Density Definition and 1000 Threads

Hi, If you had a sealed round bottomed flask on some lab scales and you recorded the mass and then you removed all the air with a vacuum pump and then found the mass of the flask again would the difference between the two readings really be an estimate of the mass of the gas in the flask? The...

This thing has been bugging me lately that can the constant mass density phenomenon of the universe may not be due to inflation? Can it be considered a consequence of the Casimir effect on the ( Supposed) boundaries of the universe?

Homework Statement Hello :) This is a last resort. I'm stuck on what to do to complete this lab report table. We are required to conduct an online simulation at this link: Buoyancy Online Simulation This is the document of the lab report I'm required to fill up (I'm stuck at part 2) Homework...

Stage II and stage IV can be used to determine as the volume of the water displaced is given. Now how should the density be calculated :D I know the formula for density $density=\frac{mass}{volume}$

Homework Statement Find the center of mass of an inverted cone of height 1.5 m, if the cone's density at the point (x, y) is ρ(y)=y2 kg/m. Homework Equations The formula given for this problem is rcm=1/M * ∫rdm, where M is total mass, r is position, and m is mass. The Attempt at a Solution...

The formula for the radiation pressure P in n-dimensional space for a given internal energy density u is ##\frac{u}{n}##. I would really appreciate it if someone could provide a link that gives a simple derivation of this formula for dummies like me.

Question: On the Moon, the force of gravity on an object is only about one-sixth of its value on Earth. Decide whether each of the following would give an accurate measurement of the mass if used on the Moon a) A beam balance like the one in the diagram at the top of the page b) A balance...

I was overlooking page 47 of "The Physics of the Manhattan Project" 2.2 Critical Mass: Diffusion Theory, and author Bruce Cameron Reed reported that: Can anyone explain how Bruce Cameron Reed got from (2.18) to (2.19) I tried plugging ## N(r,t) = N(r) N(t) ## into (2.18) to get (2.19), but it...

Homework Statement : [/B] The density of the Earth's atmosphere varies with altitude, and can be approximated by an exponential: ρ(h)=ρ0e^(-h/h0) where ρ0 = 1.3 kg/m3 (the approximate density at sea level) and h0 = 8.2 km (this is determined empirically). Calculate the mass of 15 km of the...

Homework Statement The magnetic flux density in the vicinity of a large air-cored electromagnet is determined by measuring the induced flow of charge in a small coil as the current in the electromagnet is switched on -- see the diagram below. Calculate the magnetic flux density at the...

Homework Statement [/B] Two long, coaxial metal cylinders are separated by a material of conductivity sigma and dielectric constant epsilon. The radius of the inner cylinder is a, the radius of outer cylinder is b, and the length of both is L. Suppose that the inner conductor is held at a...

I'm trying to learn some basic quantum mechanics, mostly from I a mathematical perspective. I am trying to understand this with quantum states as vectors in a Hilbert space, bipartite systems, the difference between superpositions and ensembles of states, and density matrices. And it is the two...

In Jackson, the following equations for the vector potential, magnetostatic force and torque are derived##\mathbf{m} = \frac{1}{{2}} \int \mathbf{x}' \times \mathbf{J}(\mathbf{x}') d^3 x'## ##\mathbf{A} = \frac{\mu_0}{4\pi} \frac{\mathbf{m} \times \mathbf{x}}{\left\lvert {\mathbf{x}}...

Homework Statement In the picture below it is asked that i calculate the resultant electric field if the linear charge density is known. Calculate the resultant electric field of a charged semicircle wire (positioned as in the picture) at some point M on the Z axis if the linear charge density...

Homework Statement Two identical wires R and S lie parallel in a horizontal plane, their axes being 0.10 m apart. A current of 10 A flows in R in the opposite direction to a current of 30 A in S. Neglecting the effect of the Earth's magnetic flux density calculate the magnitude and state the...

Homework Statement An electromagnetic wave propagates through a gas of N free electrons per unit volume. Neglecting damping, show that the index of refraction is given by n^2 = 1 - \frac{\omega_P^2}{\omega^2}, where the plasma frequency \omega_P = \sqrt{\frac{Ne^2}{\epsilon_0m_e}}.\quad(1)...

