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Questions tagged [surface-tension]

Surface tension occurs due to the tendency of liquid molecules to favor their own kind. Surface tension is important in fluid multiphase systems typically at small length and velocity

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Mercury Barometer

Why Mercury surface is flat instead of convex at 760mm Hg level in Mercury Barometer? refer the image attached. note that At top it is a vacuum and surface tension = (pi-po)r/2.
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Fast reversible switching from hydrophobic(>120 degrees) to hydrophilic (<60 degrees)?

I found few papers on reversible switching from hydrophobic to hydrophilic Reversible Hydrophobic to Hydrophilic Transition in Graphene via Water Splitting Induced by UV Irradiation Light-induced ...
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Diameter to prevent water flow into a closed-end tube?

Imagine I drill three holes of different diameter into a large block of plastic but the holes don't go all the way through. (They form three close-ended tubes, see the image.) I then submerge the ...
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Is this wire-melting phenomenon likely to be a manifestation of the Plateau–Rayleigh instability, and have I done my math right?

In LECTURE 5: Fluid jets from MIT's 1.63J/2.26J Advanced Fluid Dynamics equation 23 is $$\omega^2 =\frac{\sigma}{\rho R_0^3} k R_0 \frac{I_1(k R_0)}{I_0(k R_0)}\left(1 - k^2 R_0^2 \right)$$ and is ...
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Meniscus and capillary surface

Can anybody explain what the difference between capillary meniscus and capillary surface?
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How to get the height of a constrained, infinite elastic surface?

Suppose I have an infinite elastic sheet, constrained by several poles of height 1. The height of the surface would be 1 at the coordinates of each of the poles, and converge to 0 as the distance from ...
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When is the approximation of neglecting the surface energy most useful during estimating the total energy of a spherical system? [closed]

The bulk energy of a spherical system of radius R is proportional to its volume and the surface energy is proportional to its area. The surface energy per unit area, S, and bulk energy per unit volume,...
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How does different shuffleboard powder affect the disks' speed

I do know there is friction and surface tension involved here but am not sure on how exactly does different kinds of shuffleboard powder affect the disks' speed. So taking into the account the ...
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How does surface tension cause glass plates to attract?

I am having trouble with this example : As it says that the contact angle of the glass water interface is $0^{\circ}$ , so the force due to surface tension should act downward on the plates (rather ...
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Is there any material for which, on increasing surface roughness, changes from hydrophilic to hydrophobic or vice versa?

It is known that on increasing the surface roughness a hydrophilic material becomes more hydrophilic, i.e., it's contact angle decreases on increasing the roughness. Same is true for hydrophobic ...
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Contact angle of a thin film problem

I am having a hard time with problem 8 , so can anyone give me some hints. I'll say the things I have in mind I can use the Laplace pressure difference equation to find the the excess inside pressure....
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Trying to understand the derivation of the Gibbs adsorption isotherm

I have looked at several deritions online, and the clearest I have found is that on the Wiki page The problem being considered is that of two phases, with an interface of a given area between them. ...
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Does angle of contact remain constant for rise of liquid in a tube of insufficient length?

My book states that for rise of liquid in a capillary tube of insufficient length h * R (radius of curvature) = constant. Since the tube is of insufficient height radius of curvature increases to ...
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Maximum height of capillary rise

I know that when the tube is dipped in a liquid the rise is 2σcos(θ)/(ρgr). So the maximum should be when cos(theta)=1 but the answer is given c
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Could we explain formation of droplets by symmetry?

I have read at the free online book 'On growth and form' of Thomson D'Arcy that a cylinder has less symmetry than a sphere which is perfectly symmetric and that causes formation of droplets. But ...
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Does soap repel water?

Yesterday when I was taking my bath, I scratched my soap bar a bit and threw that bit on the shower floor. There was a little amount of water on the floor where that soap bit fell. To my surprise, I ...
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Determining the height of water level rise in a combined capillary tube

What will happen when we fix another capillary tube upon a capillary tube which has not enough space to its free capillary elevation?
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Why do soap bubbles seem to resist merging?

When playing with soap bubbles in a bathtub, it seems impossible to bring two bubbles together to form a single larger bubble. When two floating bubbles meet, a wall is formed between them. Even when ...
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On inserting a thin capillary tube into a large tray of water, does the total surface energy and the total potential energy of the system increase?

In both cases, the system is the liquid in the (tray+tube). I have made reasonably accurate calculations for the gravitational potential energy part. It follows from the calculations that the ...
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Theory or method on how to calculate the pressure needed to push a viscous fluid through a narrow slit

I need to calculate the minimum amount of pressure I need to apply to a piece of molten glass to start making it pass through a narrow slit - think 1 kg of glass and a 0.2 mm slit. At this point I ...
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How can I calculate for surface tension of a plate using formula γ=F/L with known force?

