instruction stringlengths 31 24.3k |
|---|
I studied work-energy theorem and the equation for mechanical energy conservation yesterday. I’m not able to understand how to identify forces when choosing a system (which force is which).
This is how my textbook derived the equation for mechanical energy conservation, using the work-energy theorem : ($W$ is for work... |
This is from A.P. French Special Relativity book, Chapter 3 (page 78)
Setup of the proof: $S$ and $S'$ be inertial reference frame. $S'$ move to the right with respect to $S$ at velocity $v$.
Let co-ordinates in $S$ be $(x,t)$ and co-ordinates in $S'$ be $(x',t')$
Equation (3-8) in the book, he writes that transformati... |
In the question :
Relationship between temperature and energy
The relation between energy and temperature is given : $(1/2)k_BT$ per degree of freedom.
Then the one that gives the accepted answer gives further comments on the energy at particle colliders like LHC, and say that one uses $E=k_B T$.
Why for the equivalen... |
In ''An intro to QFT (2018)'' chapter 3, Peskin does the following:
Let me introduce some notation first, let $v^s_k=\begin{pmatrix}\;\;\,\sqrt{k\cdot\sigma}\,\xi^{-s}\\-\sqrt{k\cdot\bar{\sigma}}\,\xi^{-s}\end{pmatrix}$ be a bispinor for the negative-energy solution to the Dirac eq. with momentum $k$ and spin state $\x... |
Over here,
https://cdn.discordapp.com/attachments/702561907961233459/714002823876182096/IMG_20200524_120155.jpg
In the solution to this question, it says that maximum kinetic energy change occurs when the energy goes into exciting one of the hydrogen's electron into a higher energy state. What is the mechanism of this?... |
Here is a picture of the given circuit. Initially the switch is connected to the left side, and the question is what are the charge and potential difference across each capacitor ( capacitance is in $\mu F$ ).
I want to make sure my understanding of this problem is clear. Here is my analysis. Before the switch is clo... |
In the time independent perturbation theory, the perturbed wavefunction is [1]:
$$ \left|n^{(1)}\right> = \sum_{k\neq n} \frac{\left<k^{(0)}\right|V\left|n^{(0)}\right>}{E_n^{(0)}-E_k^{(0)}}\left|k^{(0)}\right>$$
However, if the $\left|n^{(0)}\right>$ is degenerate, the denominator would become zero and the term would ... |
I really confused if there is a function (mostly in physics, functions represents physical quantities) which is not a field? I feel all functions in physics are fields. Is there any functions which are not fields?
I see a lot of questions in stackexchange about functions and fields. But no one nail down the difference ... |
My friend, Nima Fathali, used to claim that the fact time dilation can be deduced from the (non-)simultaneity though I used to claim otherwise saying that these two qualities are independent of each other. Defending his claim, he said that if we assume too many clocks located close to each other along, say, the $x$-axi... |
I know $\mathrm{J} = \mathrm{N\ m} = \mathrm{C\ V}$, but what if I want joules expressed in SI base units of $\mathrm{kg}$, $\mathrm{m}$, and $\mathrm{s}$? This is trivially easy if I use $\mathrm{N\ m}$ to get there:
$$\mathrm{N} = \mathrm{kg\ m/s^2}$$
ergo using only SI base units to derive $\mathrm{J}$ we get
$$\mat... |
According to the Faraday law, voltage will be induced in the generator when the the loop will move in a magnetic field. This voltage will cause the current in the circuit.
My question is
Do charges flow in the segments $a-b$ and $c-d$ of the loop also, or do these segments just give the voltage and then the charges j... |
Long delayed echoes (LDEs) are radio echoes which return to the sender several seconds after a radio transmission has occurred.
Do LDEs occur on other planets and moons too? Like for example on Mars, Moon, Venus, Titan etc.
|
Imagine a box on a flat, frictionless plane traveling in a single direction with momentum mv. Now imagine a step in the plane. When the box hits the step, it will either stop completely or it will roll over the edge and keep moving.
How do I know which will happen for a given height of box, height of step, mass/veloc... |
The Theorem about quantum operators commutation relation says:
Consider pairs $(U, V )$ of unitary representations on a
Hilbert space $H$, satisfying the commutation rule:
$$U(x) V(y)=\exp (i \omega(x, y)) V(y) U(x).$$
Such pairs are all equivalent to
multiples of the standard Schrödinger representation on $L^... |
Calculate the dispersion relationship and density of state of the 2D simple triangular lattice. Suppose the atomic mass is m, the distance between adjacent lattice points is a, and the atoms of adjacent lattice points are connected by a spring with elastic coefficient f. Numerically calculate the density of states.
