# density's questions - Chinese 1answer

464 density questions.

### Density and refractive index of Water/sugar solution

I can't find a correlation or equation for refractive index of water and sugar solution of known density. Do you know where to find it?

### 1 Diamond ring around black hole

1 answers, 70 views black-holes speed-of-light density
I know that light takes longer to travel in a denser material, like diamond and I know that black holes also attract light. I was wandering what would happen if you would make a ring out of diamond, ...

### Measuring local properties in a suspension

0 answers, 7 views fluid-dynamics acoustics density
Considering a fluid with a certain known concentration of particles (eg: 40% per volume RBCs in blood plasma), how do I measure analytically the speed of sound in the medium and its density? i.e. ...

### Does the density of water affect the speed of sea waves?

2 answers, 27 views waves water speed density
In the case of light waves, the denser the matter, the more slowly they propagate. Do the water waves behave identically?

### -1 Neutron star matter density [duplicate]

1 answers, 61 views density states-of-matter
Edit: Replaced black hole with neutron star, thanks to safesphere for his comment. We're told that tiny volumes of matter have huge mass in a neutron star. For the sake of argument, if you had a 1cm ...

### 5 What atomic forces are acting to resist me pushing an air filled bottle underwater?

Yes air is less dense than water but how does the bottle know to rise or indeed to move? It's not electromagnetism I think. Does this have a relation to gravitational forces? Is it to do with the ...

### Finding density using bulk stress equation

Basically, I'm using the equation $\frac{F}{A} = -B\times \frac{\bigtriangleup V}{V_o}$. Originally I had to find the change in volume given an initial volume (B and pressure ($\frac{F}{A}$) were ...

### 9 Can you make a metal denser by melting it and make it cool down under high pressure?

The answer is probably no. But can you make a metal denser by melting it and make it cool down under high pressure? Or would it just crack under internal stress when it returns to a solid? I'm going ...

### 22 The Density of Clouds

Clouds are made up of tiny water or ice droplets, depending on temperature. This implies that cloud density is greater than that of dry air. Why don't clouds sink through their surrounding atmosphere ...

### 3 Hot air balloon - mass

2 answers, 671 views pressure density
Short background I'm aware that a hot air balloon rises up because of the less density than air. But I'm not sure about how that lower density is reached, and how it can be sustained over time. At ...

### How do I find out the net thrust produced by a propeller?

I am trying to find out the thrust that a propeller produces. Since a propeller can have various different types of inclination for it's blades as well as several parameters such as number of blades, ...

### Can I calculate the volume sputtering yield of a compound if I know the atomic component sputtering yields?

I'm running Monte Carlo simulations of a neon beam hitting a $\beta$-gallium oxide target. I set the initial bulk composition to be made of 40% gallium and 60% oxygen (Ga$_2$O$_3$). The simulations ...

### Can anyone explain centrifugation? [closed]

Why larger particles tend to remain at the bottom level of the test tube while the smaller particles form a layer above the larger particles?

### 1 How much air does it take to lift the seeds? [closed]

0 answers, 19 views pressure water air density
I have a vessel with seed and water in side. The is a total of 6100 Lbs. and water is 523.6 Gals. the bulk density of the seed is 178 Lbs/CuFt. The water seed mix is expected to be 8' above the ...

### Properties of singularity

I read that singularity is point in space where is infinite gravitational force caused by collapsing something very big into something very small. How can something with certain mass (star few ...

### 3 Relationship between electrical resistivity and density

I just read this answer on EE.SE and that triggered a doubt in me. If I were asked whether there is any relationship between the electrical resistivity and the density of a substance I'd answer ...

### 4 Does the definition of compressibility depend on the frame of reference?

According to many authors, a fluid is defined to be incompressible if the material derivative of the density $\frac{D\rho}{Dt}$ is zero, that is to say, that in an frame of reference following the ...

### 3 What is meant by incompressible flow?

What is meant by incompressible flow? The density of the fluid is a constant, $\rho = constant$ The density of a fluid has a spatial dependence but remains constant in time, $\rho = \rho(\mathbf{r})$ ...

