We’re rewarding the question askers & reputations are being recalculated! Read more.

Questions tagged [fluid-statics]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
1
vote
0answers
40 views

How much energy is required to heat up a hot air balloon to make it neutrally buoyant?

To figure this out, I've tried to solve for $\Delta T$ for $PV=n_{cold}RT_{cold}$ and $PV=n_{warm}RT_{warm}$ which assumes that $PV$ is equal. This gave me the equation: $$\Delta T = \frac{T_{cold}^2 ...
1
vote
1answer
210 views

Why textbooks use geometric center/centerline of the pipe when calculating/measuring pressure?

Studying Fluid Mechanics, I started to notice that almost every textbook/website uses a specific point to make calculations about the pressure in a liquid at a given depth (hydrostatic pressure): the ...
1
vote
2answers
80 views

How do you explain the “weight” of helium?

If weight is measured as M * g (mass x gravity), then how does the "weight" of a massive helium filled balloon negative? Let's say you have a 63,000 m^3 helium balloon. The mass of the helium is ...
0
votes
1answer
61 views

How does buoyant force react with an acceleration $g$ load?

If a blimp with a certain amount of helium buoyancy accelerated enough to perform, let say, a +2G maneuver, would the buoyant helium force scale along with the weight force? All the mass particles ...
0
votes
1answer
211 views

Why using average pressure in calculations gives the most accurate results?

In the saga of trying to answer the question that came into my mind while studying the basic concepts of Fluid Mechanics, "Why textbooks use geometric center to calculate hydrostatic pressure when ...
1
vote
2answers
88 views

Moving air up a column without lifting

Say we have n sealed tubes segments $h$ in length, capable of withstanding at least 1 atm of pressure (this means that at a pressure differential of 1 atm, the segment will not implode or explode) ...
1
vote
1answer
32 views

What is the difference of pressure of a gas in a closed container at a given distance from the Earth?

If I have a closed container of a given height $(h)$, located at a given distance from the centre of the Earth $(r_o)$, what would the pressure difference be at the top of the container vs the bottom? ...
5
votes
4answers
3k views

Where is the right place to put the pressure gauge to measure the pressure of a tank?

Studying the basic concepts of Fluid Mechanics, applied to pressure gauges, and looking at schematics in many places, a question came into my mind: Where is the right place to put the pressure gauge ...
1
vote
1answer
141 views

Movement of a helium filled vs lower-density-gas filled balloon inside an accelerated car

It's well known that a helium balloon inside of a car moves forward when the car accelerates, and backward when it slows down. What would happen, though, if a lower density gas was used instead of ...
1
vote
0answers
125 views

When exactly can the concept of stagnation pressure be applied?

Although I've attached a homework problem here, I'm only using it for reference for a conceptual question on stagnation pressure. From my understanding, in the photo attached above, the pressure at ...
3
votes
0answers
101 views

Weird and unintuitive results from thermodynamics/hydrostatics for an isothermal atmosphere and possible explanation(?)

It is known from hydrostatics that for a fluid in equilibrium in a gravitational field, $$\frac{dP}{dz} = -ρg$$ Let us from now on suppose the atmosphere is isothermal and has temperature $T$. We ...
0
votes
4answers
642 views

Wood in water and buoyant force

Wood doesn't sink in water because its density is less than water density. So $ΣF=0$. But what is the force that counterbalances the gravitational force if the wood does not sink in water so that ...
1
vote
1answer
76 views

What is the physical meaning of static and velocity pressure?

According to Bernouli's equation, the static pressure inside a pipe with streamline and steady flow decreases with fluid's velocity. One explanation to rationalise this phenomenon is because velocity ...
0
votes
1answer
29 views

Gravity and objects in substances

This is probably a matter of terminology and me not finding it due to the lack of it. An apple falls from a tree on the ground due to gravity. Yet, if it falls into a water pit it floats on top of ...
1
vote
1answer
231 views

Why does Pascal's principle apply to a Hydraulic jack but not to stream lines in a stream tube?

