All Questions

0
votes
0answers
10 views

Spin-orbit interaction for titanium in the excited state $(3d)^1(4p)^1$

Let's look at a Ti-atom in an excited state with 2 valence electrons $(3d)^1(4p)^1$. What term schemes $^{2S+1}L_J$ do we have for this state considering spin-orbit interaction? My take: For both ...
0
votes
1answer
36 views

General formula for the variation of the chemical potential with temperature

For small temperatures $T$, such that $k_BT\ll \mu(T=0)\equiv \mu(0)$, the variation of chemical potential with temperature is given by $$\mu(T)=\mu(0)\Big[1-\frac{\pi^2}{12}\Big(\frac{k_BT}{\mu(0)}\...
0
votes
2answers
54 views

mechanics: angular momentum of disk

I am studying mechanical engineering and I've got a problem with the angular momentum of objects that have a rotation which is rather complex to describe like the following: The shaft rotates around ...
1
vote
2answers
29 views

Can't see any traces of particles in my Wilson chamber without radioactive material

I am doing an essay about particle physics and I need some help. I am comparing the results in a Wilsonchamber with and without a radioactive material present. I were able to see a lot of traces from ...
1
vote
0answers
31 views

When and how was the need for symmetry in the stress-energy tensor first realized

This question is somewhat historic. Let $\Theta_{\mu\nu}$ denote the canonical stress-energy tensor of some matter field $\psi$ in special relativity. It is often stated that the reason why we want ...
0
votes
0answers
22 views

Stephan Boltzmann law

I was preparing for INAO when I came across the application of Stephan Boltzmann law...it's says that energy absorbed per unit time by a planet is Flux times πr^2. But why did we multiply with πr^2 or ...
-3
votes
0answers
37 views

Regarding change in kinetic energy [on hold]

When does change in kinetic energy equals zero? Also, is the initial velocity is zero for all the bodies ? Please explain.
2
votes
1answer
28 views

Meaning of ft-values in nuclear physics

What is the "physical" meaning of the ft-value for a decay channel? From what I understand, the ft-value is inversely proportional to the square of the matrix element, hence I would expect a larger ft-...
0
votes
1answer
43 views

Reflection Vector (Ray Tracing)

Snell's law of refraction at the interface between 2 isotropic media is given by the equation: \begin{align} \tag{1} n_1 \,\text{sin} \,\theta_1 = n_2 \, \text{sin}\,\theta_2 \end{align} $\qquad$ ...
1
vote
1answer
36 views

Real gas heat calculation [on hold]

For the Van der Waals gas we get a cycle consisting of 2 isobaric and 2 isenthalpic processes. The state equations are given as: $p = \frac {RT}{v-b} - \frac {a}{v^2}$ $\;$ and $\;$ $u = cRT ...
0
votes
0answers
24 views

Electrodynamics of inhomogeneous media

I'm interested in electromagnetic scattering and for that purpose I would like to write out Maxwell's equations for space-dependent permittivity (and permeability). Actually I only need them for ...
-8
votes
0answers
45 views

Ok. I'll try again [on hold]

A Hypothesis. In the Electromagnetic Donut variety of Fusion Reactors.. Using the EM Fields to bring the Plasma To but not pass the Fusion Threshold. A portion of the Plasma is brought passed it by ...
0
votes
3answers
66 views

Difference between center of mass and center of gravity

Let's consider a very tall building (g would be variable) which is rotating with the earth naturally. Now do the centrifugal force and the gravitational force act on the same spot? If not why does the ...
0
votes
1answer
17 views

Rotational dynamics regarding uniform rod

Is centripetal force present in rotating objects? I just solved a question in which an uniform rod rotates about a vertical axis with its one end pivoted. The angular acceleration is found by just ...
2
votes
1answer
47 views

Differentiating Scalar along a geodesic

I have been studying GR for sometime and doing exercises from Schutz and I have a question about differentiating along a geodesic. Here is what I know. The equation of geodesic in terms of four ...
2
votes
0answers
31 views

Equivalence between Maxwell's equations and vector Helmholtz equations

When are equivalent the Maxwell's harmonic equations: $$ \nabla\times\left(\nabla\times\mathbf{E}\right)=\mu\epsilon\omega^2\mathbf{E} $$ and the vector Helmholtz equations: $$ \nabla^2\mathbf{E}=\mu\...
1
vote
1answer
36 views

Newtonian Mechanics cannot be applied in non-inertial frame of reference then how can we apply formula for normal force in an accelerating elevator?

