# Tag Info

1

The mechanism by which lightning is produced is complex and imperfectly understood, but we know moisture is important in two respects: Heat is released when water vapor in the air condenses into liquid drops, and this heat helps provide energy to the thunderstorm. Interactions between supercooled liquid water droplets and ice crystals in the upper ...

0

Well, this seems pretty easy to treat as a Fermi problem. The heat capacity of magma (and rock in general, I suppose) is about $2\;\mathrm{kJ}/(\mathrm{kg}\cdot \mathrm{K})$. The heat capacity of water is about $4\;\mathrm{kJ}/(\mathrm{kg}\cdot \mathrm{K})$, and it's latent heat of vaporization is about $2000\;\mathrm{kJ}/\mathrm{kg}$. The total volume of ...

1

I am not aware of a better name for this sort of point in the scientific literature. It doesn't exactly shock me if you refer it as an eutectic point, but you'd have to explain it in its first occurrence in the text. Otherwise, just assign a letter to it (just avoid “lambda point”!), and use that throughout your paper.

0

The speed of sound is only about 0.1% - 0.6% faster in dry air than in humid air at the same pressure and temperature, but humid air is also less dense than dry air, so my best guess is that the vibration from the wires couples less strongly to air that has moisture in it than it does to denser dry air.

5

The noise is either from the AC electricity, which would be a 60Hz buzzing, or from small bubbles forming on the heating element itself. When the electricity stops, both the buzzing and the bubble formation will stop as well. Bubbles create sound due to quickly expanding from a small nucleus. Here's a book I found with a section on noise from bubble ...

0

This can be treated by use of Bernoulli Equation, which says that the sum of geodetic, dynamic and static pressure is constant for every flow cross section of a frictionless fluid system. On top of that, friction can be accounted separately and represent the other side of the Eqn.. For the fluid part, friction factors depend on Reynolds Number and geometry. ...

0

in the end whater and milk and all containers will be at the same temperature, it's just 10 mins wasn't enough. the heat exchange is proportional to the temperature difference. so when milk is very hot the heat exchange from milk to water is fast, and it slows down as milk cools down and water heats up. they can meet somewhere in the middle at temp higher ...

1

As DavePhD has explained, the water would never be warmer than the metal. As you waited a long time, you can safely assume they are at the same temperature. But, why do they feel different? Your hands are warm, and when touching a thermal insulator, such as wood, they will quickly transfer energy and heat up the surface of what you are touching, so it feels ...

0

"I never understood is water continuously absorbing heat from the milk glass even when the water itself gone warmer? I thought they should ideally be at the same temp at the end.": Yes, the water will continuously absorb heat until there is no temperature difference. However, the rate of heat transfer will continously decrease. The rate of heat transfer ...

0

I don't think that the size of the hole has an influence on the energy required. Friction is a complicated matter here, not easy to calculate. Try to calculate the pressure imposed by the water on the piston. The force working against that pressure will require most energy. Edit The pressure on the piston isn't uniform along its height in this case. At ...

0

Hint: What potential energy does the water have with respect to the heigh of the container valve?

0

Any system in which hydrostatic pressure is not the only pressure to consider could sustain a water level difference between connected containers. To give an example: a system that isn't at a static, but rather a dynamic steady state can have unequal water levels. Think of two containers with one (tank 1) elevated above the other and a two hoses connecting ...

1

Whenever it seems like two water levels should be equal but aren't, either there is a physical restriction preventing flow (like a dam keeping upstream waters higher than downstream, or surface tension causing meniscuses or capillary action), or there is energy being expended to put water back upstream as fast as gravity is pulling water downstream. In a ...

0

If the water is frozen - it won't equal out. If the containers are not connected - it won't equal out. If water can't reach the connection equally easily from both containers - e.g. if the connection is high or low and the water is vapor - it won't equal out.

4

The correct answer is that Surface tension prevents the formation of small water droplets. You see, as the surface energy is proportional to the droplet area ($r^2$) and the bulk energy - to its volume ($r^3$), their ratio ($1/r$) will rise to infinity as the droplet radius $r$ goes to zero. Therefore, the droplet cannot grow steadily from $r=0$. Even below ...