Pascal's principle says that the pressure applied at one point in an enclosed fluid under equilibrium conditions is transmitted equally to all parts of the fluid and thus the pressure in e.g. ...
2
votes
1answer
60 views

Pressure on side walls of container [duplicate]

My textbook mentions the standard derivation of finding pressure at a depth of a liquid by considering a cylindrical portion of liquid an then using the equilibrium of forces and hence pressure comes ...
3
votes
2answers
594 views

Ice is in alcohol, if the ice melts does fluid level go up, down or stay the same?

The answer key says fluid level goes down. So, I understand the the ice would sink since density of alcohol is less than ice. However, I remember that when ice is in water and it melts, the water ...
1
vote
1answer
83 views

Champagne bubbles and gravity

One of the influences on bubble size is the speed with which a bubble rises in a glass - this, I believe, is due to the force of gravity which acts on the liquid around the CO2. The greater the ...
0
votes
3answers
80 views

Atmospheric Density

As I was reading my textbook, I noted that it stated that the atmosphere becomes less dense as height increases. I am unable to understand this. I understand that pressure decreases as height ...
1
vote
0answers
26 views

How to calculate the buoyance's work when releasing bar above water

The exercise is to calculate the buoyance's work when releasing a bar of mass $m$, lenght $L$ and cross section area $S$ just above water. My problem is that I am assuming my referencial on the water ...
1
vote
1answer
88 views

Hydrostatic force on spillway gate?

I'm designing an spillway gate that, as the water exceeds a specific height, then it opens pure mechanically, it means the hydrostatic force compensates for the weight of the gate. As you can see the ...
0
votes
0answers
117 views

Free falling fluid pressure distribution

Consider a free falling tank of fluid. The goal is to find the pressure distribution. My intuition says that there should be no pressure distribution; the pressure should be uniform since the ...
0
votes
2answers
45 views

The vertical component of surface tensions in wetting

To find the contact angle made by a droplet on a flat surface at equilibrium, we take the sum of all surface tensions at the boundary of the droplet to be equal to zero (Wikipedia link). Projecting ...
14
votes
5answers
14k views

If force is a vector, then why is pressure a scalar? [duplicate]

By definition pressure is the perpendicular force applied to a unit area. So it has a direction which is perpendicular to the area. So it should be a vector. But I did sone googling and found out that ...
1
vote
1answer
669 views

How to calculate speed of buoyant object rising

I'm looking for a formula to calculate the speed of object in buoyancy. Is there any formula available for this purpose? For example, if I release one liter water bottle from under 10 meter distance ...
-1
votes
1answer
520 views

Physical meaning of same pressure on the same plan (hydrostatic paradox) with different weight above them [duplicate]

In this picture the points on red have the same pressure because the weight of the fluid is the same above them. But according to pascal law the point on black must have the same pressure(both 3 ...
0
votes
2answers
106 views

Confusion regarding Archimedes principle

Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body ...
1
vote
1answer
560 views

How do speed and density change in a turbulent flow?

Suppose a fluid passes from having laminar flow, to having a turbulent flow (like when passing after an object). How do fluid speed and fluid density change after that?
1
vote
2answers
67 views

Physical meaning of variation of force of pressure with altitude in fluid

We usually prove that pressure is a function altitute Z. Imagine a cube in a fluid, then the force of pressure on the bottom surface is higher than the force of pressure on the top surface. But we don'...
0
votes
1answer
37 views

What is the force being applied? (Water Pump Problem)

Lets talk about the water pump problem where you must pump water up and out of a tank and figure out how much work was needed to accomplish this. So assume we have a cubic container with length 1 on ...
0
votes
1answer
158 views

Does venturi effect violate pascal's law?

If we use Bernouill's law to compare pressure between point 1 and point 2, we find that P(2)gdH=0, we conclute P(2)=P(1). I must have made a mistake but where is?
0
votes
2answers
72 views

Is it possible to generate energy by exploiting the hydrostatic pressure gradient?

Is there any way to harness the hydrostatic pressure gradient to generate energy? The pressure at the surface of an ocean is atmospheric pressure.As we descend down the ocean, the pressure increases ....
4
votes
2answers
234 views

Why is the pressure same in a horizontal plane in a static fluid?