Homework Statement A long air-cored solenoid has two windings wound on top of each other. Each has N turns per metre and resistance R. Deduce expressions for the flux density at the centre of the selenoid when the windings are connected (a) in series, and (b) in parallel, to a battery of EMF E...

Homework Statement The electric dipole moment for the water molecule equals $$ p = 6.13 × 10−30 C · m $$ Suppose that in the glass of water all molecular dipoles could be made to point down. Calculate the resulting surface charge density at the upper water surfaceHomework Equations [/B] ## P...

Hello, I'm trying to understand how to calculate de probability of finding a system in a specific eigenstate using the density operator. In the book of Balian, Haar, Gregg I've found a good definition of it being the expectation value of the projector Pr in the orientation of the eingenstate...

Homework Statement Hi everybody! I'm preparing for an exam of electromagnetism, and I am struggling with the last question of this problem (hopefully the two first ones are correctly solved): Given potential: ##\phi(\vec{r}) = k \frac{q}{r} e^{-r/R}## with ##r=\sqrt{x^2 + y^2 + z^2}## and ##R...

Homework Statement A long wire (X) carrying a current of 30 A is placed parallel to, and 3.0 cm away from, a similar wire (Y) carrying a current of 6.0 A. What is the flux density midway between the wires: (a) when the currents are in the same direction, (b) when they are in opposite...

Homework Statement A function, ##f\left(x\right)=\left|a^{\frac{\sin \left(x\right)}{\ln \left(ax\right)}}-\frac{x}{a}\right|##, intersects with another function, ##g\left(x\right)=\left|\frac{sin(ln(\sqrt{x}-\sqrt{a}))}{x^2-a^2}\right|##, at point ##Q(b,f(b))## and point ##R(c,f(c))##. A...

I thought that insulators cannot be charged in the inside or the outside, so how can they have any charge density inside? I know that electric fields pass through a insulator, so is that why they can have charge density? I am currently reading about electric flux.

Consider two atoms of platinum, A and B, in a sample of platinum. Atom A lives deep within the sample, and atom B lives at the tip of a sharp protuberance at the surface. My understanding is that electrons in the sample will accumulate within a surface defect such as the tip of a sharp needle...

At this point I was given rho, sigma and landa to hold value of these three different kinds of density ρ = Charge/Volume -------------- Volume Density σ = Charge/Area ----------------- Area Density λ = Charge/Length ---------------- Length Density How do I know which type of density to use over...

I read that niobium metal has a Cooper-pair density of about 10^22 per cubic centimeter. However, when a current flows through a superconductor my understanding is that it all flows near the surface, beginning at the London penetration depth, which is a very small distance. So, let's say that...

So my question is, is there a relationship between the density of a medium you are traveling through and the maximum speed achieved for an object of constant mass and shape traveling with constant thrust in both mediums? for example if i knew that an object traveled 8 times faster in 1 medium...

1) If I vary charge densities, but keep current density constant, do I get any sort of electromagnetic wave? 2) If the answer to question 1 is no, then if I vary charge densities, but keep current density constant, could I conceivably have a two isolated "open circuit" current elements of...

I'm starting out on DFT right now. I'm an experimental Physics student, so I'm not very familiar with theories. Can you recommend any good textbooks or resources that I can utilize for my study?? Thanks in advance.

Hi, In an article on theoretical fluid dynamics I recently came across the following equation: $$M_i = \sqrt{g} \rho v_i$$ where ##M_i## denotes momentum density, ##v_i## velocity, ##\rho## the mass density and g is the determinant of the metric tensor. It is probably quite obvious, but I do...

My question is about system of infinite number of point like particles with gravitation interaction (classic Newtonian interactions). If the infinite system can be considered to be in equilibrium, uniform density, in 3D, did anyone analyzed this system with regard to propagation of density...

As I understand it, the Universe is red-shifted (emission spectra) from any point of reference looking outwards. The Universe is expanding, but is matter being created at the same rate ? Does this mean that the density of matter in space is decreasing ? (density = mass / volume). What does this...

