Questions tagged [density]

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

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1answer
592 views

How much vacuum is needed to lift?

Just like a balloon of Helium lifts about 1.02g for being less dense than the air. Does the same principle applies to vacuum being less dense than air? And if so, how much can a ballon (1L) of vacuum ...
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Is it physically possible to have and how dense is styrofoam with helium or hydrogen replacing the air or whatever gas fills the spaces in it?

Is it physically possible to have styrofoam with helium or hydrogen replacing the air or whatever gas fills the spaces in it? How dense would it be? Would it float on air? How much less dense than ...
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Atmosphere on Mars

I am currently building a simulation for the perseverance rover landing on Mars. I need to work out the atmospheric density / pressure at various heights. I looked at Wikipedia and the NASA website ...
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What's the name of this entropy based on particle density?

Say, at time $t$, the particle density in space is $\rho(\vec{x},t)$ and this distribution is normalized such that $\int d^3 \vec{x} \rho(\vec{x},t) = 1$. We can then associated a value similar to ...
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Proof that coefficients of potentials do not depend on surface density

I have trouble with a proof given on a wikipedia article (https://en.wikipedia.org/wiki/Coefficients_of_potential). Suppose we have $n$ ideal conductors embedded in vacuum space (with null ...
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In a mixture of two immiscible liquids, why does the denser liquid always settle down?

The same is not true for solids, e.g. an iron block kept over a wooden block.
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What would the graph of Density of the medium at $t=T/2$ vs $x$ look like?

... The displacement equation of a standing wave in a homogeneous elastic medium is given by: $y=acos(kx)cos(\omega t)$ where $k$ is the propogation constant( $=\frac{2\pi}{\lambda}$), a is the ...
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If dark energy creates space between stars and galaxies does this growing space compress all of them by a little factor?

If dark energy creates space between stars and galaxies does this growing space compress all of them by a little factor?So they lose some volume something like a baloon loses volume due to compression ...
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By how much does the gravitational redshift change a neutron star emission spectrum, thus disturbing the measurement of its surface temperature?

How much does the gravitational redshift change a neutron star emission spectra disturbing so the measurement of its surface temperature? I remember some tv-shows talking about Italian pasta when ...
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Density measurement with two components (one solid and one liquid)

Not sure if this is the right place, but here it goes. I wonder if this formula works for a mixture between a solid and a liquid: $$P_t = \frac{1}{\frac{X_a}{P_a} + \frac{X_b}{P_b}}$$ This in the ...
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What does $\rm kg m^{-2}$ mean in simple terms? [closed]

I'm reading a research paper on fish stocking density and they measure the density in terms of $\rm kg m^{-2}$ (i.e. stocking density is 1.27 $\rm kg m^{-2}$). I've googled it but still don't have a ...
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Find the density of the sphere, $\rho(r)$

If the field vector $\hat{g}$ is independent of the radial distance withing the sphere, find the function describing the density $\rho$ of the sphere, $\rho(r)$. In spherical coordinates, the ...
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Resulting slurry characteristics of mixing slurries of different densities in an overflowing reactor [closed]

Given a continuously overflowing reactor of $T \; hr$ residence time, a slurry of known varying flow-rate and varying density is introduced. How do we calculate the resulting density at outlet? I was ...
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Doubts related to speed of sound in different mediums

since childhood we have been taught that sound travels faster in solid (most dense) as compared to liquids (less dense). and speed of sound is greater in liquids as compared to gases (least dense), ...
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Relationship between gravity and density

So I have recently found that flat earthers believe gravity is not real and everything goes down because of densities, obviously, if this were true things would float up as our air is not very dense, ...
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Infering the mean distance from density

A simple calculation surely but how we can infer the mean distance $l_{\text{mean}}$ between particles from their density $n$, i.e : $$l_{\text{mean}}=\left(\dfrac{1}{n}\right)^{1/3}$$ ? I tried to ...
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How does density change with depth?

How does the density of water with constant temperature change with depth? Is this even possible to calculate? I know that density at the bottom is higher than at the top, but I am interested in ...
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State an equation for conservation of mass and use it to show that fluids of constant density are incompressible

I have the following question: State an equation for conservation of mass and use it to show that fluids of constant density are incompressible My solution (1): My solution (2): I don't know how ...
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1answer
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Distance between molecules in outer space

I read that space has a pressure of about $1.322*10^{-11}$. I am curious to know how far apart molecules are from each other because of this extremely low pressure.
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Is there a limit to the energy density of a battery?

Better battery technology is very important today: improving the energy stored per volume or mass. This led me to wonder whether there is a theoretical limit. (I'm not expecting that we are at all ...
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Got confused about weight loss in liquid [closed]

Suppose two objects of the same mass but of different densities are dropped on water. The large object (say polypropylene) has a lower density than water and the small one (say stainless steel) has a ...
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Negative mass density in cosmology?

I came across a problem in Chapter 6 of An Introduction to Modern Cosmology by Andrew Liddle that reads: Identify a sufficient and necessary condition that must be satisfied by the equation of state ...
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Why does carbon dioxide not sink in air if other dense gases do?

