Density Definition and 1000 Threads

Homework Statement Homework Equations 1) PV = nRT 2 )## P = ⅓ ρ<c^2> ## 3) KE ∝ T The Attempt at a Solution According to the second equation above, density is inversely proportional to root mean square speed at constant pressure, but the answer states that the root mean square speed depends...

Hi, I'm a noob when is comes to these kinds of measurements on a spectrum analyzer. Take for example two LDOs: 1. http://www.analog.com/media/en/technical-documentation/data-sheets/ADM7154.pdf 2. http://www.ti.com/lit/ds/symlink/lp5907.pdf (see figure 17) They claim...

Homework Statement A quarter disc of radius 3 cm lies in the first quadrant. The areal density is (1.2 g/cm3)x + (0.7 g/cm3)y. Determine the mass of this object. Homework Equations The Attempt at a Solution For my bounds: x: 0 to 3 y: 0 to Sqrt[3 - x^2] When I took this integral I got...

Homework Statement If a 5kg object floats in water (density=1000 kg/m3) with 20% of it's volume above the surface of the water, what is the volume of the object? Homework Equations Archimedes' Principle = the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or...

In my lectures and notes my professor keeps writing out density as lbs/ft3 and unit weight as lbs/ft3. For a material such as concrete it could have a density of 167 lbs/ft3 but a unit weight of 103 lbs/ft3. I am confused as to how these two values are different even though they have the exact...

I was just wondering how number density relates to probability density in general, within particle physics? Thank you!

energy. Consider a particle in a box of the form ##V(x)= \begin{cases}0 \; \; \; -L < x < 0\\ V_0 \; \; \; 0<x<L\\ \infty \; \; \; \text{ elsewhere}.\end{cases}## One can show that the probability density ##P(x) = \Psi^* \Psi## is greater in the region of lower kinetic energy (that is at higher...

Imagine a planet similar to Earth, but exposed to a completely different star. The star has the same mass and emits the same amount of photons as the sun, but it is a huge, extremely slender torus made of 1 mm diameter neon tubing. The planet is on the axis of the torus and at the same distance...

Homework Statement If the density of the half-ball x ^2 + y ^2 + z ^2 ≤ 4 ; z ≥ 0 is given by δ(x, y, z) = ( x^ 2 + y^ 2 + z ^2)^(1/2) find its mass. Homework Equations ∫∫F⋅ds ∫∫FoΦ(u,v)||Tu,Tv||dudv ∫∫FoΦ(u,v)⋅(Tu,Tv)dudvThe Attempt at a Solution For the last problem I was asked to find the...

Homework Statement Measure the density if air at normal atmospheric pressure. You can use the following equipment: One scale with an accuracy of 0.01g Two empty glas bottles (≈0,33 liter each) One big bowl with water One cork with a valve and a vacuumpump Homework Equations Not knowing how...

Homework Statement This is problem 3.4 from Prucell and Morin if you have the book. Homework Equations None The Attempt at a Solution Electric field inside a conducting sphere is zero. Let P be a point on one of its equatorial plane. The field along the plane is zero. So I know the charge...

My question is why there is -1/2 for ω meson?

Homework Statement estimate the density of chromium ions in ruby, assuming that the concentration of chromium in ruby is about 0.05% by weight. Homework Equations decay rate = 0.5x10^3 s^-1 answer: density N (sub T)= 1.6x10^19 cm^-3 The Attempt at a Solution density = mass/volume density of...

I am currently interested in a system, where I have a big box of charges for which the density goes to zero at the boundary. What I wanted to do is try to derive what charge density will minimize the total electrostatic energy in the box. Now a cubic box gave me some complicated so I switched...

Homework Statement A wooden cube is floating in a cup containing drinking water and an unidentified fluid.0.5 of the cube's volume is submerged in water and 0.4 of the cube volume is floating on the unidentified fluid find the density of the cube and the density of the unidentified...

Homework Statement I am trying to calculate the charge density in the first subband (n=1) of the quantum well of length L as shown in the below figure. here is the electron wave function for the first sub-band and its value (from relevant equation 1) is given as Ψ12(x) = 2/L*sin2(πx/L) from...

