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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Why is surface tension positive?

My book describes surface tension as $e=dW/dA$ and work as being negative when it is done against a force. Therefore, if i increase the surface area of a liquid i am doing work on the liquid against ...
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Why do sponges work? [duplicate]

By "sponge" I mean anything used to suck up liquids from surfaces, such as kitchen towels etc. I assume capillary action is a factor, and also maybe surface area and surface energy. What are the ...
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What is the direction of surface tension?

How do we define the direction in which surface tension will act? Surface tension is a kind of hypothetical tension in which liquid molecules undergo tension force at the surface. Thus it should be a ...
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Could a hydrophobic surface increase a liquid's resistance to compression/displacement?

Imagine a quantity of an aqueous (yet slightly viscous) solution is resting on a hydrophobic surface with a contact angle around 100°. A downward force is then applied as a (repellant) surface is ...
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2answers
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Are raindrops actually “shaped like tears” when they fall?

Raindrops are always pictured like this, people imagine they have this shape when they fall, but is this true? Doesn't this shape create too much drag? What shape do they really have? It would also be ...
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Thermodynamic derivation of condition for equilibrium of triple line

Edit:(4/1/2016) Okay, I get how the required equation arises from force balance. All forces are acting on the same length, so the length cancels out of the equation and what we've got is essentially ...
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Surface Tension and Its Direction?

Can Anyone explain what is the direction of Surface Tension? I studied it is along the Tangential plane to the surface e considered at the location of length element considered.. And within that plane ...
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34 views

What causes an emulsion to be stable or unstable?

The other day I made a salad dressing based on oil and vinegar. To my understanding, there is a positive energy associated with the surface between the oil and vinegar. The most stable state is also ...
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39 views

Does it take energy to destroy the surface of a liquid jet? [closed]

Imagine we have a collision of a liquid jet with an obstacle Does it take time for the surface of the jet to be destroyed while collision?? Or it'll be destroyed immediately?
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standing waves on a cylindrical jet

as we know, there are some perturbations on a falling jet which are always present and according to their wave number and the radius of the jet, they can grow and decay over time. so, imagine a jet ...
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Plateau–Rayleigh instability according to liquids $Ca$ number

For examining whether viscosity or surface tension dominates each other effects, we can't refer to $Re$ or $We$ numbers because they just tell us about one of them ( surface tension and viscosity ). ...
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Surface energy of water [closed]

If $10^3$ small drops of water each of radius $10^{-7}\,\mathrm{m}$ combined to form one single large drop then what should be the energy ? If the surface tension is equal to $0.07\,\mathrm{N/m}$ . I ...
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31 views

Plateau–Rayleigh instability for liquids with low $Re$ number

I'm working on a project about Plateau–Rayleigh instability for liquids. But I've a question. we can examine the fluids with high $Re$ number that the influence of viscosity is negligible, but what ...
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47 views

How does surface tension explain the floating needle experiment?

Part 1: After reading some explanation in internet I understood the fact that the molecules of water on the surface have no water molecules in the outward area so it feels a net force towards the ...
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39 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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1answer
45 views

What makes bathroom soap bars to crack during winter season?

Is there some relation between winter season and cracking of bathroom soaps? I noticed that , cracking happens only during winter season.I also learned earlier from physics stack that, During winter ...
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1answer
51 views

How to calculate the speed of a jet of liquid coming out of a nozzle? [closed]

I'm working on a project and i need to calculate speed of a jet falling from a nozzle. But my question is that, is it correct to use $$v=\sqrt{2gh}$$ Or should the speed of the jet be independent ...
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60 views

The Optics of the Vortex (in Water): why there is a bright ring also in reversed flow?

This question is closely related to this one; The optics of vortex (in water): why there is a bright ring? In this case "physics girl" gives somehow an plausible explanation, and it's only debatable ...
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How to make glass surfaces with different hydrophobicity level?

I have a number of small glass beads (d= 2.0 mm) and I need to use a method to make the glass surface hydrophobic. How can I create glass beads with different wettability levels (i.e. various contact ...
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1answer
38 views

What is meant by the word “length” in definition of surface tension?

Surface tension is defined as the force applied per unit length. What is that "length" belonging to? I can imagine force being applied per area but not length. "It would take a force of 72 dynes to ...
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1answer
30 views

Can a wheeled vehicle remain stationary on a water surface?

There are many field examples[1] of motorized, wheeled vehicles capable of staying on the surface of water. It appears that the requirement is sufficient "reverse-pressure" against the part of the ...
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2answers
91 views

How does a rising bubble take a dome-like shape?

Since I have swam on the swim team for most of my life, I am very familiar with bubbles. I know a raindrop falling through the sky gets its shape because it is the most aerodynamic shape, but how come ...
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3answers
100 views

Why sphere minimizes surface area for a given volume?

I was studying surface tension recently. Rain drops or bubbles of any kind which form are always of a spherical shape. This is because the liquid tries to minimize the surface area as the molecules ...
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Is there a conclusive correlation between viscosity and surface tension?

I'm working on a project and I need to know if the viscosity effects on the surface tension or not?
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How to measure the surface tension of a liquid in contact with air? [closed]

I've used some ways to reduce the surface tension of water in contact with air ( like adding oil or electrifying the water or .... ) but now I've a question. How can measure the surface tension of ...
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253 views

How to reduce surface tension of water?