I am doing a lab to find out the change of surface tension of water as the temperature increase. I know the weight of the 2cm*2cm plate and the amount of weight required to break the tension. My ...
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Why does soap solution forms bubble but tap water does not? [duplicate]

The surface tension of water reduces on addition of soap to it. Then why does normal water not form bubbles but soap does even with less surface tension?
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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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Is surface tension a Conservative force?

Is surface tension a Conservative force? Can the work done by surface tension be recovered?
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Why does water always take an already travelled path? [duplicate]

I asked this question because I want a 'physics' answer. Now let me clarify the question. Assume that we let a drop of water fall on a flat surface. It should theoretically stay still. Now let the ...
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Why does water take a “wet” path?

Allow me to explain what I mean... ((I am asking this question in the physics section in hopes of finding a "physics" argument)) I shall make it clear what I mean by demonstrating an experiment... ...
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Sound emitted by droplets hitting a liquid surface

when a liquid jet (e.g. water) hits a water surface sound may be produced if, due to Plateau Rayleigh instability, the water jet has formed into droplets. But what exactly causes the sound? Is it the ...
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Why does liquid rise to same level in these different capillaries?

I'm having a doubt in the two types of approaches used to calculate the liquid rise in capillaries- one by the excess pressure method and the other by balancing weight of fluid column by the forces ...
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Does surface tension increase for a flowing fluid?

When a fluid is moving with velocity V, what becomes of its surface tension, does it increase or decrease in value
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Stopping overflow of boiling milk [duplicate]

We all know that milk overflows from the container when boiled. The reason is air trapped under the skin of the milk, can't escape and hence, pushes the skin upwards until it overflows. My mother ...
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What are the benefits of surface tension? Why is it so important?

I mean I read that surface tension is the property of a liquid by virtue of which liquid tends to have minimum surface area and behaves as if it was covered with a stretchable membrane. Why does a ...
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How fast does liquid rise in a capillary tube?

Take a small diameter tube, stick it in water, and surface tension will drive the fluid up through the tube. How fast is the fluid moving through the tube during this process? Here's my attempt: ...
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Curvature of fluid surface next to a floating sphere

I want to estimate the curvature $\kappa$ of the fluid surface next to a floating sphere. The situation is static and shown here: The fluid density is $\rho$, downward gravity is $g$, sphere radius ...
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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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Stable bubbles in a vacuum

I want to make space bubbles that hold some gaseous stuff - at very low pressure - for a long time and through nothing but surface tension. I can't use soap water as the water will evaporate quickly. ...
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Surface tension and entropy

I think of surface tension as work/area, just as pressure is work/volume. I understand it to measure energy rather than free energy. I should think that a molecule on the surface of a liquid would ...
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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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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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Problem in determinig contact angle of mercury in a glass tube

I am studying the contact angle of mercury and glass in glass test tube.I understood the water-glass contact angle but I am having confusion in understanding the mercury-glass contact angle. The ...
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Strange behavior of water flow

So recently when I was in a toilet, I noticed a strange behavior of the water that flowed down a nearly vertical pipe of my friend house. Instead of flowing straight down on the nearly vertical pipe, ...
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Surface Tension and Potential Energy in a Lagrangian

It seems natural to define the potential energy due to surface tension to be $U = \int \sigma dA$. But then I have the following problem. I wanted to investigate surface tension in a simple ...
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Why doesn't water actually perfectly wet glass?

According to many high school textbook sources, water perfectly wets glass. That is, the adhesion between water and glass is so strong that it is energetically favorable for a drop of water on glass ...
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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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How long does it take for oil to coalesce in water?

I was studying the process of coalescence in emulsions. We considered $N$ bubbles of liquid 1 floating in liquid 2. The result we derived, is that if there are some dissipative forces (diffusion) the ...
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What is the shape of a stream of water coming out of pipe?

As shown in the photograph below, when water comes out of a pipe (located on the surface of the earth) it travels downwards in an arc. What is the shape and size of this arc as a function of D, the ...
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Why do water drops form spheres in space? [duplicate]

When water is poured out in space, why does it always take a spherical ball-like shape?
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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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What keeps small mobile bubbles at the bottom of a kettle from rising

We have a glass jug water kettle with a flat heat plate as the bottom. It boils water quite vigorously in 2-6 minutes depending on how full with a 1000+W element. Just today I noticed that very ...
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Capillary force to move a mobile glass rod

Visualise a glass rod bent to form three sides of a rectangle. A second rod, free to roll on the two parallel sides on the rectangle, constitutes a fourth side of length l. If the apparatus is dipped ...
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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 ...