Homework Statement The electric flux density in free space produced by an oscillating electric charge placed at the origin is given by \vec{D}=\hat{r}\frac{10^{-9}}{4\pi r^2}cos(wt-\beta r), \ \ where \ \beta=w \sqrt{\mu_0 \epsilon_0} Find the time-average charge that produces this electric...

Hello, As I understand there is a problem in physics where point-like massive (or charged, etc.) particles would have infinite mass/energy (or charge, etc.) density. I'm curious how in the context of String Theory how we address the same problem? I have come to understand Strings as...

Homework Statement I am trying to calculate the ratio of the density of states factor, ##\rho(p)##, for the two decays: $$\pi^+\rightarrow e^++\nu_e~~$$ and $$\pi^+\rightarrow \mu^++\nu_{\mu}~~$$ Homework Equations ##\rho(p)~dp=\frac{V}{(2\pi\hbar)^3}p^2~dp~d\Omega## Which is the number...

Homework Statement Electric current of I amperes flows along the z-axis from (0, 0,-∞) to (0, 0, -a) and from there it spreads over a conducting sphere r = a in the -aθ direction, comes to the point (0; 0; a) and goes to (0, 0, ∞) again along the z-axis. What is the surface current density at...

I know that if I multiply e^3/2 (e= 1.602x10^-19) to the unit below I can change it to eV Can somebody help me I don't know why

Homework Statement How do I find the total charge from a material with a charge density given by \rho =10^{-9} \text{cos}\left ( \frac{z}{z_0}\right ) C/m^3 that exist between \frac{-\pi}{3}z_0<z<\frac{\pi}{3}z_0. Homework Equations None I can think of. The Attempt at a Solution Attempt #1...

Homework Statement Hi! I need to solve a continuity equation for electron density as a function of time in the E-region of Earth's atmosphere. I shall neglect vertical transport and that the ion production rate completely shuts off dusk. Homework Equations See below The Attempt at a...

Homework Statement how can the average density of the body equal to the density of fluid(2nd photo) ? the object is not completely submerged in the liquid , so the density of object should be lower , right ? Homework EquationsThe Attempt at a Solution

Homework Statement A block of wood measures 2.2m by 2.5m with depth 3.6m with weight 102KN. When placed in water, how far will it sink? g = 9.81 ms-2 density of water = 1000kg m-3 Homework EquationsThe Attempt at a Solution Volume = 2.2(2.5)(3.6) = 19.8m3 Mass = 102000 / 9.81 = 10398 kg...

I was having a discussion with a friend as to whether or not a planet of rocky composition could exist with an extremely high density. We were thinking something approximately Earth sized, but weighing 4.35 × 10^27 Kg. He says it's impossible, whereas I think it is. Any help anyone can provide...

So, I was wondering this; since fusion takes two atoms and combines them into one nucleus, can that increase the density of the resulting nucleus?

Homework Statement Hi! I wasn't sure how to ask this, but my team and I are making a manila file folder bridge and we are stuck a specific part. We are looking to get the mass of the members and we decided to get it through multiplying the volume of the member by the density of manila file...

I am trying to compute the density of argon given the following conditions: T = 7000 K P = 21331 Pa For typical gases, I do not believe the ideal gas law would hold for such a high temp&low pressure regime, but since Argon is largely non-reactive, do you guys think using the ideal gas law would...

Homework Statement (This is a long problem but I think the question is not hard.) Determining the star density from star counts is tough, but estimating counts from a density law is simpler. In practice, this method of fit-ting observed number counts to an assumed density law is becoming a...

Homework Statement Hi! I really need help with finding time- dependent continuity equation for electron densities in the atmosphere. I've tried to solve it without any success. My question is if someone can give me a good link/link or equations that I can start with. Homework Equations See...

Homework Statement [/B] Consider a long chain of mass m and length L suspended from a tall ceiling. Like any string if one end is disturbed waves will travel along the string. However, the tension in the string is due to its own weight and is not uniform. As such the speed of the wave will be...