Hello Forum, I am revisiting Archimedes principle and its important consequences. I am aware that a cube (homogeneous) made of iron will always sink in water regardless of its mass. If we changed the iron cube into a different shape (cone, cylinder, prism, parallelepiped, etc.), the object...

Quoted data for cis and trans 1,2 dichloroethenes shows cis has higher density but lower melting point than trans. How can this be explained? Packing arguments are clearly unable to rationalise these observations. Other 1,2 disubstituted ethenes show similar pattern. Thank you.

We are doing spectroscopy on some semiconductors covered by a layer of Aluminium. My professor says it might be a challenge for to see the valence band structure of the semiconductor because the metal has a high density of states at the fermi level. Does this make sense to you? Does a metal have...

Homework Statement Given a density matrix of three qubit pure state, how can I know after do some transformation, this state belong to what class?. Class I mean here, either separable state, biseparable, GHZ state or W state? I mean here what is the indicator to me classify it? It is the...

If not why does the event horizon grow as more matter falls in?

When one reduces the intensity of let's say, an incandescent bulb (by varying the resistance, as seen in many homes), which decreases more, the photon frequency (not related to wavelength, but the time interval between photon emissions) or the areal density of the photons? To what extent does...

Homework Statement A hollow sphere of inner radius 9.0 cm and outer radius 10.0 cm floats half submerged in a liquid of specific gravity 0.80. (a) Calculate the density of the material of which the sphere is made. (b) What would be the density of a liquid in which the hollow sphere would just...

Homework Statement A block hangs by a cord from a spring balance and is submerged in a liquid contained in a beaker. The beaker in turn rests on a kitchen scales. The mass of the beaker is 1 kg, the mass of the liquid is 1.5 kg. The spring balance read 2.5 kg and the kitchen scales reads 7.5...

Homework Statement Assume that the pressure p in a star with spherical symmetry is related to the density \rho by the (distinctly unrealistic) equation of state p= \tfrac12 k\rho^2, where k is a constant. Use the fluid equilibrium equation obtained in Problem 23 to find a relation between \rho...

Homework Statement It is known that the potencial is given as V = 80 ρ0.6 volts. Assuming free space conditions, find a) E, b) the volume charge density at ρ=0.5 m and c) the total charge lying withing the closed surface ρ=0.6, 0<z<1 Homework Equations E[/B]=-∇VThe Attempt at a Solution (this...

Homework Statement An experiment probes a coherent process and the receiver is coherent. The autocorrelation function and the spectral density function are estimated and transformaed into atmospheric parameters. See Table 1 below 1) Calculate the maximum velocity (in m/s) that may be...

Homework Statement Two large non-conducting plates of surface area A=.025m^2 carry equal but opposite charges Q = 75microC. What is the energy density of the electric field between the two plates. Homework Equations I wrote the equations on my attempt. This was a multiple choice problem...

I always has the impression that the density of the universe is infinite at the singularity because its just amount of stuff divided by volume and if the distance between stuff is 0 then the volume is 0. So divide by zero and you get infinity. But I have been told by others that dividing by zero...

Homework Statement A metal wire is given a ceramic coating to protect it against heat. The machine that applies the coating does not do so very uniformly. The wire is in the shape of the curve The density of the ceramic on the wire is Use a line integral to calculate the mass of the...

In the situation consisting of a steady current of 1A in an arbitrary closed path, what would the consequences be for the electric field if the drift velocity was non-uniform along the path due to non-uniform carrier density? This would be a case of a "uniform" 1 amp, but where the charge...

Hello! Let's consider again a system of atoms with only two permitted energy levels E_1 and E_2 > E_1. When electrons decay from E_2 level to E_1, they generate a photon of energy E_{21} = E_2 - E_1 = h \nu. The number of photons (per unit frequency, per unit volume) emitted by such a system in...

For a standard solenoid, I've found that B=μnI where μ = permeability of the core (4π×10^-7 for free space) n = number of coils I = current Firstly, is the permeability of soft iron 0.08, as I found? Primarily, however, I'm wanting to know if this still applies for a mutual induction apparatus...

In any simple carboxylic acid there are two oxygen atoms then i have a confusion that which oxygen has more negative charge on it or which one has the most electron density on it?