Two Hydrogen atoms covalently bonded to one Oxygen atom. One of the more common compounds on the surface of the earth.

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15 views

Explanation of a match between shadows and wet floor at Niagara Falls

The question is about the cause of a wet-floor phenomenon. My vacation trip started at Niagara Falls (Canadian side, horseshoe fall on the upper left corner). It was around 10-11 AM, not too sunny yet....
18
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4answers
2k views

Why does water feel cooler than air?

My first assumption was based on "evaporation causes cooling" but I realized that it is not the case as it is cooler even if I am submerged under it. Are all liquids generally cooler than air ? Just ...
0
votes
3answers
95 views

How much water did I actually drink? [on hold]

Water expands at temperatures over $5^\circ\mathrm C$ strictly monotonic. If you now drink $1~\mathrm{L}$ water ($5^\circ\mathrm C$) which will expand in your body on $37^\circ\mathrm C$, did you ...
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0answers
29 views

How much energy is released by decompressing water?

How much energy would be released if 2L of (relatively pure) water compressed to 1L at room temperature was suddenly decompressed to atmospheric pressure? Even a first-order approximation would be ...
2
votes
1answer
107 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, ...
2
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2answers
844 views

Dynamic water pressure from flow and diameter

I have to test some fire hydrants and need to get the dynamic pressure. For that I know I can use a Pitot tube but, I don't have one. After Googling a lot, I found two formulas allowing to compute the ...
1
vote
1answer
246 views

Does the termination point(level) influence water flow from a pipe

I get water to my home from a nearby Tank A at a certain height above ground level. I have a 1" pipe through which I get this water to my home.. I leave this water into my well by connecting a 1" tube ...
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0answers
13 views

Water Mist Problem? [on hold]

If a 150 USGPM 20 deg.C water in a 40 mm diameter with pressure of 25 bar need to be reduced to 2.5 bar through an orifice: will the water mist manifest?
3
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2answers
2k views

Changes in Water Bonding Angle

I heard something recently in a casual discussion, but have yet to be able to confirm it: is there any evidence that the bonding angle for a water molecule, currently defined as 104.5, has been either ...
10
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4answers
1k views

Hot water freezing faster than cold water

This question has puzzled me for a long time. There is already a question like this on Physics.SE. John's answer to the question seems quite satisfying. But when I googled the cause I found this and ...
24
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4answers
2k views

What is the status of Mpemba effect investigations?

There is this puzzling thing that is called Mpemba effect: paradoxically, warm (35°C) water freezes faster than cold (5°C) water. As a physisist, I've been asked about it several times already. And I ...
1
vote
1answer
40 views

What is absorption rate of WiFi and Bluetooth RF in water? [closed]

Specifically, frequencies 5.75GHz and 2.4-2.485GHz. I want to place a hermetically sealed circuit at the bottom of a gold fish bowl, and want to know if the water will significantly attenuate WiFi or ...
2
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1answer
545 views

Equilibrium between two water tanks

I've been reading about hydrostatic theory, however I couldn't find a similar case/exercise about my basic problem. I have two water tanks (same size) filled with different water heights, and ...
2
votes
1answer
27 views

How does infrared light behave through water?

I have a project involving the detection of the presence of water in a cylindrical transparent plastic container (diameter=25cm) And I cannot put any device inside, so I was thinking of using and IR ...
1
vote
1answer
121 views

Why does the bulk modulus of water have a maximum at around 60-70ºC

So I'm doing some water hammer analysis and was calculating bulk modulus of water as a function of temperature. I took the speed of sound and density of water as functions of temperature and ...
1
vote
1answer
39 views

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 ...
12
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5answers
1k views

What can wavy patterned sand tell about the Fluid that formed it?

Sand on the bottom of the ocean as well as sand on the low-tide beach often forms wavy patterns. Do the parameters of these wavy patterns have any relation to the water and waves that formed them? If ...
4
votes
2answers
490 views

What is characteristic time in Fourier number exactly?

