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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What are 'hydrophilic' spheres?

So, I know that a hydrophilic material is defined as those with a special affinity for water, opposite to hydrophobic, those that naturally repel water. I am investigating the impact of spheres with ...
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How is energy stored in the surface of a bubble?

In the book of Prigogine, Modern Thermodynamics, it is given on page 147 that Another example is the natural evolution of the shape of a bubble enclosed in a box of fixed $V$ and $T$. In the ...
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Why dont we consider the cohesive forces between the surface and inner molecules while formulating excess pressure inside a droplet?

As the surface of a liquid will have imbalanced cohesive forces leading to the phenomenon of surface tension,we just consider the forces among the surface molecules which act tangentially and dont ...
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How does even water rise along a glass plate?

So, I was studying about general properties of matter and topics like surface tension. I came across the phenomenon of water rising along a glass plate like in the picture. I looked for some ...
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Soap film bursting dynamics

Suppose I form a soap water film on a circular frame and poke a hole(with a pinhead) in the center, how will the circular hole formed increase in size with time (as the soap film bursts)? and does the ...
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Surface tension factor 2 [duplicate]

Can anyone please explain what is meant by this illustration when deriving the formula for the force of surface tension which is $2 L \sigma$, where $\sigma$ is the tension? Where does exactly the ...
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Why don't these water droplets fall? Is it because of the surface tension of the water?

Why don't these water droplets fall? Is it because of the surface tension of water? Under the action of gravity, water tends to fall, so the pressure at the top of the water droplet is lower than ...
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A oil drop is half immersed in water. What will be the direction of the force of surface tension on the drop? [duplicate]

Usually force of surface tension acts downwards , but in this problem , the direction is given upwards in my textbook. Am I missing a concept here , or the book is wrong? Please do help.
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Surface energy on different crystallographic planes

For a given crystal structure, say body centred cubic, on what factors does surface energy of each plane depend? A basic approach considers the atomic density on each crystallographic plane, the ...
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2answers
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Can surface tension be zero? [duplicate]

Inshort Surface tension occurs due to imbalance of the intermolecular forces of attraction on water molecules. At the surface it is more so net force is inwards. I read somewhere on this app that "...
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3answers
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Force due to surface tension in calculation of excess pressure inside a liquid drop

In the case of equilibrium of hemispherical drop, what i know is that the surface tension is responsible for holding the hemispherical drop with the other hemisphere thus forming a spherical drop and ...
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Why do we take two sides of a wire in case of calculating surface force of water? [duplicate]

When we have a wire on the surface of water, why do we take two sides of the surface of wire in case of calculating the surface force of water?
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Marangoni flow explained

Following this article, I want to understand more about Marangoni flow. So from what I get so far, there is a difference in temperature at a point in a solution and that create temperature gradient ...
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Can anyone help me describe the physics of my problem mathematically? [closed]

I was unsure if I should post this here or on the Mathematics page, so I decided to do both. Here's the problem I want to describe: Suppose I have a sphere, discretely represented by a large set of ...
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Mechanism behind capillary action

When we place a capillary tube in a beaker containing a liquid, why does the liquid level in the tube rise? Also, if it rises, won't there be a difference in the pressure at points A and B?( A is ...
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A question about Laplace law

In Laplace law, the force on a soap bubble from inside is $F = P.πr^2$ and what I understand that the leaning forces acting on the inside of the sphere are resolved into two components the vertical ...
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Direction of Force due to surface Tension

So I understand how surface tension arises: The molecules in the bulk of the liquid face forces from all directions, and their resultant is zero. The molecules on the surface, on the other hand, have ...
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257 views

Understanding the concept of surface tension

The concept of surface tension doesn't seem to be well explained in the first course on Fluid Mechanics. Fundamentals of Fluid Mechanics writes A tensile force may be considered to be acting in ...
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Gibbs free energy : is surface tension intensive and the surface area extensive?

As answered here Why Gibbs energy for nucleation theory?, one can write a surface Gibbs energy. Also, in the context of Laplace Law we have the variation $$dU=(P_{ext}-P_{int})dV+\sigma dA$$ leading ...
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Observed that under-water bubbles are very resilient: what causes this?

Noticed that bubbles could simply not be burst while underwater -- a bubble that was underwater with part of the surface touching the wall of the tub if pressed upon with a finger would simply move -- ...
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Why is meniscus formed?

Why does water tends to form meniscus (as it increases the surface area) if it has the tendency to lower the amount of free surface?
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1answer
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Squeezing water out from wet cloth

If a wet cloth is rolled together and squeezed or twisted, the water in it and cloth before soaking get separated. This is an everyday common life experience however the science behind it is not ...
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1answer
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Why does water fall sort of helically from a cup? [duplicate]

I noticed today that if I took a glass of water and poured it out slowly (small tilt to the cup), it flowed rather smoothly, but when I increased the tilt the water flowed in a sort of helical manner, ...
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1answer
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How to determine adhesive forces between fluid and a surface?

