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Questions tagged [density]

Density is defined as the mass per unit volume of a substance.

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Cosmology - Demonstration for equation of the evolution of the density contrast

In a context of cosmology, I need help about a differential equation that I can't get to demonstrate: The growth of density fluctuations obeys a second order differential equation. At early enough ...
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Can density replace buoyancy?

Recently I discussed the possibility of a flat earth, with a flat earther whom rejected much of established science, especially newton and his laws because Newton's idea of gravity rendered a flat ...
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Is there a limit to the amount of mass we can concentrate in a region of space?

Black holes are solutions to Einstein's Field Equations. Black holes contain a singularity hidden from the outer universe. As I understand, these singularities are infinitesimal and contain a very ...
34 views

What are typical atomic densities of solids and gases? [closed]

What are average values for the number of atoms per cubic cm for typical solids and gasses at atmospheric pressure?
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volumetric density from linear densities in the three directions x,y,z

I have a cube and I know the linear density of particles along each axis (I mean- the number of particles per unit length along each axis). How can I get the volumetric density?
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How is water heavier than petrol, even though its molecular weight is less than petrol?

Molecular weight of petrol is so much higher than water, but when it comes to physical property, weight, one litre of water weighs more than one litre of petrol. How is it possible?
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Why does a helium balloon rise? [duplicate]

This may be silly question, but why does a helium ballon rise? I know it rises because helium is less dense than air. But what about the material of the ballon. It is made up of rubber/latex which is ...
112 views

Does a non-buoyant (denser than water) object (such as a lead diving weight) weigh any less when submerged in water?

I've just been discussing this question with my eldest son, who is an extremely intelligent man, as well as being an engineer, a sailor and a scuba-diver, and he believes that an object heavier than ...
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Does optical density depend upon concentration of a solution?

Does optical density vary upon the amount of salts dissolved in water?
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Does the density of an object play a role for it's gravitational effects?

My thought experiment: We repalce our sun with an object of identical mass, rotation, shape, etc. but not the same density, i.e. the object would have a radius of 100km. The "replacement-time" would ...
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What does Earth feel like when squeezed?

he average density is about 4g/cm^3 so if the earth was in the size of an orange, it would feel like a rather heavy ball. The crust is relatively thin, and the earth is said to be solid land masses ...
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Negative probability distribution function for Dirac equation

People say that the probability density function of the continuity equation for the Dirac equation is definite positive. I wanted to see it myself and followed the same path as Bjorken & Drell's ...
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How do we know that dark matter energy density scales as $\rho\propto a^{-3}$?

How do we know that dark matter energy density scales as $\rho\propto a^{-3}$?
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Is the universe be expanding at different rates depending on its temperature and density?

As I understand it, when observing different regions of the universe we get a different rate of expansion (the two Hubble constants), specifically the more distant observation seems to return a lower ...
114 views

Black hole gravity and light [duplicate]

When an object is squeezed to its Schwarzschild radius it becomes a black hole (made by density) and its mass does not change (its gravity doesn’t change), but if its mass doesn’t change (its gravity ...
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Phase diagram of a fluid

How is it look like the phase diagram of a fluid in density-pressure plane? I came across the phase diagram in Pressure-temperature plane most of the time. But I can't find the phase diagram in ...
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Prove electric field is continuous at an external point $P$

I have a continuous charge distribution with density $\rho$. Can anyone please tell how shall I prove the electric field is continuous at an external point $P$? \$\displaystyle \mathbf{E}=\dfrac{1}{...
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Is it possible to have mass with zero volume?

As we had always studied that matter occupied space and has mass and our universe is made of matter so do that mean that there is no case where mass is present without volume .
Supposing a spatially flat, matter-dominated universe, the expression for the Hubble parameter is: $$H^{2}=H_{0}^{2}\left(\frac{\Omega_{m}}{a^{3}}+\Omega_{\Lambda}\right)$$ The previous equation ...