I'm working on a project and I need to reduce the surface tension of water. I want you to tell me a way in order to reduce surface tension of water except changing the temperature.
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What exerts the force of surface tension, and what does it act on?

Let me start with the simple situation that I am familiar with. This question might be kind of long. I have just learnt that if we have an imaginary line on the surface of a loquid, the liquid on ...
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Shape of a water drop

Some years ago (1987 time frame), a mechanical engineering professor asked a question in a graduate level heat transfer class that I have never been able to solve. The questions is: "Given the ...
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26 views

Does nucleation depend on the rate of change in pressure in a carbonated liquid?

Carbonated beer flowing from a keg through a short length of tubing results in large quantities of foam. Unintuitively (at least to me), increasing the length of tubing results in a less frothy drink. ...
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How does surface tension and adhesion lead to this phenomenon?

Surface tension is the elastic tendency of liquids which makes them acquire the least surface area possible Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ...
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84 views

Magnetic Fields and Surface Tension of Water

Here's a research paper exploring the effects of a magnetic field on the surface tension of water. http://iopscience.iop.org/article/10.1088/1742-6596/156/1/012028/meta The conclusions were that ...
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27 views

What are the physics principles behind “amphibious” camera lens windows?

Underwater camera housings have a window through which the lens looks. When the camera surfaces, a couple of things can happen, and I've seen both captured in the camera footage. In one case, water ...
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55 views

Why don't we include the adhesive and cohesive force while calculating rise in a capillary tube?

The contact angle of a liquid solid interface is explained by saying that the liquid surface must be perpendicular to the resultant of adhesive cohesive and gravitational forces acting on it, since it ...
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85 views

Why is there a $1/2$ factor in the surface tension for a thin film?

According to Wikipedia on the surface tension of a thin film: $$ \gamma = \frac{1}{2} \frac{F}{L}$$ Where $\gamma$ is the surface tension, $L$ is the length of the movable side and $F$ is the force ...
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Formation of vortices in superconductors

So I'm trying to understand how mixed state of a type II superconductor becomes the energetically favourable state. I've been through a simple approximate calculation considering a S-N boundary to ...
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20 views

Should cohesion be considered as a resistant force here?

In some droplet generators, a pressure pulse is applied on top of a liquid reservoir connected to a nozzle and FIRST, a liquid jet is emerged from the nozzle and THEN, pinch-off of a droplet will ...
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67 views

Surface tension & capillary action

While deriving the equation of height to which the fluid rises, we say that the surface tension pulls the water till the weight of water balances it, my doubt is that how can any force pull on ...
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1answer
156 views

Turbulent and smooth flow of water from a tap

When water flows normally from a tap, we can say it is turbulent ( Pic 1 ). But when we attach a piece of cloth to the opening of tap, water flow becomes smooth ( Pic 2 ). We can say that by touching ...
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72 views

What is the surface tension of liquids in space?

I mean does surface tension exists in space on liquids? Let's take an example if I have to write something using ballpen in space and space does not have gravity. Does it works because of the surface ...
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2answers
186 views

Surface tension and capillary rise

The expression for the height rise in a capillary tube is well known, and the surface tension of the liquid air interface is involved. But as I understand the adhesion force between the water and ...
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455 views

How come a cork float to the side of a glass? [duplicate]

There's a not-so-recent video by a user named quirkology here, where he shows bets that usually work. From @2:19, he puts a wine bottle cap at the center of a glass ...
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1answer
71 views

Why does water remain as a “hemispherical bubble” when it falls on a page?

Today while drinking water, a drop of it accidentally felt on a page of my book, and I was thinking that, "Oh my god! The water will spread instantly, making the part of page wet". But, I observed, ...
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26 views

How can I estimate meniscus height and surface area of liquid metal in a crucible at high temperatures?

Is there any methods that can estimate the height of meniscus or the surface area of liquid (liquid metal) in terms of temperature, pressure, viscosities of liquid and contacting gas, and the ...
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Coffee Straw Physics

When I put my little, cylindrical coffee straw into my coffee, the liquid immediately rises about half a centimeter up the straw without provocation. This is also the amount of coffee that the surface ...
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1answer
83 views

Why small droplet goes upward after pinch-off?

This small droplet moves against gravity. How to calculate its initial upward velocity exactly after pinch-off?
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56 views

If the surface tension is reduced to half(say by using a surfactant), what would be the effect on the size of an air bubble in the liquid

If I reduce the surface tension to half of the original value, what would be the effect on the size of an air bubble in the fluid? What would be the effect on buoyancy and drag forces? Also, if I ...
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1answer
426 views

Why does surface tension of water-ethanol binary mixture decrease with increasing concentration of ethanol?

I was thinking that it must be due to weaker hydrogen bonding in ethanol than in water. But then I learnt that Raman Spectroscopy and viscosity measurements suggest that upto a certain ethanol ...
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2answers
136 views

Can a fruit fly move through a large bubble without popping it?

Assume what logistics you need to in order for something like this to be possible. Can a fruit fly move through a large bubble without popping it?
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391 views

Why is raindrop spherical in shape? [duplicate]

As the topic suggests why the raindrop is spherical in shape? Why it is not triangular or bipyramidal or tetrahedral? Is centre of mass or density of water related to it?
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When drying paint brushes washed with water, which way is the best to orient them?

After washing my paint brushes with soap and water and rinsing them, in order to avoid damage to the bristles and the ferrules and the wooden handle, is it best to hang them bristles down and let ...