Density Definition and 1000 Threads

Hello Everyone, I have a problem which is flummoxing me concerning concrete! The density of concrete is approx. 2400 kg/m^3 (depending on mix) however the component parts which make up concrete are as follows: Water (density 998 kg/m^3) Cement (density 1506 kg/m^3) Aggregate...

Homework Statement The density of a cylinder is calculated from the following data: mass m= (9.1±1.1)g , diameter d = (2.8±0.2) cm , and height H= (4.1±0.6) cm. The error on the density, before rounding, is ( in g /cm3 ) Homework EquationsThe Attempt at a Solution

Homework Statement Note - I have used an image here. For the simple reason I don't want to confuse anyone by missing out subscripts. But if that is not acceptable let me know and I will attempt to write it out. Homework Equations I have considered using Poissons equation - but couldn't...

Homework Statement In deep water, it can be shown that ##\omega = \sqrt{gk/2}## Orcas (killer whales) have been filmed generating waves in deep water to knock seals off ice floes. Assume that an orca can generate a wavepacket which is simply half a sine wave (i.e. ##\sin(kx)## from ##kx =0##...

1) Alright, so the problem reads, "The liquid in a horizontal pipe of diameter d1 before a constriction is at pressure P1 and flowing with the speed v1, and then in the constriction with diameter d2 the gauge measures pressure P2. What is the density of the liquid?" 2) I'm assuming the...

I had this question : if a diameter of a string is increased , how will the linear mass density(u) value changes ? the answer was it will increase because mass will increase , but how the mass has increased ? so what other factors affect the linear mass density ?* μ=T/ λ2 f2

Homework Statement Homework Equations E= kq/(r^2), E*dA = Q/e0 The Attempt at a Solution Typically I understand how to interpret basic graphs such as going for V (potential) vs x graph to Electric field vs x graph by finding the slope of V since E= -grad V...and from their it's basic...

I am trying to calculate the density of energy states in a two dimensional box. The way my professor did this is by first calculating the amount of states with their energy less than some energy e and taking its derivative with respect to e. In order to see how many energy states there are with...

Kolb&Turner in "the early universe" mentioned that for a scalar field ##\phi## at finite temperature, ##p=-V_T(\phi)## and ##\rho=-p+T\frac{d p(T)}{d T}## where ##V_T## is potential energy including temperature correction. My question is: when we consider the evolution of the universe using...

I have difficulty in understanding the Density Operator. Please see attached file. (From the Book " Quantum Mechanics Demystified Page 250) Most grateful if someone could help! Peter Yu

I have a question about density: would it, in principle, be possible to create something with greater density and hardness than, say, Osmium? Or is that impossible? Is density constrained by the elements of the periodic table, or can something with greater density be created? The finished...

Homework Statement A river car ferry boat has a uniform cross sectional area in the region of the water line of 720m^2. If sixteen cars of average mass 1100kg are driven on board, find the extra depth to which the boat will sink into the water. Homework Equations Density= m/V Density= m/Area X...

Hi I began to study the basics of QED. Now I am studying Lagrangian and Hamiltonian densities of Dirac Equation. I'll call them L density and H density for convenience :)Anyway, the derivation of the H density from L density using Legendre transformation confuses me :( I thought because...

Hi, I am working on a project and came across a conceptual roadblock. I am working with a PSD, let's say the units are V^2/Hz. I choose a dF based on how many sine tones I want in the time signal I am going to create. I sample the PSD curve at my frequency bin locations; so I have both my...

Hi, i need to know the chemical formula of cement and resin and their densities. can someone help me, please? thank you in advance !

Homework Statement A swimming pool has dimensions 25 m x 10 m x 3m (length x width x height.) When it is filled with water, what is the force on the bottom (Fb) of the pool? On the long side (Fl)? On the short sides (Fw)? (note that integrals are required.) If you are concerned with whether or...

does the density of an object affect how fast it sinks? links to pages with more info would be great, thanks.

