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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Curvature due to changes in surface tension

What happens to curvature of a surface when the surface tension starts to decrease?
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General treatment of surface tension non-relativistic classical theory

I'm reading lecture notes on fluid mechanics course, and I wrote that an algebraic definition of surface tension can be constructed from work per unit area to balance the forces along the surface. ...
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What makes silicone sticky?

I've read from 3M's Adhesion Science articles and this StackExchange question that there are three types of adhesion: chemical, physical, and electrostatic. I'm curious about what makes silicone ...
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Requesting good reference to understand the Gurtin-Murdoch model of surface elasticity

I am searching for a good and understandable reference about the Gurtin-Mordoch model for surface elasticity. I was wondering if anyone can help me with the preliminaries and good references to fully ...
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Dual-medium Plateau-Rayleigh Instability

(This is my first question here so I would really appreciate your guidance on how to use SO better!) I’ve been working on the Plateau-Rayleigh instability for some time and I was considering the ...
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Nitro Brews and Sodas

I feel pretty sure this is a mechanics question, so here goes. I just finished a Nitro Pepsi - Yum! (I know, 63 grams of sugar. I had to brush my teeth twice after drinking it!) It is well known ...
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Confusion in Derivation of Excess Pressure in a Cylindrical Drop

I have recently learnt about surface tension and have developed a list of key points to solve problems:- Surface tension acts on the surface where a surface is defined as the interface(flat or curved)...
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Since surface tension and area are conjugate variables, is there a uncertainty relation between them? $\Delta \gamma \Delta A \geq \text{constant}$

Since all conjugate variables have uncertainty relations like ; $$ \Delta f \Delta t \geq \text{constant}$$ $$ \Delta \lambda \Delta x \geq \text{constant}$$ Etcetera, is there also a 'uncertainty ...
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What does a negative wetting tension $\delta F$ mean?

If a solid polymer has a drop of liquid (water) and shows a negative value of wetting tension, what does this mean? Does this mean that the drop of liquid will bead up instead of spreading on the ...
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A question about the form of Laplace law

Sometimes, I find some websites writing laplace law as: \begin{equation} p = \gamma\frac{1}{R} \end{equation} and some \begin{equation} p = \gamma\frac{2}{R} \end{equation} I can understand that the ...
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Why does surface tension on ANY body of water seems to have two discrete levels of roughness during light rain?

Here is a video of a flowing river during light rain. "This two levels of roughness" seems to occur on any body of water from a swimming pool to a large puddle in the street. Here is a ...
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Why does the shape of water flowing down from a squared orifice looks like a chain?

Hello I'm a high school student in Taiwan. My classmate and I are doing a project about the shape of water flowing down from a squared orifice, something like this video. We wanna know is there a ...
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Pressure Difference with respect to Surface Tension

Suppose we have a drop on a flat surface of radius $R$ and volume $V$. Then by a standard force balance argument we can relate the surface tension ($\sigma$) and the pressure difference ($\Delta P$) ...
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Change in Surface Tension of Inviscid Flow

If we have a stationary fluid assumed inviscid (and hence zero viscosity), it's well known that since there are no nonzero net resultant intermolecular forces on the fluids molecules, it possess' no ...
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Surface tension plot against time when a dry surface is kept on a wet one

Today I noticed an interesting phenomena, I kept a tea cup on a wet tea plate for long. When I picked up the cup again, it seemed like the plate was glued to the cup. By physical force, I seperated ...
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Are water molecules at the surface closer or farther apart than the molecules inside?

My lecturer says that since the energy of the molecules on the surface is higher (less negative), then at equilibrium there will be less molecules on the surface, hence the molecules on the surface ...
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Surface tension force between two wet objects

I have a problem related to surface tension. I hope someone good at physics can help me. The picture attached shows the two cases. I have an elastomeric sphere filled with air (compressible) and a ...
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Capillary and laplace pressure

How do I understand the difference between capillary and laplace pressures in the context of liquid interfaces?
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Getting particles to sink and stay in solution

I'm working on a project that involves finding moving particles in a solution (in my case, a syringe, or vial). The goal is to identify particles as small as 125um(micrometers), but the problem I face ...
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Having trouble understanding Re-derivation of Young’s Equation

I was going over a section 2.1 of this article (regarding Young's Equation and for some reason I wasn't able to derive E10 from E9 (see image below). I know it is more about the trigonometry of the ...
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Ability of some porous solids to tentatively sit on water for a while before sinking

How does a porous solid such as the cereal "Wheatena" manage to tentatively sit on water for a while before sinking? I assume it initially somehow evades capillary action, perhaps through ...
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Whats the fault in the logic I am thinking for not balancing of a needle and any blade etc. on water?

As we know that contact angle of water with any surface is approximately zero, so why a blade or a needle floats on water as such surface tension can only provide force parallel to the water surface ...
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Why does double edge razor blade not sinks but single edge razor blade sinks in water?

We often see that we can make a double edge razor float on water due to surface tension acting at some angle on all four sides to balance the weight i got this part , but when a single edge razor ...
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Surface tension and generalization of Laplace equation of a water droplet

The shape of a semi-spherical water droplet of radius R is given by Laplace law: \begin{equation} \Delta P=\frac{2\sigma}{R} \end{equation} I know the general Laplace equation is given by: \begin{...
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Surface tension caused by the Solid-Air interface and its direction

Contact angle of liquid in a tube-Wikipedia I'm a beginner studying microfluidic. I'm so confused about the direction of the surface tension. Like in the figure above, the direction of $f_{la}$ and $...
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Optics and capillary

In a small capillary of radius 0.5mm, the water inside raises by 10cm above the water surface. The angle of contact is 60deg due to some impurity which does not affect density or refractive index=4/3 ...
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Negative surface tension of de Sitter event horizon?