Disclaimer: I work in applied math and have limited background in Physics. Need a bit of help here. Assuming I have a 2D droplet attached to some surface like so: This droplet is also experiencing ...
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Why does dust form islands on top of water? [duplicate]

When you pour sand into water, first the dust particles that are floating on the surface, are separately all over. Then as the water flows, the dust particles should just randomly move around staying ...
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1answer
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Which direction a wooden cube would float in water? [closed]

If you place an uniformly dense wooden cube in water, would it float: face up vertex up edge up And why would that be the case?
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Surface tension and definition of boiling point

The boiling point of a substance is defined as the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. Does the pressure ...
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How can I predict if water will stick to the outside wall of a container when pouring at a certain angle? [duplicate]

I want to predict if water will spill while pouring it from one container to another due to it sticking to the outside wall of the pouring container and running down through it. I know the angle at ...
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2answers
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Writing pressure difference between water and air as a function of surface tension and second derivative?

In the context of a school project, I'm trying to redo the derivation of the Korteweg-de Vries equation. At the point where the normal free surface condition is combined with the effect of surface ...
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1answer
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Liquid surface tension and molecular motion inside

In some of the descriptions I have found about surface tension, while they explain the phenomenon for liquid in an open container they use the following arguments: 1) A molecule at the surface feels ...
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1answer
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How to measure the microscopic surface area of a textile?

How to measure the microscopic surface area of something like a piece of cloth? By microscopic, I mean on the level of fiber surface, not the area that would be measured by using a ruler on the piece....
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What will be the forces acting on the solid body in the two given cases?

I was reading the following paper by my guide and I encountered the following doubts. Consider the following two situations This is the case of the static contact angle. In this case, the solid ...
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When does water decrease or increase friction?

Water often acts as a lubricant e.g. a wet floor or road, but sometimes the reverse happens e.g. putting on wet clothes. I understand that surface tension is involved e.g. microscope slides sticking ...
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1answer
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Why doesn't mercury flow in the thermometer?

Nowadays digital thermometers are used, but in the past mercury based thermometers were used. From my experience the mercury does not flow in the thermometer tube. Mercury is a liquid, so it must have ...
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Droplets on surface tension

It's known how the fluid droplets dance on the fluid surface, and there are many slow motion videos or instructive video available in internet. Ie. The Slow mo guys Smarter every day When I looked ...
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Surface tension and Speed of capillary action

I have read that the height of meniscus in a capillary is directly proportionate to liquid-air surface tension. That left me wondering, is the speed at which capillary action occurs also ...
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1answer
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How can I reduce the surface tension to achieve realistic 1:43.5 scale waves etc

I want to achieve realistic flowing water instead of using polymers which produce static water. Ideally using a small wave making device to represent the sea.
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How to avoid water tension in a hose?

I am doing a project in which I have to flow water between two containers, which are connected at the bottom by a 1/4" hose. Remarkably, the surface water tension is such that water does not flow ...
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Increase the surface tension of polypropylene

I'm working on a project and I need to increase the surface energy of polypropylene. I want you to tell me a way in order to increase surface energy of polypropylene?
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Could situation where water does not pour out of a bottle change if different liquid is used [duplicate]

I was washing the dishes and came across a situation that was counterintuitive (at least from my perspective). The situation consisted of a bowl of water and a filled bottle of water. When I dip only ...
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What is the physical meaning of “critical crack length”?

There are two equations that are primarily used in context of the fracture stress one with $\sqrt{\frac{\gamma E}{a_0}}$and the other with $\sqrt{\frac{2\gamma E}{\pi C}}$.I do not understand which ...
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68 views

Surface Tension of Floating Object

I was reading this thesis about surface tension and its role in floating bodies. I couldn't quite understand at page 10 how the author applied the 2D divergence theorem outside the region bounded by ...
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What determines whether liquid droplets will combine or push into each other?

In trying to understand some fluid-dynamic principles, I am trying to discern between a couple water droplet interactions. This droplet video demonstrates the scenarios properly, but unfortunately ...
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2answers
106 views

Why Air bubble are always sphere in shape? [duplicate]

Everyone of us had noticed air bubbles once in his life. They are Sphere in shape. But I want to know why the are sphere in shape, instead of any other shape.
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Soap film bounded by a circular wire

If a soap film is bounded by two parallel circular wires, then the equation of its surface of the minimal area is $$ r=c\cosh(z/c) $$ where $c$ is a constant and $r=\sqrt{x^2+y^2}$. This can be ...
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1answer
92 views

Fluid pressure in Neumann's triangle for triple junctions

Consider a point of contact where three fluid phases meet. The Neumann's triangle rule for this case is usually written as, \begin{equation} \frac{\sigma_{\alpha\beta}}{\sin \gamma} = \frac{\sigma_{\...
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1answer
53 views

Does water have a minimal thickness because of van der waals force?

I have read this question: The thickness of a puddled sheet of water https://en.wikipedia.org/wiki/Surface_tension#Puddles_on_a_surface The liquid mass flattens out because that brings as ...
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1answer
233 views

How do I measure pressure inside a water balloon?

I have fill a ballon with water. The balloon becomes big for its elasticity. So a potential energy is been stored on the surface of the baloon that is giving pressure on the water inside. Now I need ...
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72 views

Why a drop of water acquires the shape of circle while getting absorbed on a bed sheet?

I am quite amazed by this observation as I couldn't prove it or intuitively have a correct reasoning for the circular geometry of the water drop which it acquires while getting absorbed on a bed sheet....
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342 views

Young's equation

Can somebody derive the Young's equation for the contact angle and surface energy of a droplet. $$\gamma_{la}Cos\theta+\gamma_{ls}+\gamma_{sa}$$ I've scratched my head for days finding how it exist....

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