The gravitational force The force due to the pressure $p$ on the bottom surface The force due to the pressure ...
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0answers
18 views

general formula for water pressure

In a Sears & Zemansky Physics text, a general formula for fluid pressure is introduced. An infinitesimal element is created in the fluid with thickness $\mathrm dy$ and surface area $A$ at a ...
2
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2answers
73 views

Why do we take $h$ as “height from surface to bottom” when calculating liquid pressure?

In the following image, pressures of points x, y and z are $P_{x}, P_{y}$ and $P_{z}$ respectively, and they all are equal. My question is, why? The amount of matter on x is much more than amount of ...
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2answers
68 views

Difference between water and ethanol density for an object [closed]

I'm just slightly confused. Say that I had an object that floated 19.4m in water from the bottom of the object to the surface. Now I was going to change the fluid to ethanol, which has a density of ...
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3answers
32 views

Pressure and altitude

I am going to ask a simple question, for sure. The pressure with respect to the altitude is given by this formula Where sea level standard atmospheric pressure p0 = 101325 Pa sea level standard ...
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0answers
33 views

Acceleration of an bubble under the sea [duplicate]

An air bubble arises from the bottom of the sea. Find its acceleration if resistance force is proportional to $\rho Av$ where $\rho$ is density of water, $A$ is cross section area and $v$ is velocity ...
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0answers
23 views

A block floating on water is pushed inside until it touches the bottom. Will the block come back? [duplicate]

A block floating on water contained in a vessel is pushed inside until it touches the bottom of the vessel and then released. Will the block come back? Bouyant force acts because the pressure on ...
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0answers
15 views

Is there a relationship between maximum flow rate of a fluid through perforations in a cavity and the flow rate of the fluid in the cavity itself?

I have a scenario where water is flowing horizontally through a (rectangular) cavity. The underside of the cavity has a set of perforations that look something like: and I need to determine the ...
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0answers
11 views

Siphon and a pressure gradient

It's claimed here that the pressure gradient is what sustains the flow in a siphon. But I'm not really accustomed to the term and don't see why it forms and why it sustains the flow. Can you please ...
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1answer
34 views

How do you compute pressure at a pipe inlet if the pipe is leaking between the inlet and the outlet/pressure measurement point [closed]

This is a real world problem: I have a vertical pipe (a well ~800' deep); I have an unknown but reasonably fixed (artesian) pressure at the pipe inlet; I can only measure pressure at the pipe outlet; ...
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2answers
82 views

Is the force exerted by the container on the fluid and the force exerted by the liquid on the container equal?

I came across a question where i was asked to find the force exerted by the walls of a frustum shaped bucket on a liquid inside it . I found the force exerted by the liquid on the walls of the bucket ...
0
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1answer
77 views

What happens to the level of water when ice containing stone melts? [closed]

What would happen to the level of water in a vessel, when ice containing a stone, melts? If there was no stone, the level of water will not change. But when the ice contains a stone inside it ...
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1answer
51 views

Relation between Upthrust and Newtons Law [closed]

Using Newton's $2nd$ law of motion, show that when an object floats on the surface of water, the upthrust experienced by the object and the weight of object must be equal? The first thing is I don't ...
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0answers
55 views

Calculation of water pressure [closed]

I have a water tank of 750Ltr capacity installed at a height of 7.5M from ground. How to determine the range of pressure gauge required to measure the pressure from ground level.
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1answer
108 views

Using water pressure as pushing force in a floating bath tub? [closed]

Does physics allow for water pressure to work in this way? if so What formula can prove this? (backup link 1, backup link 2)
0
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1answer
34 views

I need to know the pressure of gravity feed elevated water tank [closed]

I have a rain catchment tank holding 5,600 gallons of water 7 feet above the ground. I want to run this water 20 to 30 feet to drip water plants. Currently a hose runs to a computer valve (timer) ...
0
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1answer
50 views

Difference of water pressure

We know that $P = \rho gh$, so is it true that water pressure at 2nd floor will be higher than water pressure at 9th floor of a 12 story building?
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1answer
57 views

What does Low Surface Tension mean?

I have that a book that says "Low surface tension of a liquid helps it to spread over a larger area." . My question is How and Why ? When I say that a liquid A has a lower surface tension than liquid ...
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4answers
5k views

What is the energy source if a tall water tank is used to transfer floating objects upwards instead of cables with motors?