### Definition of incompressible flow

What is the exact definition of an incompressible fluid flow ? Is it a flow with constant density OR Is it a flow with divergence free velocity field OR Is it a flow with Mach number less than 0.3? ...

### 8 Why does warm water sink?

It is well known that water at 4C is denser than water at 0C. This is the usual explanation for why a body of water freezes from the surface (also it's because ice is even less dense, but that's ...

### What is a black hole made of? [duplicate]

Since we know white dwarfs are made of electrons and neutrons stars are made of neutrons and quark gluon plasma. What can we say about the black hole in this sense since its properties are far ...

### 2 What kind of matter are black holes made of?

Imagine a black hole originally formed from, for example, Rubidium atoms. On the other hand, one made from, for example, Helium atoms. Will it be there any difference between the two? Or perhaps once ...

### -5 Applied physics to “fill the jar” problem [closed]

I think that the most of you are familiar with similar kind of problems / riddles: I always said that it depends upon the velocity with which the fluid comes out from the faucet. It doesn't seem ...

### 1 Is there a relation between density and gravity?

1 answers, 408 views gravity black-holes density
I often find this affirmation when scientifics reffer to black holes: "A black hole is so dense that even light cannot escape from it" Does this mean that there is a relationship between density and ...

### Calculating mass from the integration of the surface density of a disc

2 answers, 55 views mass density
If I had an equation for the surface density of a disc as a function of it's radius, such as: $$\Sigma = A\left(\frac{r}{B}\right)^{1/2}$$ where A and B are constants, and I want to find the mass, ...

### Why is Earth's gravitational pull only at its center?

Why is Earth's gravitational pull only at its center? Does acceleration due to gravity remain constant wherever I go in and on the Earth?

### -1 How does gravity affect density?

2 answers, 82 views gravity astrophysics density
In massive objects, gas can be compressed, raising the density of the celestial body. Does this mean that if I create 100 stars and planets, all with the same density and random sizes, some of those ...

### 2 Why is it said that density of nucleons in a nucleus is constant? [closed]

2 answers, 86 views nuclear-physics density
I can not understand how we came to this conclusion, i did not find a satisfactory explanation in the literature.

### 5 How does water pressure manifest itself on the molecular level?

2 answers, 960 views pressure water density
Second, related question: does water density relate to, or cause, water pressure? Everyone I talk to dismisses the idea that water density substantially affects pressure, and emphasizes that water is ...

### Black hole and particle law

0 answers, 29 views black-holes density
After neutron degeneracy pressure the becomes a black hole. Before the black hole forms is there is no matter capable of resisting the gravitational collapse? If after black hole is formed then all ...

### 1 What is the mass and density distribution of a Schwarzchild black hole in the viewpoint of distant observer?

According to Schwarzschild metric:  c^2~\mathrm d\tau^2 = \left(1-\frac{r_s}{r}\right)c^2 ~\mathrm dt^2 - \left(1-\frac{r_s}{r}\right)^{-1}~\mathrm dr^2 - r^2\left(\mathrm d\theta^2 + \sin^2\theta~...

### Effect of aeration on Celerity

0 answers, 35 views waves density oceanography
Suppose a ocean wave encountered a section of ocean which had a higher level of aeration from gas such as methane escaping from the seafloor. Due to the aerated sections apparent lower density would ...

### How to know wind speed, given the force

I'm doing a game that is set in a desert and there are sand storms that occur periodically. What I've done is very basic and far from realistic, which is ...

### 30 Why singularity in a black hole, and not just “very dense”?

Why does there have to be a singularity in a black hole, and not just a very dense lump of matter of finite size? If there's any such thing as granularity of space, couldn't the "singularity" be just ...

### How Can Somehing With Mass Have Zero Volume? [duplicate]

I am very under qualified when it comes to physics. So, please correct me if I asked a question that “can’t be asked”. With that being said, I ABSOLUTELY love astrophysics. Which is obviously ...