# Tag Info

### Can ants walk on liquid mercury?

Needing any excuse to break away from the work I was doing, I immediately assumed the task of answering this question. Yes, ants can walk on mercury with no trouble at all. I bet it was even kind of ...
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### Do the weights of two liquids not add when mixed?

Of course, by common sense, if you put together two objects with masses $m_1$ and $m_2$, and nothing comes out, then you end up with mass $m_1 + m_2$. Weights are a little more complicated because ...
• 102k
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### Why does a floating object displace more substance than a sunk object?

When submerged, the coin displaces as much water as it has volume (logical). When floating on the box, the coin displaces as much water as corresponds to its weight. As metal has a higher density than ...
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### Given that ice is less dense than water, why doesn't it sit completely atop water (rather than slightly submerged)?

When put in water, an objects sinks to the point where the volume of water it displaces has the same weight as the object. Archimedes was the one who discovered this. When you put lead in water, the ...
• 10.9k
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### What is the energy source if a tall water tank is used to transfer floating objects upwards instead of cables with motors?

The work you need to do (to insert the log) against the pressure of the fluid at that depth is equal to the work done by the fluid to get the log up to the height you desire. If you consider a log ...
• 7,318
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### Can ants walk on liquid mercury?

Whether or not a small animal/insect can walk on a liquid is determined much more by surface tension than by density. To see why this is consider a dense liquid without any surface tension. You would ...
• 1,036
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### Why do rotten eggs float in water?

The domestic chicken's egg shell has about 7000 pores that allow the embryo to breathe. When an egg rots the yolk and surrounding materials decompose and they give off gasses which can pass through ...
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### Can a battleship float in a tiny amount of water?

Yes it floats. And it has displaced its "own weight of water" in the sense that if you had filled the container with water and only then lowered the ship into the container, nearly all that water ...
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### Is it correct to say that "WE" feel only 5/140 of the actual weight of brain as buoyancy acts on brain due to cerebrospinal fluid?

Try not to be too pedantic with the biologists. They have our medical health to worry about. What is most likely that they are really trying to convey but failed to precisely state, is that if the ...

### Given that ice is less dense than water, why doesn't it sit completely atop water (rather than slightly submerged)?

I like to answer by reinterpreting your question: if you expect the ice to be completely atop the water because ice is less dense than water (as indicated in your left image), then you would also ...
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### Will a penny ever stand still in the water at a certain depth?

The answer is no. Water, being a liquid, is nearly incompressible, meaning that the density changes very little with increasing pressure. In the very deep ocean, the pressure can approach $10^{8}$ ...
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### Why does a fluid push upward on a body fully or partially submerged in it?

The fluid does not really exert an upward force on a body. It exerts a force everywhere on the body normal to its surface. [Adapted from Hyperphysics] In a gravitational field, the pressure ...
• 8,910
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### Why do we need to apply more force to push a submerged object deeper?

The force required to push an object into water increases as the object submerges, i.e. as the amount of water the object displaces steadily increases. But I think if you do the experiment carefully ...
Accepted

### Why do we feel weightlessness in water but not on land?

This is less of a physics question and more of a neurophysiology question. Physically, as you have noted, both the proper acceleration (measured by an accelerometer) and the coordinate acceleration ...
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### Will a penny ever stand still in the water at a certain depth?

Yes, it will, but in a different way than one might imagine. In the Earth's oceans it is definitely impossible. From the phase diagram of water, one can see that assuming a constant temperature of 300 ...
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### Why do rotten eggs float in water?

It doesn't need to be rotten. When the egg is getting old, it evaporate water and looses mass while drying. Even if not rotten.
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### Do the weights of two liquids not add when mixed?

@knzhou supplied a good answer. I’m going to offer a couple of other interpretations. The first has nothing to do with the fact that you’re mixing liquids—it’s just that there are difficulties in ...
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### Given that ice is less dense than water, why doesn't it sit completely atop water (rather than slightly submerged)?

I think the real question you're asking here is: why do less-dense fluids completely stay above more dense fluids, whereas less-dense solids partly sink? If the ice covered the same area as the water ...
• 14.9k
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### Can a submerged object in a free falling fluid sink faster than falling?

I want to supplement Emilio's intuitive answer discussing what would happen with some thoughts as to why what you propose in your second part cannot happen. What kind of object could fall out of ...
• 56.1k
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### Does an object float more or less with more or less gravity?

The object would actually float exactly the same for both values of $g$. Let $V$ be the volume of the body, $d$ its relative density, and $V'$ be the volume inside water. Then for equilibrium of the ...

### Which weighs more in atmosphere, $1\,{\rm kg}$ of steel or $1\,{\rm kg}$ of feathers?

Feathers are made from keratin, with a density of about $1.3\ \mathrm{g/cm^3}$. The net volume displaced by a kilogram of feathers is then $751\ \mathrm{cm^3}$. Steel has a density of \$7.86\ \mathrm{g/...
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### Can a ship float in a (big) bathtub?

Yes a ship can float in a big bath tub with very little water. No you do not need as much water as the weight of the ship. In theory, you can use less than a cupful! Image from B5-2. How much water ...
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### Why does a helium balloon rise?

The buoyant force* depends on the volume of the object (or at least the volume of the object submerged in the fluid) and the density of the fluid that object is in, not necessarily/directly on the ...
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### Can a submerged object in a free falling fluid sink faster than falling?

The Equivalence Principle tells you that physics in free-fall is identical to physics in an inertial frame in the absence of gravity, in which case there is no buoyancy and any changes to the boundary ...
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### Why does a floating object displace more substance than a sunk object?

The coin is denser than water. When placed on the box, it will displace it's weight in water, which is more volume than the coin. When placed directly in the water it will sink to the bottom and ...

### Can a battleship float in a tiny amount of water?

Note that the water does not need to have been present - this calculation gives just the way to calculate the non water volume occupied by the floating object (that hence is unavailable for water). ...

### Why does a helium balloon rise?

The high-level explanation is "buoyancy". If you want to know the actual mechanism, it's that the pressure in a fluid increases with depth: the air pressure at the top of a balloon is slightly lower ...
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### Why do we feel weightlessness in water but not on land?

Do you feel weightless when floating on water? I don't. I feel that the water is carrying me. I can feel how gravity pulls me down while the buoyancy force holds be up. Just like my soft mattress is ...
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