What is characteristic time in Fourier number? How can I calculate characteristic time? Suppose I started heating water in a closed container by immersion rod and temperature increases continuously....
0
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2answers
75 views

Why does hot water freezes faster than normal water? [duplicate]

What is the reason behind hot water gets Freezes faster than normal water when we keep both the hot and normal water together in freezer ?
4
votes
1answer
266 views

Force field for calcium ions, potassium ions and water in molecular dynamics

I want to adapt my existing MD simulation so that it can handle these three species. For the interactions of the ions I thought that I would use the coulomb potential, but I don't know what sort of ...
2
votes
2answers
109 views

Submerged water jet

I am trying to calculate at what pressure and speed water from a high pressure water jet will hit an object 100 millimeters away from the nozzle opening, but i can't figure it out. The nozzle will ...
0
votes
1answer
292 views

Why is specific volume of saturated water greater at 1 MPA than at 0.1 MPA during the phase change process?

Why is specific volume of saturated water greater at 1 MPA than at 0.1 MPA during the phase change process? check out the T-V diagram here in the link. http://www.ohio.edu/mechanical/thermo/Intro/...
13
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2answers
422 views

Phase transition water

The water-gas phase transition is said to be similar to the ferromagnetic-paramagnetic phase transition (same set of critical exponents = same universality class). In the former case the order ...
4
votes
1answer
29 views

Why do individual clouds not diffuse into a single less dense cloud?

On a partly cloudy day, many individual clouds can be observed in the sky. I would expect that the moisture in the clouds would want to diffuse out into the other less dense non-clouded areas. ...
5
votes
4answers
201 views

Does salt speed the transition of water from ice to vapor?

In a dry environment that is somewhat below the freezing point, water ice will, over time, sublimate to vapor. If you scatter salt across the ice, some of the ice will melt, and the melted water will ...
2
votes
1answer
23 views

Bubbles in Hot Tub Jets

Ever since I was a child I have noticed a strange phenomenon in hot tub/jacuzzi jets, if you partially cover them, the water will still flow but the bubbles stop. No matter what hot tub I'm at, I can ...
166
votes
3answers
44k views

Surviving under water in air bubble

An incredible news story today is about a man who survived for two days at the bottom of the sea (~30 m deep) in a capsized boat, in an air bubble that formed in a corner of the boat. He was ...
35
votes
3answers
3k views

Why is ice made from boiled water clear?

A common trick to make clear water ice is to boil pure water prior to freezing it. Why does that work and what are the white inclusions in ice that was made from unboiled tap water?
4
votes
1answer
336 views

Fluid dynamics tsunami

I have been given a energy head (pressure) in meters for a given tsunami on land. If the tsunami hits a wall 1 meter by 1 meter, is it possible to calculate the height it will reach. I am thinking it ...
9
votes
1answer
17k views

How fast would someone have to run to run over water?

I was thinking about Flash, the superhero, or the little boy in the Incredibles. There is one Yahoo answer that doesn't answer a lot. Especially, I don't think surface tension would help a lot for a ...
0
votes
4answers
505 views

Does ice made out of salt water melt slower than ice made of pure water?

I'm trying to make this whole bunch of ice bottles to cool down my little aquarium. What I want in the ice bottles is that, fter freezing the whole bottle full water into ice, I need the ice to melt ...
3
votes
1answer
63 views

Is my thermometer faulty?

Today I decided to check my thermometer and measured the temperature of boiling tap water. The thermometer showed 98.5°C. The atmospheric pressure now is 742 mmHg. According to the Clausius–Clapeyron ...
1
vote
1answer
296 views

Is it possible to transfer water from a water bottle using condensation?

So currently I am travelling in a tropical country. I took my water bottle from the fridge and left it on the table, after a few hours it created a pool of water. Is this water from the outside air ...
56
votes
5answers
11k views

Why is water clear?

