Density Definition and 1000 Threads

A receptacle has a mass of 3 kg when it is empty, 53 kg when it is filled with water, and 66 kg when it is filled with glycerin. Calculate the relative density of glycerine. I know the formula to find out the relative density. d= absolute density / reference density ( 1000kg/m3)

All, I am wanting to see why charge density divided by e nought is equal to F/q and V/d. Unit cancellation makes it easy to equate F/q = V/d, but why is charge density alone enough to be equal to the electric field? I feel like something is missing here but I can't reconcile it nicely in my...

Homework Statement What is the diameter of a copper sphere that has the same mass as a 9.00 cm× 9.00 cm× 9.00 cm cube of aluminum? Density of Aluminum = P(al) = 2.70g/cm3 Density of Copper = P(cu) = 8.96 g/cm3 Volume of Aluminum Cube = Vcube = 729 cm3 Homework Equations Volume of a Sphere =...

Hello! I am new to this forum, but I'll give it a shot. It is my understanding that photons have no mass- but that light is still pulled by the gravity of a black hole. How can something without a mass, and therefore, gravity, be pulled by the gravity of another object? Any insight would be...

There is something that I don't quite understand or want clarification. See John Wheeler article "100 years of the quantum" http://arxiv.org/pdf/quant-ph/0101077v1.pdf refer to page 6 with parts of the quotes read "so if we could measure whether the card was in the alpha or beta-states, we...

In another thread https://www.physicsforums.com/threads/why-does-the-universe-have-no-net-charge.843865/page-2#post-5326092 I was amazed to learn the following from a post by bcrowell: "You can't get the total mass of the system by adding up the masses of all its parts." The reason for this is...

Homework Statement A column of water 40 cm high supports a 30 cm column of an unknown liquid.What is the density of the liquid? Homework EquationsThe Attempt at a Solution As per the instruction of the teacher I equated their pressures. h1ρ1g=h2ρ2g. And hence arrived at the...

Hello Lastly I was thinking a lot about electron density definition. It is not intuitive for me and I'm looking for any mathematical tool that could explain it to me more. My friend told me about idea to derivate it from propability density function using Dirac delta distribution. I'd like to...

Homework Statement 1.0 mA proton beam accelerated through potential difference of 1 keV. Determine the volume charge density of the beam after acceleration assuming uniform current distribution within diameter of 5mm, with zero current outside of this. Particle starting from rest. Final answer...

Homework Statement A two-dimensional circular region of radius a has a gas of particles with uniform density all traveling at the same speed but with random directions. The wall of the chamber is suddenly taken away and the probability density of the gas cloud subsequently satisfies $$...

I asked this once before, but forgot the answer. I know the difference between the two. I would like to know why S.G. is even relevant since it seems to give the same answer as density. Ex. Density of a fluid is 10 g/cm3 and density of water at 4C is 1g/cm3 so the S.G. of the fluid is 10 (no...

Fermi's golden rule contains a term that is the density of the final states ##\rho(E_{final})##. For my problem we have no time depending potentials so that's the same as ##\rho(E_{initial})##. If I understand the definition of ##\rho## correctly, it's the number of states in an interval...

Dear all, I am trying to understand the physics behind the "number density" formula given by Weinberg. Is there anyone who can explain these parameters to me: 1- "Initial fluctuation strength": \begin{equation} \rho_1= \lim_{t \to 0}\frac{\Delta \rho_M^3}{\bar{\rho}^2_M}\end{equation} However...

Hi I'd like to ask you about interpretation of electron density definition. According to the "Handbook of Molecular Physics and Quantum Chemistry" it goes like: ##\rho (\textbf{r})=N \sum_{\sigma_1}^{\sigma_N} \idotsint_{\mathbb{R^3}} |\psi_V (\textbf{r}_1, \sigma_1;\dots...

First, we know for every wave function $$p(x)=\psi(x)^*\psi(x)$$ indicates the probability density of a particle appearing at the point x. So if we calculate $$P=\int _M p \text{d}x$$ this gives the probability of the particle appearing in the range M. On the other side, I was thinking about...