Homework Statement Homework Equations Ienclosed = ∫ JdA ∫B*ds = m0*I The Attempt at a Solution This is my take of finding [/B]when r is greater than R--so, the magnetic field is m0*I/2pir, since B(2pir) = m0*I This is because the amperian circle covers the whole wire. Can somebody verify...

I must be stupid but my textbook states that the refractive index of a media does not depend on the density according to the Lorentz-Lorenz formula (LL) (\frac{n^2-1}{n^2+2}) = \frac{4\pi Ne^2}{ 3m} \frac{1}{\omega_0^2 \omega^2} Specifically it (Physical Optics, Akhmanov Nikitin pp.367) says...

I need help guys I can't understand this Can anyone explain thoroughly how do I form the range for this question? f(x,y)= e-x for 0≤x≤y≤∞ 0 Otherwise Find P(x+y≤1) I attempted this by integrating through the range of 0≤y≤(1-x) and 0≤x≤∞ but that...

Today while reading a book i read that conductance of a metal depends on its density. But it is also dependent on its resistivity. Does that mean that resistivity and conductivity are proportional to each other?

Why does hot less dense air rise and cold more dense air sink? Also, why is hot air less dense than cold air?

Hello, I have a question regarding the density of the LHC vs. Cosmic Rays and why the big difference doesn't matter for particle research? As a reference we look at ultra-high-energy cosmic rays which are perfect for 'one on one' collisions, but isn't 'dosage' also a parameter to consider? --...

Hi all, I am trying to simulate ocean waves on a 3d grid of points. I have recently discovered the Pierson Moskowitz spectrum which will give a wave spectral density (ms/hz) for a given wind condition. I am trying to represent this by using a large number (say 64) Gerstner waves. Each wave I...

Why is milk with a higher relative density better than one with a lower one.

I'm taking a SS physics course and going through A&M and found something hard for me to understand. It is on page 44, starting with eqn 2.60. Another thread almost addressed my question, but I cannot post replies on the thread (click here). I think I understand what is going on in the 1st...

Homework Statement Homework Equations Density = mass / volume The Attempt at a Solution the correct ans given is B. Mass is constant. I calculated the volumes of each (the cube of the separation), found the difference in density and then divide the difference by the initial density. but the...

Hello, Homework Statement The joint probability density function of X and Y is given by f(x,y)=c*1(|y|<x<1) 1 is the indicator function -Find c -Find the marginal densities of X and Y -Find the means, variances and the covariance -Find conditional densities, means and variances of X given...

Is an exact solution to Einstein's Field Equations known for the interior of a sphere of uniform density (to approximate a star or planet, for example?)

Homework Statement [/B] Consider a spherical planet of uniform density ρ. The distance from the planet's center to its surface (i.e., the planet's radius) is Rp. An object is located a distance Rfrom the center of the planet, where R<Rp. (The object is located inside of the planet.) Find a...

I just have a quick question on which order around the numerator and denominator should be in the jacobian matrix that multiplies the expression. As in general Lecture Notes on General Relativity by Sean M. Carroll, 1997 he has the law as ## \xi_{\mu'_{1}\mu'_{2}...\mu'_{n}}=|\frac{\partial...

Hello! I know how to calculate band structure and density of states of photonic crystal (example is pic.1) Does anybody know how to plot such DOS maps? The second picture is from the article about photonic crystal fibers by Rodrigo Amezcua.

All we know that space creates particle pairs,virtual particles,they make a pressure and we call it casimir effect.I want to ask in universe Is there such a way to calculate How many particles created per volume per second.Or calculate energy density ? Thanks

Homework Statement Interstellar medium is composed of atomic hydrogen at 100 K and number density 2E-7 m-3. Compute the average thermal energy density of the milky way disk. Then find the average magnetic energy density given the magnetic field strength of 3E-10 T. Homework Equations E=3/2 kT...

