Questions tagged [density]

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

Filter by
Sorted by
Tagged with
0
votes
1answer
9 views

Charge distribution and electric field on a conductive sheet

I have a sheet of paper, clad with a half-circle shape of conductive material. The half circle is not filled to the center. The inner radius is about 8cm, and the outer radius about 12cm, not that the ...
-1
votes
0answers
41 views

Friedmann equation rewritten in order to be integrated to calculate the age of the universe [closed]

How to go from here: $$ H^2(t)=\frac{8\pi G}{3}\left[\rho(t)+\frac{\rho_{cr}-\rho_{0}}{a^2(t)}\right] $$ , where $$ \rho_{cr}=\frac{3H_0^2}{8\pi G} $$ to here: $$ dt=H_0^{-1}\frac{da}{a}\left[\...
1
vote
1answer
56 views

Why does the speed of sound decrease with increase in density?

In my book it's written that speed of sound will in increase with increase in density of the medium as molecules with get closer to each other, but after some browsing on internet I found out about ...
0
votes
2answers
21 views

Body submerged in two liquids

A container has 2 immiscible liquid of different densities. Suppose water on botton and kerosene oil on top. A body floats at the boundary of both such that it is partly in water and partly in the oil....
0
votes
0answers
25 views

Magnetic field energy in a coaxial cable

I came up with a conceptual problem when I was doing an exercise which involved calculating magnetic field energy in a coaxial cable. The cable consisted of one inner solid conducting cylinder ...
3
votes
2answers
66 views

Free Fall with Drag and Varying Air Density

I am trying to plot a graph in Excel describing a free fall of an iron sphere dropped from an altitude of 12 km, while taking into account the different levels of air density affecting the drag. The ...
0
votes
1answer
75 views

Water at temperature of 4° C [closed]

We know that the density of of water at $4°\rm C$ is maximum $1\rm\: g/cm³$. But how is it possible?? Suppose I have $1kg$ of water at $4°\rm C$ .So it's density is $1\rm\: g/cm³$. But what if the ...
0
votes
1answer
22 views

How is the buoyancy force applied when the denser liquid is higher than the less dense one?

Imagine we have to liquids with densities $\rho_2$ and $\rho_1$ and $\rho_2>\rho_1$. Suppose we pour $\rho_1$ into a container. And then we pour $\rho_2$ on it. As a rule, the denser liquid ($\...
0
votes
3answers
43 views

Why the liquids that are denser, place lower than those who have lower density?

can somebody explain Why the liquids that are denser, place lower than those who have a lower density from a macroscopic and microscopic point of view??
1
vote
3answers
122 views

Why is an event horizon dependent on density?

It’s frequently stated in Astronomy documentaries that you could replace the sun with a black hole of equivalent mass and the orbital mechanics will continue as normal. This works fine in dispelling ...
0
votes
1answer
23 views

Charge Density as a function of the Electric Field

A ball with radius $R$ has a non-uniform charge density $\rho(r)$. The electric field of the ball as a function of position $E(r)$ is known. How would you then find $\rho(r)$? I was thinking that, by ...
1
vote
1answer
42 views

Accurate method or instrument to measure density of shaving cream foam or whipped cream foam?

I am currently filling a "standard" stainless steel cup of known volume with foam and then I weigh it. Then I calculate density. This method is pretty messy and I have to be careful about how I fill ...
0
votes
1answer
26 views

Question About Buoyant Force and Weight of an Object

Looking at the relationship between buoyant force and the weight of an object, I found this explanation, which makes sense "If the buoyant force is greater than the object's weight, the object ...
3
votes
1answer
39 views

Why do all heavier gases in the atmosphere not settle down to the surface? [duplicate]

Some pollutants heavier than air that are released into the atmosphere include $\text{CO}_2,\text{SO}_2,\text{SO}_3,\text{NO}_2$ etc. Since these gases are heavier than air, Why do they not settle ...
0
votes
0answers
4 views

How to calculate thermobaric heating and decelleration when object go from space into atmosphere (2D)

I'm making 2D game where ship landing from space to planet. I want to add atmosphere to planets with gradient density depending on height. And I want to use this atmosphere for converting object speed ...
0
votes
1answer
21 views

Is it faster to get warmer in warm vapor or in warm liquid?

Is it faster to get warmer in warm water vapor or in warm water in liquid form?
0
votes
0answers
16 views

Would gases of different densities separate in a scuba cylinder?