For a state |\Psi(t)\rangle = \sum_{k}c_k e^{-iE_kt/\hbar}|E_k\rangle , the density matrix elements in the energy basis are \rho_{ab}(t) = c_a c^*_be^{-it(E_a -E_b)/\hbar} How is it that in the long time limit, this reduces to \rho_{ab}(t) \approx |c_a|^2 \delta_{ab} ? Is there some...

Spacetime shrinks in a gravitational field. As I understand it, objects falling into a black hole will appear to contract in size and run slower as they approach the horizon. This is similar to how things contract and slow down when traveling close to the speed of light because they are...

I'm doing some research for a sci-fi story that I'm writing and hoping that some of you chemists can help me answer a quick question about the material of a hypothetical distant planet. If a distant planet were three times the size of Earth with the same gravitational pull, what would the...

Homework Statement Hi everyone. I watched a YouTube video earlier today which said that sound waves travel faster in more dense mediums. For example, sound travels faster in water than it does in air. However, on this webpage http://www.physicsclassroom.com/mmedia/waves/ltm.cfm it says that...

Homework Statement Determine ##P(X<Y|x>0)## Homework Equations X and Y are random variables with the joint density function $$ f_{XY}(x,y)= \begin{cases} 4|xy|,-y<x<y,0<y<1\\ 0,elsewhere \end{cases}$$ The marginal densities are given by $$ f_X(x)=2x\\ f_Y(y)=4y^3 $$ The Attempt at a Solution...

I searched for, but could not find any name or published value for a constant (with units m-3 K-3) which when multiplied by temperature (in degrees Kelvin) cubed gave the corresponding photon density (in m-3). Does anyone know of such a constant with a published value? I calculated a value, but...

Homework Statement I have a free Brownian particle and its coordinate is given as a function of time: And its first moment, or mean, is given as But what kind of probability density was used to calculate this first moment? Homework Equations I know that the first moment is calculated...

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eq.1 eq2. eq.3 eq.4Hello, I have a question about eq.4 If we find the closed surface flux integral of J, would it be current?

Homework Statement Not sure if this is the correct place to post so move if needed. In a cylindrical conductor of radius R, the current density is givne by j_0 e^{- \alpha r} \hat{k}. Where ##\alpha## and ##j_0## are some constants and ##\hat{k}## is the unit vector along the z-axis. ...

I always wondered this question i tried to ask my teachers but i keep forgetting so DOES the gravity of a planet determines its Density?

i have a mathematical question which is quite similar to one asked before, still a bit different https://www.physicsforums.com/threads/derivative-of-first-term-in-lagrangian-density-for-real-k-g-theory.781472/the first term of KG-Lagrangian is: \frac{1}{2}(\partial^{\mu} \phi)(\partial_{\mu}...

< Mentor Note -- Poster has been reminded that they need to use the HH Template and show their work >[/color] A distant alien world has an acceleration due to gravity of g=100 m/s^2. Beings on this planet float in an atmosphere with a density of 5 kg/m^3, and they have a mass of 1 kg. What is...

Homework Statement *This is not my whole problem, I am only stuck on how to interpret one part of the question. Put simply, I want to find the expression for the density of energy levels in a given energy band per unit volume (in some crystal structure). Say I have an infinitesimal interval of...

Hey, I've been searching around online, and I can't find anything on the individual densities of D2 an T3, only the mean density of all hydrogen isotopes. Thanks, NWFusor

Homework Statement I need to find the final impact speed of the flame of a non-uniform candle. I am given that the mass per unit length increases linearly from top to bottom starting with 1kg/m at the bottom and 10kg/m at the top. I need to find how fast the candle flame is moving once the...

Homework Statement A long, straight wire, radius R, carries total current I. The current is distributed in the wire so that the current density is proportional to s, the distance from the center of the wire. (a) Write an expression for the current density J in the wire, as a function of s...