1

Solids are very good conductors of heat compared to liquids and gases. The solid will absorb thermal energy from warmer vapour and unless it is very smooth it will provide nucleation sites.

0

By using a Resonance Tube. :) This is obviously the laboratory version of the experiment, but with a large enough tube, it can be done in a lake, too! Each frequency needs a different resonating length. You can even try this at home; buy a small speaker which emits a certain frequency tone, submerge a pipe into water - like in the picture - and slowly ...

6

The real issue is that the cup wasn't really full so that adding anything more would make it spill. You can clearly see the the level slowly growing above the top of the cup, as would be expected due to surface tension. Eventually another coin finally exceeded the limit, and a little water spilled. There is really nothing extraordinary going on here. ...

0

Edit: regarding your core question: no, if you drop a coin into a glass filled 'more' than the brim-level, such that any more water will cause it to spill, water will spill out. But, instead of a coin, if you insert something that has other properties that allow it to absorb water whilst not suffering any volumetric changes and has strong cohesive force ...

1

The generation of waves by wind is still an open question. Jeffrey's (1925) made a prediction based on wave shadowing, that is, he proposed that wind over waves would lead to higher pressure over the troughs and lower pressure over the crests, leading to wave growth. It turns out the theoretical growth rates for waves, based on this mechanism, are much too ...

0

The shadows that we can see with our naked eyes are simply areas less lightened than adjacent areas. If you are talking about the wet sensation this is determinate by the contact of several liquid (not all mercury doesn't wet you..) with your skin. When you touch water or a water wetted material part of the water molecules are transfer to your hands (an ...

5

Um.... a shadow is just an area where light doesn't reach, it isn't really made of anything, unless we go down to the light level, in which case wet doesn't mean anything. So the question really is meaningless, but if I had to answer, I would say no, shadows underwater are not wet.

2

There are a couple of reasons: the surface properties of the ice, and the formation of a thin layer of liquid water. First, ice tends to have a relatively smooth surface, due to the interaction of water molecules forming a regular, crystalline structure (that's what ice is, after all). Gravity helps: it pulls the surface molecules down, so they all tend to ...

3

All the ice we see around us in nature is not far off from the melting point of the ice - this gives a reasonable probability that there will be monolayers of water on top of the ice surface. Additional energy input by friction would cause more ice to melt on the surface, thus giving it a slippery property. Ice near absolute zero temperature (i.e. much below ...

1

A meltdown is unlikely from either of those alone, but if there is damage to the control mechanisms - the control rods and the cooling systems - then it does become possible. Say it sinks due to a malfunction of, say, the ballast system. Then the crew would have time to insert the control rods in between the fuel rods in the reactor. This means that each ...

1

The word meltdown isn't strictly defined and can cover a range of sins from the core melting into a blob and down into the ground (as happened at Chernobyl) through to fuel elements melting (as happened at Fukushima). At least two Russian submarines have experienced meltdowns, see here and here, though this was while they were floating not when they were ...

-3

Ice is the solid form of water. Under pressure, depending on the local temp and how much pressure is applies, ice changes state into liquid water. The more resistance a surface offers to objects moving across it, the less slippery it is. Say you put on ice skates, and skate. the blades exert enough pressure to melt the ice beneath the skates to form water, ...

1

In an ideal gas where P is the absolute pressure of the gas, V is the volume of the gas, n is the amount of substance of gas (measured in moles), T is the absolute temperature of the gas and R is the ideal, or universal, gas constant. The capped gas in the bottle cools, according to the black body radiation law everything cools at a certain rate. ...

38

Apparently this is a simple question with a not-so-simple answer. I believe the general consensus is that there is a thin layer of liquid water on the surface of the ice. This thin layer and the solid ice below it are responsible for the slipperiness of ice; the water easily moves on the ice. (Well, why is that? Perhaps another SE question.) However, this ...

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