# Tagged Questions

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 do these experiments contradict the accepted theory about puddles? (+ my work)

A few months ago, I tried to tackle the problem of finding the shape, the height and other properties of a puddle (whenever a few mL of some liquid are dropped in a "uniform way" so that the puddle ...
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### Drop of water in zero gravity [closed]

Suppose there is a drop of water in gravity-free space. A man slowly touches the drop and keeps his fingers touched. What happens? Does the drop change its shape? Or wet his fingers? Or there is no ...
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### Water droplet lensing

Suppose I have a camera that is looking straight down at a single droplet of water resting on a flat surface. The droplet is small enough that surface tension forms it into a rounded shape. Inside ...
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### Surface tension between the glass slide and cover slip during wet mounting

When I was going through the chapter "Surface Tension" from high school physics, I read about surface tension acting on glass slide during wet mounting. It says that one free end forms concave surface ...
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### Does surface tension attenuate turbulence?

Rapids and several other "white water" systems could be typical examples of turbulent motion. To describe such flows the Navier-Stokes equations must be extended by terms describing the surface ...
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### Fluidics and surface tension

If a one cent coin is set carefully onto the surface of water horizontally (flat side parallel to the water surface). What are the relevant forces to determine if it would sink.
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### what is the mathematical expression of the water drop curve on the surface?

As a part of a high-school research about water drops on surfaces, I've been trying for a long time to find some theory that gives the expression of the curve, without any success. In fact, the ...
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### Water floating on water [duplicate]

In the video made by the slo-mo guys as shown here, at time 1:47 comes a moment when a water droplet(almost completely spherical), is seen to 'float' on the surface of the water for a while. So why ...
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### Tennis ball in a glass of water

If you pour water into a glass half full and put a tennis ball there it would aim to its sides. But if you pour water completely full a ball would aim to center. It's definitely related to a surface ...
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### How much of water's surface tension is entropic?

Water molecules on the surface of an air-water interface have preferred orientations that lower their energy. This implies that these molecules are not uniformly distributed in orientation space, ...
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### What are the dynamics of the “break the surface tension with a drop of soap” experiment?

There's a common experiment exemplified in the first few seconds of this video: https://www.youtube.com/watch?v=WsksFbFZeeU You put some food coloring in the center of a plate of milk, then put a ...
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### Why surface tension behaves so differently?

When a needle (or any other object) floats on water, its acting upwards balancing the gravity. But when an object (or may be a needle suspended in water) submerged in water, it acts downwards. ...
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### Can a droplet of water bounce back when it hits a water surface?

Is it possible that a droplet of water can bounce from the surface of a volume of water?
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### When does a liquid 'wet' a solid surface?

What is exactly meant when it is said that a liquid wets a solid surface. Has it got only to do with the contact angle ?
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### A question concerning ad/absorption [duplicate]

Why does a bone dry sponge resist ad(ab)sorbing a liquid whereas a damp sponge readily soaks it up?
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### What is the highest frequency for ripples on water

I want to transmit sound vibrations as ripples on water, as an experimental audio delay effect. Can I make ripples at audio frequencies, that will travel over about 10cm or more? How about other ...
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### Surface tension in a balloon wtih water [duplicate]

Imagine such situation: We have an empty balloon. We put a long, narrow tube into this balloon and we fill it with water. Then, the volume (and surface) of the balloon will start to increase. The ...
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### Why the Du Noüy ring method does not depend on the material the ring is made of?

Du Noüy ring method is a way to measure surface tension. Why the measured force, $$F= 2\pi \cdot (r_i + r_a) \cdot \gamma$$ does not depend on the material the ring itself is made of? Wouldn't a ...
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### What is the difference between pressure in water droplet and that in an air bubble?

The question is at least supposed to be simple but yeah, I need some detailed answers. I have tried thinking about it in the lines of surface tension but it seems what is required of me is more than ...
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### Which side of liquid gas interface is at high pressure?

With respect to what(whether liquid or gas) should I consider that the convex side has higher pressure and concave at lower prsseure? As seen in the example of image it is given that air bubble inside ...
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### percolation permeability threshold in Helium before and after lambda point transition

There's an experiment demonstrating the properties of super-fluid Helium compared to normal fluid Helium, in which the Helium is put in a jar who's bottom is porous. The super-fluid can pass through ...
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### Noncoalescingِ drops on vibrating liquid surface [duplicate]

if you set a dish filled with soapy water onto a loudspeaker or other vibrator and make vibration, When it oscillates, it is possible to hold small droplets on its surface for a long time. I mean, ...
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### Does surface tension play a role in planet's shape?