In scuba diving, we use the following gases: Air - mostly made of N2 and O2 O2 He If I was to fill a cylinder at 230bar and leave it aside, would the gases start to separate at some point due to the ...
0
votes
2answers
42 views

How can we make a spherical shell uniformly charged?

Today, I was studying Newton's shell theorem (ellectrostatics). There we considered a spherical shell of uniform surface charge density. Then a question popped out in my mind: How can we make the ...
2
votes
0answers
74 views

Charge density of a point charge [duplicate]

Is it right to say that the charge density of a point charge is infinity? if I were to take a uniformly charged ball with radius R and take the limit $R\to 0$, won't I get an infinite charge density ...
1
vote
0answers
20 views

Finding the density of a liquid using archimedes principle [closed]

I'm practicing some physics problems and came across one that's essentially this. An an object of mass $m_o$ has apparent mass $m_o'$ when submerged in a particular liquid. Derive a formula to ...
0
votes
1answer
37 views

Solving the continuity equation for a given mass-density

Given a smooth and time-dependent mass density $\rho(t)>0$ which is spatially constant in 3-dimensional Euclidean space. Let's further assume the continuity equation $$\dot\rho+\text{div}(\vec{j})=...
2
votes
2answers
62 views

Indefinite integral of a density function

Suppose that $\rho(x)=\frac{dm}{dx}$ is the linear density of a rod. Can we find the mass at each point of the rod by integrating $\rho(x)$, so that:$$m(x)=\int\rho(x)dx.$$ Can we do the same with ...
1
vote
1answer
69 views

Deriving buoyant force from first principles [duplicate]

How can buoyant force be derived from most basic laws of fluids ? I can think of easy one. Consider such scheme of body floating deep in water : Where $dA$ is elementary downward directed surface ...
2
votes
1answer
39 views

Do denser objects generally move down towards the “centre” (where $F_g = 0$) of a gravitational field relative to a less dense object?

Background( What I think is happening for fluids) Hello, I am high school student currently investigating buoyancy. Consider a dense liquid such as honey added to a less dense liquid such as water. ...
1
vote
0answers
27 views

Generalised basis independent relationship between Von Neumann Entropy and Purity of a quantum state [duplicate]

I have been trying to find a generalized relationship between Von Neumann Entropy and Purity of a quantum state? In this post there is a discussion of a specific case for a qubit and a more general ...
1
vote
1answer
46 views

Root Density Law equation - maximum impact depth

I'm reading the article "Depleted-Uranium Weapons:the Whys and Wherefores" by André Gsponer. In it he gives an equation and calls it "Root Density Law", for the maximum penetration length $L_{max}$ of ...
2
votes
1answer
108 views

Lost volume data of water and isopropanol mixtures [closed]

WHO has two recipes for disinfecting, based on ethanol and isopropanol (IPA). They typically start with an alcohol volume and then top it off with the other ingredients to 10 litre. One of the recipes ...
1
vote
0answers
38 views

On the adiabatic theorem

In the Adiabatic theorem explanation on Wikipedia it says: Diabatic process: Rapidly changing conditions prevent the system from adapting its configuration during the process, hence the spatial ...
0
votes
1answer
21 views

Macroscopic averaging validity (e.g. density)

When dealing with macroscopic scales, it is common to introduce continuous functions (such as density) which model the behaviour of the underlying microscopic matter. However, I still can't understand ...
0
votes
0answers
82 views

Water density as a function of temperature

I would like to know if there is an expression or a correlation to calculate water (not gas or steam) at different temperatures. If possible both nonlinear and linear temperature calculation. I only ...
3
votes
1answer
192 views

Is the Feynman's path integral a density?

The Feynman-Kac path integral formula is used to solve parabolic equations related to stochastic processes. Considering the probabilistic expression, the solution is indeed not a density. However, ...
2
votes
2answers
85 views

What is the relation between density and average distance to nearest neighbour?

Let's say I have the density of an object: say, $1 \space \mathrm{obj} \space m^{-2}$. This could, for example, be the number of balls on a football field. If we assume the objects are uniformly ...
0
votes
2answers
33 views

${\rm CO}_2$ Pressure Vs Temperature in Supercritical Phase

Say we have a compressed gas cylinder half full of liquid CO2 under its own vapor pressure. Below 31C the pressure and temperature in the cylinder follows the saturation line. If you know the ...
1
vote
1answer
33 views

Can electromagnetic waves be effected by high SPL mechanical waves?