Hi everyone, I am looking for a way to densify silicone oil. Foolishly, I tried to dissolve Calcium Chloride but as well all know, salt will not dissolve in oil. If anyone has any knowledge as to how I can increase the density of silicone oil I would greatly appreciate your input.

Hey there - I think I have an issue with my 3D density plots of the probability density of the Coulomb wave function. The reason I think something is going wrong is because my plots of |ψ(n=2, l=1, m=-1)|² and |ψ(2, 1, 1)|² are identical, while I would expect them to have the same shape but be...

Hi, I'm trying to make sense of a wave propagation problem. It's a 1D problem, modelling propagation of density perturbations which travel like waves in a fluid. The problem is governed by the mass and momentum equations and density is related to pressure using the bulk modulus of the fluid...

Hi, may I ask about this: In a normal orbiting system, if the orbiting object has the right velocity, it will stay in a stable orbit around the more massive one (to be precise, they will both orbit around their common center of mass, but for a galaxy this coincides with the galactic center)...

Hello, I'm a trainee teacher and I'm delivering a lesson with a practical where the students find the densities of various objects. I want to end the class with 8 to 10 true or false questions about density which test misconceptions on density. The one I have is Is a dense object always heavy...

Homework Statement There is an electrostatic potential, given by ## \phi(r)=\phi_0 e^{-\alpha r}## where ##\phi_0## and ##\alpha## are some constants. A: Find the electric charge denisty ##\rho(r)## which produces this aforementioned potential. A: What is the electric field...

A solid cylinder of uniform density of 0.85 g/cm3 floats in a glass of water tinted light blue by food coloring...

Homework Statement The problem I have is that we are asked to show the complex relative permittivity of a good conductor is erc = 1 + i(sigma)/(omega*epsilon_0) where sigma is the conductivity and omega is the frequency of an electromagnetic wave in the medium. This is fine, I calculated it...

Would the direction of the Magnetic Flux Density vector B at the south side be towards the south pole like this? and is the direction for B correct for the other side? One more thing, how can magnetic flux density be a vector and have a direction when its sort of a density, I mean its over an...

Homework Statement In an atom: suppose one electron orbits the n proton nucleus at radius r . Find the magnetic energy density, in J/m3, at the center of the atom due to the motion of this electron. NOTE: You can ignore the effect of other electrons in this atom. Homework Equations...

Homework Statement A bar suspended in air weighs 1.75 N The same bar weigs only 1.4 N when suspended in water. Calculate; a. upthrust b. density of the bar Homework Equations D = m/v F = m*a The Attempt at a Solution a[/B]. Upthrust is 1.75 N - 1.4 N = 0.35 N b. Assuming density of water...

Hi all, A question about the vacuum energy density and spectrum. The only spectrum that is frame invariant involves the cube of the frequency. Is it also possible to have a constant offset term (which would also be frame invariant), to 'adjust' the energy density so it doesn't turn out to be...

Homework Statement I am conducting some research and have come across a problem, it could very well be misunderstanding. I am trying to calculate electron density N.Homework Equations There was given a simple formula F = 9√N ... where F = critical frequency and N = electron density... But...

Hello folks, Can anyone explain to me what is the difference between magnetic field intensity H and magnetic field density B?

Homework Statement The center of a 1.00 km diameter spherical pocket of oil is 1.00 km beneath the Earth's surface. Estimate by what percentage g directly above the pocket of oil would differ from the expected value of g for a uniform Earth? Assume the density of oil is 8.0*10^2 (800) kg/m^3...

Homework Statement An 18 carat gold ring is made from an alloy containing 75% gold with small amounts of other metals including copper and silver. By considering the ring to be a cylinder, find an order of magnitude estimate for the mass of the ring. Homework Equations density of gold - 19.32g...

If the atmosphere was thiner would the sky be violet?, and if it was thicker would it be red?

Here's the question: http://imgur.com/N60qRmw I normalized the wave function and got A = sqrt(315/8L^9) but how would I plot representative snapshots if the exponential factor will cancel when I square it? It's not a mixed state so it shouldn't depend on time as far as I can tell. Should I use...