I'm thinking that when the planets and stars were forming along with gravity surface tension also could have played a role in making them spherical. Am I correct?
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### Surface tension: the paper clip experiment

In the paper clip experiment, the surface tension of water prevents the clip from falling, thus we can assume it exerts a force of $mg$ (weight of clip) upwards. However, if you try to pull the clip ...
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### why doesn't water in a inverted tumbler with its mouth covered with a porus cloth fall down ?

Is it due to the greater external atmospheric pressure acting upwards on the molecules or due to surface tension ?
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### How are probe liquids selected for Surface Energy measurements?

Why are water, ethylene glycol and diiodomethane generally used for surface energy measurement?
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### Why is a network pattern (weaving pattern) stronger than a whole solid surface of the same material

For example badminton racquets and huts.
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### Physics behind blowing soap bubbles

Is it possible, using the surface tension of a soap bubble, to calculate the maximum pressure (created by the air flow) it can withstand while still attached to the orifice to prevent it from bursting?...
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### Why rough surfaces promote nucleation of CO2 in carbonated drinks?

Glassware with scratched/etched surfaces generate more bubbles (video 1, video 2). Why these rough surfaces allow easier heterogeneous nucleation?
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### Explaining the shape of a raindrop and a drop of mercury

I saw on wikipedia that the shape of a raindrop is explained by using Laplace pressure. But why? Since the drop is in motion, we shouldn't be able to use an hydrostatic law, am I wrong? ...
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### Why do bubbles group when one pops? [duplicate]

I was recently observing the way bubbles move as they pop and disappear. I noticed that when bubbles destabilize and pop, the remaining bubbles immediately surrounding it will move to fill its place. ...
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### Torque and Force of Pulley fixed on side

If you had only 1 pulley that is connected to a rotating shaft, and which has a rope circled around it once, with a mass M on one side and with the rope fixed on the other end, how would you then ...
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### Beading of water on a hot surface

dropping water on a hot metal surface covered in dust results in the water forming beads. but if the surface is cold the water just flows over it. The temperature of the surface is roughly 120 degrees ...
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### Does eq. of continuity hold in vacuum too?

When a streamlined flow of water flows down through an ordinary tap, it's cross-sectional area decreases according to eq. of continuity due to atmospheric pressure. If the same apparatus were to be ...
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### How do impurities affect the surface tension of fluids? [closed]

I want to know what happens to the surface tension of fluids if we add impurities and the reason behind it.
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### Forces causing capillary rise

I have learnt two derivations to calculate the height of the liquid column in a narrow capillary. Here is a derivation using forces and equilibrium : This is the exact derivation given in my book. ...
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### Is surface tension characteristic of a fluid?

Does surface tension depend only upon the nature of the fluid or on other factors too like the liquid-solid or liquid-gas interface? I saw in my book definition that $$S = U/A,$$ where $U$ is the ...
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### Why is the liquid surface concave when it wets a container?

As you can see in this diagram the surface of the liquid is concave, why is the part of the liquid surface adjacent to the container has higher height than the rest of the surface, is it because it's ...
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### Gibbs isotherm and calculating interfacial tension change from first principles

Question: Is it possible for a solid particle to change the surface tension between two phases? (or: Does a solid particle have a chemical potential?) This question stems from the more fundamental:...
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### Why is there pressure difference when the liquid surface is curved?

I also want to know why such pressure difference do not occur when the liquid surface is plane even though there are different mediums at both sides of the surface.
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### Changing the Density of a liquid while its surface tension is constant

I'm working on Plateau-Rayleigh waves and I want to investigate the effect of density of the liquid on the wavelength of these waves How can I change the density of the liquid while its surface ...
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### Solving for diameter of a glass tube to hold water

I have a tube with length $l$. I then fill it with water. I then turn the tube upside down. What is the diameter as a function of $l$ such that the water does not spill out? I need to do a force or ...
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### Glass tube diameter to hold water when turned upside down

If I have a glass tube that is closed at one end and has length l, how can I find the range of diameters that the tube must be so that the water does not fall out of the tube when the tube is turned ...
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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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### 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 ...