Water appears transparent to visible light, yet most other objects are opaque. Why is that? Is there an explanation why water appears transparent? Is water transparent at all wavelengths, or are ...
0
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1answer
21 views

Ball under the water jet

What is the name of the physical principle that show that a ball under a water jet (for example in a bathtub) rotates but does not move? I am not able to find any video of this
10
votes
1answer
1k views

Is there a temperature at which ice is denser than water?

Normally ice would float on water because its density is less compared to that of water as a liquid. But is it possible that its density will increase due to a very low temperature or is ice in any ...
8
votes
1answer
568 views

Calculation of water bulk modulus using equation of state

I simply want to calculate the bulk modulus of water at 50C and increasing pressures. I think I am correctly calculating the new specific volume from the original conditions at (25C and 1atm) to 50C ...
3
votes
6answers
15k views

How to measure resistance of DI water

It is known that good DI water have resistance ~20 MΩ·cm But how can I measure that? Using good vanilla ohmmeter (with 2000 MΩ range) showed crazy results (too low, not much dependent from distance ...
17
votes
4answers
612 views

Why does water ($\mathrm{H_2O}$) only have two distinct fluid phases?

Water (and other substances) can exist in many distinct solid phases (with different crystallic micro-structure), but only in two fluid phases - liquid and gaseous, in which the molecules are oriented ...
2
votes
6answers
32k views

Water pressure calculation for a volume of water at a given height

I'm looking to create a rain harvesting system. I have a 275 gallon IBC tote that is 48" x 40" x 46". I have an adapter for a 3/4 garden hose at the bottom of the IBC tote. I'm trying to figure out ...
0
votes
1answer
1k 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 ...
-1
votes
0answers
30 views

Hexagonal shape of snow flakes [duplicate]

As we know snowflakes has hexagonal shape. My question is why is that? and Is there any mathematical model which can explain that particular geometric shape of the snowflakes?
1
vote
3answers
334 views

Anchor of a boat

hope you can help I've been teaching my kids about pirates and when we were talking about pirate ships this morning I confused myself greatly. When carrying an anchor a pirate ship (or any vessel ...
1
vote
2answers
59 views

Force of water hitting a wall [closed]

If you had a 8" pipe with 500psi stream of water exiting it and hitting a wall at 90 degrees 8 feet away, what would the force of the water on the wall be? Thank you all. Non-mathematician.
0
votes
1answer
47 views

Calculate how much air will cool from an amount of ice? [closed]

So, there are $3kg$ of ice at $-18$ degrees Celsius and $50kg$ of air at $30$ degrees Celsius. I need to calculate how much the air will cool by the time the ice reaches its temperature. I thought I ...
1
vote
0answers
56 views

How was microscope-level zoom created by a lens and a water droplet?

It was a rainy night. My glasses were speckled with fresh water droplets. I looked at a distant street light and I was surprised to see cells - a single cell was zoomed in to the level where I could ...
2
votes
4answers
2k views

Riddle: can you swim faster upstream than downstream (with respect to the water)?

A friend of mine posed a riddle to me: A man swims upstream in a river, which is flowing at an unknown rate. He is wearing swimming goggles. At a certain point he loses his goggles. 10 minutes later ...
30
votes
6answers
15k views

Why does wet skin sunburn faster?

There is a popular belief that wet skin burns or tans faster. However, I've never heard a believable explanation of why this happens. The best explanation I've heard is that the water droplets on the ...
4
votes
2answers
113 views

Why is it easier to get sunburnt in the water? [duplicate]

I went today to the swimming pool and I remembered that when I was younger my mom used to tell me to be careful because you get sunburnt much more easily in the water than in the ground. I never gave ...
-1
votes
1answer
36 views

Water Boiling Time Calculator

Is there a way to calculate out how quickly a body of water will boil? My primary concern is to measure in relationship to different temperatures. For example, heat at 100 degrees Fahrenheit versus ...