I know that electromagnetic waves like radio travel freely without a medium, even through the vacuum of space. But, I also know that physical structures like buildings, walls, bodies can filter and ...
4
votes
2answers
111 views

Hubble tension and density parameter

Hi I was reading about the Hubble tension. I know that the Planck Collaboration gives an actual value for the Hubble parameter as $H_{0}=64.3 kms^{-1}Mpc^{-1}$ and the group that measures $H_{0}$ with ...
1
vote
1answer
57 views

Interaction of neutrinos with matter

I am an undergraduate student working on a project on neutrino oscillations. I am currently trying to code the probability of neutrino oscillations in matter (MSW effect). I am using the following ...
0
votes
0answers
30 views

Why buoyant force equals weight of fluid displaced? [duplicate]

I know how formula of buoyant force come (upthrust=$V\rho g$).I also know its derivation. I can understand why buoyant force equals weight of fluid displaced according to this equation but that ...
1
vote
0answers
50 views

Im trying to prove that a star can be described by a polytrope by deriving the polytropic relation of $P\sim p^n$ from the stellar structure equations

Suppose that in a star, the only source of energy generation is radioactive decay, so the energy production per unit mass is constant and independent of density and temperature. Further suppose that ...
0
votes
0answers
56 views

Why doesn't the atmosphere separate according to density? [duplicate]

Why don't dense gas elements sink to the ground and dense gas elements drift to the sky? Why don't we have layers of oxygen, nitrogen, carbon dioxide, etc.
0
votes
1answer
47 views

Inconsistency regarding Archimedes' Principle [duplicate]

According to the Encyclopedia Britannica, "[...] any body completely or partially submerged in a fluid (gas or liquid) at rest is acted upon by an upward, or buoyant, force the magnitude of which is ...
0
votes
1answer
39 views

What is cosmological critical density?

I'm taking a first course in cosmology and I'm struggling to understand exactly what critical density is. I've been told "Critical density is the energy density of the universe that corresponds to the ...
13
votes
2answers
819 views

Can a Black Hole become a normal mass again?

It is well known how Black hole forms. But once it is formed are there any circumstances which can lead a black hole to becoming a normal mass again?
0
votes
0answers
50 views

Regularization of an integral

I really need to properly evaluate the following integral. \begin{equation}\label{1} \frac{1}{2}\int dx \, dy \,\frac{\rho(x)\rho(y)}{(x-y)^2} \end{equation} Where $\rho$ is some density function ...
0
votes
0answers
27 views

Black Hole Mass Density Ratio [duplicate]

(1) The density of water increases as one approaches the bottom of the sea. (2) The density of neutron stars also increases from crust to core. Black holes with greater mass have a larger radius and ...
0
votes
1answer
73 views

How we can apply Archimedes Principle to rescue an Elephant, who has fallen into a well?

Recently, an Elephant was rescued. The rescue team claimed to have used the Archimedes Principle. They said that they pumped water into the well that made the elephant to float and come to the surface....
0
votes
2answers
98 views

Reason for lower air pressure above an airplane wing

I am posing this question from the perspective of a novice. I read an article, from Scientific American, titled "No One Can Explain Why Planes Stay in the Air". The article explains how, while we ...
1
vote
0answers
9 views

The Effect of Dissolved Substance to Water Density Anomaly

I've read this post Density of Solid State Compounds. As we all know, dissolved substance change water freezing and boiling points. My question is, how a dissolved substance affect the density anomaly?...
1
vote
2answers
74 views

What happens when you put (pour) water on water with the same density? (Archimedes)

Suppose you have a glass of water, and you pour on it a volume V of water of the same density; if we consider the archimedes principle, what happens to the water that is poured? Does it float, sink, ...
1
vote
1answer
115 views

Materials intermediate in density between osmium and neutronium [closed]

The densest elements on Earth are metals. Osmium is the most dense. The densest matter in the Universe is Neutronium which is not an element but degenerate matter. If we put Osmium and Neutronium on ...
1
vote
1answer
44 views

Home experiment to measure specific gravity of liquids

The problem states: invent to a way to measure specific gravity of various liquids in assorted bottles given 1 test tube 1 small vial of mercury 1 pen 1 ruler 1 beaker of water (500 ml) I know this ...

1
2 3 4 5
14