Homework Statement In a particular region of the Earth's atmosphere, the electric field above the Earth's surface has been measured to be 148 N/C downward at an altitude of 260 m and 165 N/C downward at an altitude of 410 m. Calculate the volume charge density of the atmosphere, assuming it to...

According to my thermo textbook the density of states should really be called the density of orbitals because "it refers to the solutions of a one particle problem and not to the states of the N particle system". This makes perfect sense to me but now I'm confused about references to the density...

Hello, all. I have been working on the following problem and was wondering if someone could check my work and provide some valuable input: Here is my work: What do you guys think about my approach to this problem?

My reasoning: The magnetic force on charge q is Fm = qv x B B does not change |v|. Therefore, |Fm| is constant at time t > 0 and Fm is always perpendicular to the direction of movement of charge q. Fm behaves as a centripetal force, and thus the charge moves along the circumference of a...

Hi, I am studying Sean Carroll's "Lecture notes on General Relativity". In the second chapter he identifies the volume element d^nx on an n-dimensional manifold with dx^0\wedge\ldots\wedge dx^{n-1}. He then claims that this wedge product should be interpreted as a coordinate dependent object...

Homework Statement A dam is made which is rectangular and flat in profile. It is a depth of 25m and a width of 100m and holds back fresh water which has a density of 1000 kg m3 . What is the total force that the water exerts on the dam? Homework Equations F=ρA |dF|=pdA d/dz p=-ρg The Attempt...

Physical cosmology and astronomy, dark energy is an unknown form of energy which permeates all of space and tends toaccelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an...

Hi All, I'm working on a research project that requires putting an electrode array with 4 elements into a flexible tube filled with conductive liquid. The electrode array is a series of balls, with the first being positive and the last being negative. The idea is to measure the change in...

A 5.0 kg cube of metal has a density of 3000 kg m3 and is held by a vertical string while immersed in water which has a density of 1000 kg m3 . Assume that the cube is oriented so that all the faces are either vertical or horizontal. 1. What is the difference in pressure between the top of the...

An object has a density of 1250 kg m3 at 10◦C and a coefficient of linear expansion of α = 2.5 × 10−5 1 /K . What is the object’s density when the temperature is 25◦C? I have tried using the equation ΔL=αL° ΔT but this equation has nothing to do with density. the answer should be: 1248.6 Your...

Hi. Look at the picture on 1:28 and 1:37 in this video: How is it possible that the fermi-level is between two energy bands? The fermi level is defined as the highest energy level that contains an electron 50% of the time, so how is it possible for the fermi level being in an area that is...

I've got a homework question that I'm particularly stuck on: Suppose that the halo, assumed spherical, of non-baryonic dark matter surrounding our galaxy has mass ~ 5 x10^12 M solar and radius 0.1 Mpc. What it its average density in Kg m-3? I think that I need to use the formula...

How can I calculate the planar density of the (0,-1,1,0) plane in HCP? (in terms of atomic radius r)

Homework Statement A solid metal rod with dimensions 5 x 2 x 1 is placed with one corner at the origin, such that 0≤x≤5, 0≤y≤2 and 0≤z≤1. The rods density is described by ρ(x) = (3x2 +10x) / 25 a) find the total mass of the rod b) find the x-coordinate of the centre of mass of the rod. Homework...

Homework Statement Given the Lagrangian density \Lambda = -\frac{1}{c}j^lA_l - \frac{1}{16 \pi} F^{lm}F_{lm} and the Euler-Lagrange equation for it \frac{\partial }{\partial x^k}\left ( \frac{\partial \Lambda}{\partial A_{i,k}} \right )- \frac{\partial \Lambda}{\partial A_{i}} =0...

When matter is crushed in a neutron star are the atoms of molecules closer and the electrons are the same distance from the nucleus, or is the electron cloud closer to the nucleus? If the latter, how is this possible if the orbits have to have fixed orbitals due to the standing waves of the...