In my physics book there is a diagram in which a block is placed on a table. The table is exerting an upward force $ F_n $ (normal force) on the block and there is a downward force $ F_g $ (...
0
votes
2answers
52 views

Time for black body to cool to a given temperature

I'm trying to figure out the time required for a blackbody to cool assuming it only looses heat via radiation. I can estimate the mass, specific heat, surface area, emissivity, initial temperature, ...
14
votes
5answers
10k views

Why doesn't the Earth accelerate towards us?

According to Newton's third law of motion that states that every action has an equal and opposite reaction. So, if the Earth exerts a gravitational pull on us (people) then even we should exert a ...
0
votes
0answers
13 views

2D BHZ tight binding model for Quantum spin Hall insulator

I am currently reading this article : https://arxiv.org/abs/cond-mat/0611341 and want to derive the k-space tight binding model of 2D BHZ. The tight binding model is written as \begin{equation} H = \...
0
votes
2answers
38 views

Is an inertial force needed to be added to second Newton's law when transforming from cartesian to cylindrical coordinates?

Let's consider I have a particle moving on the $x,y$ plane. On this particle acts the Lorentz force, however it does not necessary perform a rotation by the axes origin $(x,y)=(0,0)$. I would like to ...
0
votes
0answers
15 views

What is the relationship between directions in reciprocal and real space of a photonic crystal?

I am reading "Photonic crystals - molding the flow of light" by Joannopoulos et al. (available on-line). The figures below are reproduced from there. This is a diagram of a triangular lattice of air ...
0
votes
0answers
15 views

Doubts with the formation of bullet cluster

The bullet cluster is formed by the collision of two clusters of galaxies. After the collision, the stars and galaxies in those two clusters passed through each other. But the intergalactic gas clouds ...
0
votes
1answer
24 views

AC circuit with resistor

As you can see from the image that "potential drop must be equal to the applied emf". This means after that point there is no flow of current as potential difference is zero.But how is this possible?...
-6
votes
1answer
35 views

SuperString theory and mass-energy equivalence [on hold]

Please ignore the previous question. As i had said that i knew that the energy released in electron-positron annihilation is 511keV in form of gama rays. Please reply- What is(or whether there is a) ...
1
vote
0answers
24 views

QCD gluon physical polarisation sum in the three gluon vertex

In the Compton scattering quark($p_1$) + gluon ($q_1$)-> quark($p_2$) + gluon($q_2$), there is three gluon vertex contribution. If we choose the physical polarisation sum $\sum_{\lambda} \epsilon^a(\...
0
votes
1answer
29 views

Projectile motion launched at an angle and landing higher than start [on hold]

If a projectile is launched from the floor, and lands at an elevated height how would one find the initial velocity given only (angle of launch, angle of ending elevation, total distance, and gravity?
0
votes
1answer
23 views

Why does certain clear plastic have an inner glow?

A type of plastic used in packaging for tamper resistant seals appears to have (what I can best describe as) a purplish inner glow under sunlight, and perhaps other bright light. In the image below, ...
0
votes
1answer
15 views

Problem on force components [on hold]

In this problem, is the direction of tension(725N) shown in the free body diagram correct? Wouldn't such a direction lead to compression instead of tension.
0
votes
0answers
15 views

Determination of Dead time of a Geiger Muller counter using the two source method

While determining the dead time of a GM counter using the two source method, why do we ensure that only two sources are placed in the counter at all times i.e. while determining the counts when both ...
1
vote
0answers
29 views

A unitary that induces Entanglement Breaking Channel for any ancillary state

Let's say there is a unitary operator $M:\mathcal{H}_1\otimes\mathcal{H}_2\to\mathcal{H}_A\otimes\mathcal{H}_B$ such that the channel $\Phi$ given as $$\Phi(\rho)=\text{Tr}_BM(\rho\otimes\phi)M^\...
0
votes
0answers
38 views

Maximum achievable mechanical work when heating water

I am doing a question about finding maximum achievable mechanical work when 1L of liquid water is heated from T₁ to T₂ at atmospheric pressure. The solution is $$W = \int_{T_1}^{T_2} \frac{T - T_1}{T} ...
-1
votes
0answers
12 views

Calculate velocity at a distance or time when accelaration is varying under gravity [on hold]

How to calculate velocity at a distance or in time of an object under varying acceleration ? e.g. object falling to earth from a height of 10,000 km ; say it starts at initial velocity 0, what is the ...
0
votes
0answers
18 views

If is work done by magnetic field is 0 then why does 2 magnets attract when kept together? [duplicate]

If 2 magnets are kept close to each other they attract then shouldn't it be considered as work done by magnetic field?
29
votes
5answers
7k views

Is the Higgs boson an elementary particle? If so, why does it decay?