Homework Statement Homework Equations See below The Attempt at a Solution \begin{align} \begin{split} p(x) = C \ x \ exp(-x/ \lambda) \end{split} \end{align} If $p(x)$ is a probability density function on the interval $ 0 \textless x \textless + \infty $ , then it follows...

Homework Statement I want to find the mathematical proof to show that the density of an object changes with thermal expansion. My professor showed this in class and it was horribly wrong because he let a few things out. The book I'm reading showed it in 4 steps and left out a lot of the crucial...

It is easy to show that when you have a quantum system, let's think for example in electrons in a metal, then there appears summation over electron states of the form, e.g. for the energy for a free electron gas at T=0K: ##E=2 \sum_{k\leq k_f} \frac{\hbar^2}{2m}k^2## Where ##k_f## denotes the...

Hello, I am new to the forum, so I am directly stating my questions. 1)What determines the density of states of Phonons in a semiconductor? 2)Does degeneracy of semiconductors depend only on doping? Thanks

Homework Statement in this notes , i was told that the PV=mRT , why ? shouldn't PV= NRT , N=number of moles ? it should be PV = m/M (RT) , right ? Homework EquationsThe Attempt at a Solution

Hi, I've been given a list of heights and corresponding densities of air at these heights. I'm trying to find an expression for the variation of density with height. From the data, it looks like the density would be equal to some kind of logarithmic relationship? However, I'm not too sure how to...

Homework Statement For the observation of quantum mechanical Bose-Einstein condensation, the interparticle distance in a gas of noninteracting atoms must be comparable to the de Broglie wavelength, or less. How high a particle density is needed to achieve these conditions if the atoms have mass...

Hi, I'm looking for a liquid that is nontoxic, high transmittance, has a specific gravity higher than 1.3. Here is the catch. I'm using it to separate resin, so it can not dissolve or react with resin. there was a similar topic on high density fluid on other forums, but I'm using it...

Homework Statement Consider the diffusion of a drop of ink in a water vase. The density of the ink is ## \rho (\vec{r}, t) ##, and the probability ##P(\vec{r}, t)## obeys the diffusion equation. What is the relationship between ##\rho (\vec{r}, t)## and ##P(\vec{r}, t)##? Homework...

How do you go about calculating electron densities, especially when impurities are involved?

Five days ago, I filled a glass 2L bottle about halfway with litchis, then filled the bottle with water till the end and sealed it with its cap. I was curious to see how it decomposes in there. This morning, about 1/7th of the water was lying in a puddle around the bottle. I could see gas...

I usually come across expressions for the Stress energy tensor showing them as three densities (normally over a space-like slice. In wikipedia's article on the spin tensor, they clearly (it does not appear to be an error) both write about and express the components of the stress energy tensor as...

Homework Statement We fully submerge an irregular 3 kg lump of material in a certain fluid. The fluid that would have been in the space now occupied by the lump has a mass of 2 kg. a) When we release the lump, does it move upward, downward, or remain in place? b) If we next fully submerge it in...

I observe that electric arc forms a curve. I think that this is because electric arc is extremely hot and hot air goes up because it has less density. So if electric arc occur at 0 gravity would it be straight? from wikipedia https://en.wikipedia.org/wiki/Electric_arc Thank you.

Homework Statement If you have a body that weighs 100 N dipped in oil that has density equal to 0.8 g / cm³. This same body when immersed in water begins to weigh 60 N. How do I find the density / specific body mass? Homework Equations Solution= 1,3 g/cm³ The Attempt at a Solution Already...

Is it possible to work out analytically how the mass density profile ρ(r) of a ball of gas (spherically symmetric) evolve with time given the initial profile ρ0(r)? The assumption here is that the particles collapse only under the influence of gravity. I thought of this question in the process...

Homework Statement I am trying to solve Problem 2.45 in Electrodynamics by Griffiths, however, my answers were different from those in the book, I am suspect I got a missing step but I could not find it, so here is the Given Problem Find the charge density \rho given by a potential...

How does insulator's density affect its thermal conductivity? For example, considering such insulators as rock wool, It seems that the thermal conductivity should increase with an increase in density (due to elimination of 'air pockets'). However, experimental results, in many cases, look more...