Why does carbon dioxide not sink in air if other dense gases do? We evidently do not suffocate by carbon dioxide sinking to the bottom of the atmosphere and displacing oxygen and yet there are gases ...
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Incompressible flow / The number of fluid elements per unit volume

If we have a steady isothermal incompressible flow (with non-zero velocity field), the density must be constant and uniform, right? so: Can we conclude that the number of fluid elements(fluid parcels/...
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Height variation with water inside a tube

I have quite a basic question in hydrostatics that's bugging me and would be happy to get some help. Suppose I have a tube inside a water tank (the tube's opening is inside the water) and say the ...
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Historical estimates of the density parameter

From the reference in this answer I learned that our current estimate for the density parameter (i.e., the density of the universe divided by the critical density, which determines the shape of the ...
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Can density be spatially dependent? [closed]

I was reading Gardiner's Handbook of stochastic Methods of Physics, Chemistry and Natural sciences. In page 4, he was discussing Brownian motion and referencing Einstein's own work on the subject. It ...
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Volumetric Dilatation Rate, Material derivatives, and Divergence

in class we derived the following relationship: $$\frac{1}{V}\frac{dV}{dt}= \nabla \cdot \vec{v}$$ This was derived though the analysis of linear deformation for a fluid-volume, where: $$dV = dV_x +...
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What affects Buoyant force?

Why isn't buoyancy affected by the object immersed in water? I know that more depth means more pressure means more buoyancy. But based on Newton 3rd law, the water should apply a force back on the ...
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What is apparent density?

For any floating body apparent weight and apparent density of body is zero.how.explain also explain what does apparent density meean.
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What density of an object of more than one substance affects the buoyant force?

If we immerse a sealed cup of a liquid in a fluid, what density is taken in consideration when it comes to the buoyant force, the density of the cup itself (the substance in contact with the fluid) or ...
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Tip of the Iceberg [closed]

Is it possible to approximate the volume of an entire iceberg if one happens to know the volume of the visible tip? (Assume the water is perfectly still.) If so, how may that be done?
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If cold air is denser then why is compression associated with atmospheric heating?

If cold air is denser than warm air then I would assume compression of air would cause air to cool and expansion would cause air to heat up. Why is it the opposite?
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What is the jerk parameter in terms of the Density parameters and equation of state?

In cosmology the deceleration parameter defined as the $$q_0 = \frac{1}{2}\sum_i\Omega_{i,0}(1+3w_i)$$ Is there a similar expression for the jerk parameter ($j_0$)?
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Why is SI-unit of density $\frac{\rm kg}{\rm m^3}$? [closed]

The CGS unit of Density is: $$\frac{\rm g}{\rm cm^3}$$ Then how can the SI or MKS unit of density be: $$\frac{\rm kg}{\rm m^3}$$ Shouldn't it be: $$\frac{\rm kg}{\rm dm^3}$$
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Why does air pressure decrease with altitude?

I am looking to find the reason: why air pressure decreases with altitude? Has it to do with the fact that gravitational force is less at higher altitude due to the greater distance between the masses?...
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3answers
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What do you mean by linear, surface and volume density?

For continuous mass distribution they introduce linear, surface and volume mass density (represented by $\lambda$, $\sigma$ and $\rho$ constants). I just want to know what they mean. Also, in books ...
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Seeking a plot of the energy history of the Universe

How can we plot the energy density $\rho$ as a function of the age $t$ of the universe (or temperature $T$) from the time of radiation domination to the time of cosmological constant domination with ...
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1answer
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How much does the radioactive core of a nuclear bomb shrink due to compression by conventional explosives before it goes critical?

I saw a claim online that the conventional explosions used to detonate a nuclear bomb "significantly" compress the radioactive core, but I can't find any numbers indicating by how much the ...
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1answer
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How to find the relative density of a solid soluble in water?

I know what is relative density and how to find it, but what I can't understand is how do I find relative density of something soluble in water like salt? Since, relative density is with respect to ...
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Fluid statics and and pressure

consider a fluid filled in a cylindrical container height $h$ and area of cross section $a$. The pressure at the bottom will be: $$p_0+\rho gh$$ but not $$p_0+\rho gh+\frac{mg}{a}$$ where $m$ is the ...
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Confused with a simple ideal gas model

For an ideal gas of two-component ($A+B$) mixture at a temperature $T$, which expression is correct? $$p_T=p_A+p_B \tag{1}$$ or $$\rho_T=\rho_A+\rho_B, \tag{2}$$ where $p_T$ and $\rho_T$ are the total ...
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Is there a reason behind why Archimedes principle works? [duplicate]

I think most of us are quite aware of Archimedes principle, but is there a reason to why it occurs? Is it just an observed property? Why is the upthrust equal to the weight of the liquid?
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What explains that volume of body submerged is indirectly proportional to the density of liquid? [closed]

I want to have a mathematical proof that explains why the volume of body submerged is indirectly proportional to the density of liquid it's submerged in. As a common example a ship sinks more in river ...
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1answer
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Reason for particular pattern of clouds near sun

In this picture it is clear that there is a larger no. Of clouds near the sun as compared to a distance farther. Moreover the clouds seem to form vortex rings around sun. why is there more density ...
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Does the density of ice increase further when it is further cooled?

As we know, water becomes ice at $0^°$C. After becoming ice, if we lower the temperature further ($<0^°$C), then does the density of ice increase further? If yes, in that case, does the volume ...
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How to pass to the densitized triad?

I am reading this paper A new phase for general relativity? by Bengtsson. How do you pass from equation (A11) to the densitized triad reported in eq (5)? If you calculate $E^a_i E^b_i=q^{ab}$ you ...
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Mass, density, and forces on a floating ball [closed]

If I have two balls, one completely in the water (mass = 4m), and the other half submerged (mass = m), the volume of both balls is V = 15 cm^3. They are tied together with a string. How can I ...
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1answer
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Definition of density of black holes

For a blackhole of mass $M$, radius $R$ and Schwarzschild radius $R^*$ (where $R<R^*$), its density $\rho$ is defined as $$\rho=\frac{M}{(R^*)^3}.$$ One reason I read for using the Schwarzschild ...
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Does air pressure have some effect on weight?

If one measure some object in air and then measure it in vacuum will there be any difference in weight?

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