Questions – What does a negative surface tension of a de Sitter cosmological event horizon actually mean? Scotch in water, or something else? What does a zero ‘external’ vacuum pressure to the de ...
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What is the shape made by a half-filled ball?

An inflatable ball is made of a thin, inelastic, but bendable material. When fully inflated, it has a radius $R$. If the ball is filled half full with air, and is then continuously pushed underwater ...
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Which surface tension tension to consider in problems of liquid with solid interactons?

I came across a basic problem of finding height of meniscus rise of water, there the surface tension used for calculation was that of liq-air but my primary guess is liq-glass (solid) as that is the ...
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Why surface tension direction cannot be downwards in direction when considered the surface of fluid?

Like in this figure we see that the surface molecules have a net downward force to all of these so should any force which we made along a line on the surface the force be downwards ? Why the surface ...
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Are the forces between liquid molecules attractive or repulsive?

Surface tension is explained by there being attractive forces between molecules as show in the diagram. But shoudn't repelling or pushing forces exist for there to be hydrostatic pressure. How is this ...
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Water coming out of a capillary tube when height is reduced below initial level

Consider a capillary tube of height $H_1$. Water raises to a height $h_1$ in this tube. Now the capillary tube is cut such that its new height is $H_2 < h_1$. I've read in many textbooks and other ...
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What causes the rim of the droplet to stop moving in the Marangoni effect?

This is specifically concerning a set-up where a droplet containing a mixture of water and alcohol is deposited on the surface of vegetable oil in a petri dish. I want to know what causes the inner ...
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Teflon vs glass funnel

If you fill a funnel (with a long neck of uniform diameter such that pipe laws dominate the flow rate) with water while blocking the exit with your finger, and then measure the time for half of the ...
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Time period of an oscillating drop of liquid

We have a drop of liquid as shown, which is given a gentle push such that it begins oscillating, without tearing apart. We know surface tension $S$, density $\rho$, and radius $R$. I can't figure how ...
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Dimensional analysis of soap bubble formation

I was wondering how the radius of a soap bubble depends on the way it is formed and tried to come up with a simple argument using dimensional analysis. I am not sure if that argument if correct, or ...
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Liquid behavior in a rotating space station

For a novel I'm writing, does a liquid's surface (e.g. coffee) slope upward in the opposite direction to the spin of the torus in a space station such as in 2001? I'm guessing it does due to the ...
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How we can have 2 surfaces in thin film when we calculate intensity surface tension?

I have already seen that this question was asked earlier, but the answer is not specific. How is it physically possible that when the wire in this experiment can divide this liquid from soap into two ...
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What is solid_air surface tension?

I know that the liquids in general have surface tension, but when I started reading about contact angles I got confused and started asking myself the following questions: Why isn't surface tension a ...
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Surface Energy Dependence on Temperature

Surface energy is an energy needed to increase surface area of the interphase by unit or excess energy molecules have on the surface compared to the bulk. This means that surface energy will depend on ...
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Does the air density inside bubbles change with a change in bubble diameter?

As a bubble increases, there is going to be a change to the surface tension in the liquid-gas interface. Hence, as a bubble or to use the more precise terminology; micelle, increase in volume, will ...
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Why in a similar situation water falls of even though from other side no air can come inside?

In this video, Steve Mould mentions from 6:12 to 6:40 about how water tends to minimize surface area if we kept the one opening closed. Then why do we not observe the same thing when a water bottle is ...
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Molecular origin of solid-liquid and solid-vapour surface tension

I understand that surface tension arises at the liquid-vapour interface due to the asymmetric nature of long-range attractive forces and the short-range repulsive forces acting on the interface where ...
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Why is liquid air interface not counted during capillary rise

In the derivation of capillary rise, why is surface tension force only considered on the particles in contact with the capillary, all the other particles exposed to air only on the top forces should ...
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How do I correlate the Rayleigh-Taylor instability with this Marangoni Bursting phenomenon?

The droplet was a water-isopropanol mixture of concentration 50% and was deposited on a 5mm thick layer of sunflower oil in a petri dish.
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Why am I seeing a distorted boundary forming upon depositing a drop of 70% IPA on the surface of oil in a petri dish instead of a clear one?

I was trying to examine the effects of varying the concentrations of IPA droplets dyed with methylene blue on the phenomenon observed when they are deposited on an oil surface. I believe it is called ...
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Wetting liquids should NOT rise in a capillary tube according the gauge (Laplace) pressure formula. But they do!

In this image, the capillaries on the left-hand side contain a wetting liquid. Applying the gauge formula for the curved liquid surface we have $P_a-P_l=\frac{2\sigma}{R}^{*}.$ Where $\sigma$ is the ...
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What is this liquid flow behavior called?

Every morning, when I take a clean, dry metal tumbler and fill it with hot coffee, the first sip is always different than the rest that follow. The first sip requires some coaxing, for me to tip the ...
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Since the pressure in smaller bubble decreases why does its radius decreases and not increase, as it should, in the "communicating bubble" experiment?

If we blow two soap bubbles from two communicating pipes with funnels at the ends (see the fig) and close the tube to which they are connected, air will flow from the smaller bubble to the larger ...
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Why I require more force to slide covered notebooks over each other with water between them although water work as lubricant?

We have learnt when floor is wet we get slip as it reduce friction and work as an lubricant. But yesterday I take 2 notebooks which are covered by transparent sheet , than I pour little water on one ...
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