Suppose I want to transport some logs from the ground to the roof of a tower. Originally I can use a lift, or some cables, or even move the logs upwards manually; then the energy is converted to the ...
3
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2answers
172 views

Pressure change when closing valve inside a column of water

Main question: If you have a column of fluid with a valve as shown on the drawing, what happens to the pressure at the point p when moving from state A to state B ...
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7answers
2k views

How to keep a helium balloon between 1 to 5 meters above ground? (without it being tied)

I understand that helium balloons rise because their density is less than air, so they can rise up to a point where the air surrounding it has the same weight as the balloon. I was thinking to fill it ...
0
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1answer
64 views

why don't we consider atmospheric pressure or weight of liquid while deriving the equation of thrust in a fluid?

More specifically , when we try and prove that up thrust experienced by an liquid column inside the liquid is equal to the weight of the liquid column , I have seen it being derived like this: thrust ...
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2answers
51 views

Is Buoyant force a reaction?

When we fall on water. The surface molecules are pushed down and as a consequence molecules below the surface molecules and molecules beneath them and so on are also pushed down. Some of them are ...
2
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1answer
186 views

How does hydraulic press work at molecular level?

Let's consider the following arrangement: I know that because of conservation of energy the force on the car has to be amplified. The work $W$ done is $$W = \text{Force} \cdot \text{distance} \, ...
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0answers
30 views

Liquid pressure confusion

Water molecules are free to move around and they collide with the walls of the container in which they are kept.So,as a result they should exert pressure on the walls.But, while calculating force ...
0
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1answer
62 views

Doubt in the concept of Upthrust and Buoyancy

First of all, we know that $P = hρg$ for any depth h in a liquid. While deriving this formula we use (mg + P1A) - P2A = 0, where P1 and P2 are pressures on the upper and lower surfaces respectively. ...
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2answers
145 views

About the real reason why paper doesn't fall in HALF-FILLED inverted cup [duplicate]

I just happen to see a show about air pressure host by Brian Cox. As the link:http://imgur.com/EsRadFi shows, he flipped a half-filled water cup upside down then the paper on cup doesn't drop: It ...
4
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2answers
228 views

Why do helium balloons rise and fall?

I understand why a regular party balloon filled with helium falls over time due to leakage of the helium. However I've also noticed that recently filled helium balloons put outside rise and fall. At ...
1
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1answer
37 views

Flotation of a body which is submersed into a incompressible fluid using Archimedes principal [duplicate]

There is a small boat in a water tank and the boat is loaded with a huge piece of rock .The water tank is totally filled with water .If the rock is taken off from the boat and totally submerged in the ...
0
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1answer
62 views

The Direction of Pressure Gradient in Hydrostatic Equilibrium

The equation for Hydrostatic Equlibrium in galaxies and galaxy clusters is quoted as: $$\frac{dP}{dr}\times\frac{1}{\rho} = -\frac{GM}{r^2}$$The minus sign on the right hand side indicates that the ...
0
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2answers
55 views

Finding the work done to fill the tank by pumping water over the edge? [closed]

I am really confused on how to approach the following question and how to set it up. So the question is: An open tank has the shape of a frustrum of a right circular cone. The tank is ...
4
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3answers
601 views

How can the atmospheric pressure be different in distinct points at the same altitude?

From an hydrostatic point of view, the pressure in a fluid should be the same at the same depth/altitude. Obviously, in our atmosphere that does not happen. I am guessing that the main reason is the ...
4
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2answers
131 views

Water bombing - risks and possibilities

I just saw a video on youtube, where an excavator drops a load of water on a car, destroying it completely. I also saw a video with a fire-fighting plane dropping even more water on a burning truck. I ...
3
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2answers
134 views

Why buoyancy is applied on centroid?

My book says: "The point of application of the buoyancy force is the geometric center(centroid) of the submerged part of the body, whereas the specific gravity of the fluid is constant." But why ...
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1answer
214 views

Questions on Pascal's Principle

I am aware that Pascal's principle says that if a pressure acts on an enclosed liquid, the pressure will be transmitted uniformly throughout the liquid. Can Pascal's Principle be applied to a ...