One of the common explainations involve a cylindrical flask filled with fluid and Newton's second law. But such explainations is specific. What could be possible explanation in a case in which the ...
0
votes
1answer
258 views

Hydrostatic pressure in a gas

I have a physical picture of hydrostatic pressure ($dp/dh = \rho g$) in liquids, interpreting it as the weight of the water column. Now in a gas, the molecules are much further apart than in a liquid....
0
votes
1answer
67 views

Balloon rising up in water and reading on the scale

The balloon rises beause of buoyant force being greater than its weight, I'm interested in the change in scale reading while the balloon is still completely underwater. And let's ignore any viscous ...
4
votes
4answers
620 views

How can pressure act in both the up and down direction?

It says in my textbook that pressure is a vector. So how does it act both in the up and down direction in the same body of water as seen in this image?
2
votes
2answers
228 views

Archimedes Principle $\Delta M$ formula

i'm trying to determine a formula for $\Delta M=M-M_{apparent}$ in terms of $\rho_o , \rho_w , M$ for a fully submerged object and I have no idea where to begin. I have attempted to draw a force ...
0
votes
1answer
104 views

How to find velocity of water flow and $Q$ if I know static pressure at the end of the pipe of known diameter?

I have a pipe. At its end I have mounted pressure meter. Of course there is no circulation. Water pressure meter is a kind of stopper for water. I know diameter of the pipe, and I know its pressure in ...
4
votes
1answer
267 views

Is Pascal's law incorrect?

Consider the figure given below. Here I'm gonna talk about capillarity. The liquid inside the beaker as well as the column is water. As water has a tendency to rise in the capillary as shown, doesn't ...
1
vote
1answer
64 views

Would a conical siphon be able to lift water greater than 10.1 m?

In a discussion with my father, he argued that a siphon can only pull water up to a limit of ~33 ft (10.1 m). I understand that this limit would apply to water with a density of 1.0 g/cm at sea level (...
0
votes
1answer
70 views

Application of pascal paradox

My points of interests is at point A and B. I want to investigate how much pressure is acting on this two points. (Ignore Atmospheric pressure and work in gage pressure). Since the oil will flow up ...
0
votes
1answer
76 views

The link between two definitions of “potential density”

In Kundu's book , 4ed, P21, they define the potential density $\rho_\theta$ like this: However, later in P22, they define the potential density gradient as It seems to me that the potential density ...
0
votes
1answer
27 views

fluid statics doubt (regarding free body diagrams)

why does the pressure exerted by liquid on side walls increases with depth? please explain in detail.Thanks in advance
1
vote
2answers
81 views

What's measured by weighting a fluid?

Suppose you have a glass of water at room temperature. Now suppose you put the glass of water on a weighting scale. What the quantity actually measures ? I have read that in fluids are basically lots ...
-1
votes
2answers
936 views

Why should pressure be same at same height?

Suppose I have an U shaped tube, and I fill the left side with mercury and right side with water. Also I take another U shaped tube, and fill it with water completely, as shown in the below picture: ...
-1
votes
1answer
53 views

The other force in centrifuge

Consider a rotating centrifuge and a reference frame rotating with it. On every "piece" of fluid inside a centrifuge acts centrifugal force, but what are the other forces that make every piece stay in ...
1
vote
1answer
526 views

Torque exerted by pressure in a fluid

If I have a solid rigid body (let us call it a duck) in a static regime submitted to the forces of pressure $P$ of a fluid (no shear forces) I can easily calculate the total force $\mathbf{F}$ exerted ...
41
votes
3answers
7k views

Can ants walk on liquid mercury? [closed]

I'm not a physicist, but I was wondering: Can ants walk on dense liquid like mercury and why?
3
votes
1answer
638 views

Why can't hot air balloons fly higher then helium balloons?

I have read these questions: Hot air balloon trajectory predictions Do atmospheric physics prevent hot air balloons from ascending over 60,000ft? What is precisely the reason that a helium balloon ...
-1
votes
1answer
194 views

Height of a water tower, using Pascal's Law [closed]

This is a problem on Brilliant.org which asks, if you want to receive 400kPa of water pressure to a house that is at the foot of a water tower, how tall must the water tower be? It provides you with ...