The Higgs boson is an excitation of the Higgs field and is very massive and short lived. It also interacts with the Higgs field and thus is able to experience mass. My question is why if according to ...
0
votes
0answers
16 views

Pressure inside the elevator [on hold]

A barometer kept in an elevator reads 76 cm when the elevator is accelerating upwards. The most likely pressure inside the elevator (in cm of Hg) is (1) 74 (2) 75 (3) 76 (4) 77
1
vote
3answers
34 views

What are the factors on which wavelength of X-rays depends upon? [on hold]

So the thing is that I was learning about X-rays and I came across this line that minimum wavelength of continuous X-ray spectra depends only upon Anode voltage about which I'm sceptical because $$eV=...
1
vote
1answer
24 views

Quantum tunneling in a capacitor

Ampere's law of Maxwell's equation includes displacement current as the Maxwell's correction. Suppose consider a capacitor with a thin distance of separation. For an applied voltage do they posses ...
0
votes
2answers
44 views

Does potential energy get transferred from my body to a wall when I push a wall and fail to move it?

When I push a rock (and fail to move it), I do not do any work and therefore there should be no energy transfer. But my teacher says that, when one pushes a rock, energy is transferred to the rock ...
-1
votes
1answer
36 views

Kinematics lessons involving calculus [on hold]

Does solving instantaneous velocity involves calculus in kinematics? What are the other lessons or unknown variables in Kinematics that involves the use of Calculus? What are the other lessons also or ...
0
votes
0answers
14 views

Relationship between poynting vector and radiation pressure

I know that When an electromagnetic wave is absorbed or reflected by a surface, the momentum of the wave is transferred to the surface. I also know that for absorption the radiation pressure is 〈S〉/c ...
0
votes
1answer
33 views

How is the normal force on a banked track larger than gravity?

The formula of the vertical force of an object that is not accelerating up or down on a banked curve is: Ncos(θ) = mg There is also a centripetal force component which shows that the normal force is ...
2
votes
3answers
52 views

Explanation of Lenz's Law phenomena

If we drop a magnet through a copper pipe (without it touching any of the sides), it would fall slower than it would if there were no pipe. Having the pipe otherwise accelerate the magnet would be in ...
2
votes
1answer
36 views

Does polarized light reflect in the same polarization?

If vertically polarized light hits a linear polarizer aligned at a 45 degree angle from the polarization of the light, my understanding is 50% of the light will pass through and have its polarization ...
0
votes
0answers
43 views

Compactness and Quantization

So I was thinking today about when observables become "quantized", and came to the conclusion that every instance of quantization I've ever come across has come about from solving the Schrödinger ...
3
votes
2answers
71 views

Work extracted from a pressure cooker

How much work can you extract from a turbine connected to a pressure cooker? The situation is modeled as a rigid adiabatic tank of volume $V_{tank}$, which initially contains water at a high ...
0
votes
0answers
19 views

Flow generated by vortex near a rigid cylinder

I have a problem with complex potential and can't figure out how to approach it properly. The problem: Find flow around cylinder of radius $a$ generated by vortex of cicrculation $\Gamma$ at point $b$...
0
votes
0answers
20 views

Kirchoff's rule DC circuits [on hold]

I understand how to solve for the unknown variables but I have trouble labeling the currents and finding the current and junction equations
1
vote
1answer
69 views

Bosonic representation of $SU(N)$: what values can $n_b$ take?

In Assa Auerbach's book on page 166, he describes the construction of a bosonic representation of $SU(N)$ where the generators $S^{mn} \rightarrow b^\dagger_m b_n$. I'm a bit confused about the ...
-1
votes
0answers
16 views

Determine Fuel Flow for the piston engine [on hold]

A piston engine produces 400 kW of power. Its sfc is 75 μg/J. Determine the fuel flow in kg/hr.

15 30 50 per page