T... |
Force can be found from potential energy:
$$\vec{F}=-\nabla U$$
In other words, force depends on how the potential energy changes in space, but not on the potential energy value?
Or if we take some constant distance between two points, in case of a stronger field, will there be a higher potential difference than in th... |
I'm not thinking of even particles from a nuclear power-plant or man-made event. If a high-velocity highly-interacting particle made it through all the natural protections that keep life in a non-crispy state and by some highly improbable chance collided with one of the atoms that help to make up a (potentially unfortu... |
I am currently trying to understand load cells in the measurement of impact forces from falling objects and just had a thought experiment that I do not quite understand how to calculate.
What is the difference in impact force when a soft material is placed on the surface vs below another hard surface.If I were to use s... |
We know that magnetism is just a illusion created because of special relativistic effects and there is only electric field which is really there in reality.
so how can we say that this imaginary magnetic field which is just an illusion of relativistic case of charge motion, gets converted into electric field when we ta... |
Whilst reading Light Sterile Neutrinos: A White Paper it is stated on the bottom of p.3 without an explanation that:
"The observed $Z$-boson decay width implies that any additional active neutrinos are quite heavy, $m_\nu \gtrapprox M_Z/2$."
Where was this observation deduced from? Is it from Heisenberg's uncertainty... |
There's a nice answer to this question: Why is the scalar product of two four-vectors Lorentz-invariant? - that explains that a Lorentz transformation is one under which the inner product of two 4-vectors is invariant.
I know that the norm of the difference between two 4-vectors can be interpreted as the spacetime sepa... |
What if we modify the double-slit experiment to have the path between slit $A$ to the board shorter then the path from slit $B$ to the board.
Will we still have an interference pattern? If the answer is yes, do we have a way to calculate path length from the $B$ slit to the board(assuming it's the only unknown)?
|
The Lagrangian density for the interaction term of the bosons $W_1,W_2,W_3,B$ in the electroweak theory is
$$
\mathcal{L}_g=-\frac{1}{4}\operatorname{Tr}(W^{\mu\nu}_aW_{\mu\nu}^a)-\frac{1}{4}B^{\mu\nu}B_{\mu\nu}
$$
The wikipedia article about Electroweak interaction claims that $W$ and $B$ are the field strength tenso... |
In his Lectures on Quantum Theory, Isham states the generalized uncertainty principle for two observables $O_1$ and $O_2$ for a pure state $|\psi\rangle$ as
$$\Delta_\psi O_1~\Delta_\psi O_2 \ge {1\over 2}\Bigl|\langle\psi|[O_1,O_2]|\psi\rangle\Bigr|.$$
Question: To generalize this to a mixed-state with density matrix ... |
For a science project I chose to investigate the relationship between the resonance frequency of cups and the amount of water filled in it. I filled the cup with 10 grams of water each time, and used a pencil to hit the cup. After trying a lot of combinations, I found that there is a linear relationship between $1/f^2$... |
I wanted to know how the electron density in metals behaves with temperature. I couldn't really find an answer online so I searched through my x-years old scripts and, surprisingly, I found a sentence in a lecture:
Metals: Electron density will be influenced only slightly with
temperature because the fermi distribut... |
Scenario:
Two fighter jets at an airshow are flying towards each other at 1/2 the speed of sound. (Their paths are offset so they will not crash.) When the pass each other, will either pilot or a spectator on the ground hear a sonic boom?
|
In multiloop circuits where we have to apply Kirchoff law, with multiple batteries, I am having a bit of difficulty figuring out what direction and from which battery would the current originate.
For example take this circuit where would the current originate and why and in which direction?
|
I was solving a question about perturbation theory and I came across something my teacher didn't mention and I can't seem to understand it. In the question there is an external electric field on a H-atom. I can neglect hyperfine structure and lamb shift. The atom-field interaction term in the Hamiltonian is
$$−\vec{d... |
If the hydrogen emits four distinct light frequencies as a gas and on the Sun surface the gravity cannot alter hydrogen state as a gas does the yellow component of sunlight come from its interior?
|
In an answer here I read:
You need slow neutrons because if the neutrons are too "quick" then they scatter of the atoms instead of being captured by them. You can imagine a big lump of playdoh and a much smaller ball of playdoh. If you shoot the small ball with high velocity at the big lump then the ball is scattered ... |
I understand what diffusion of mass or diffusion of heat means. I know that the conversion of the dynamic head of the flow into static pressure in a stator or diffuser is called 'diffusion'. But in the case of diffuser what is being 'diffused'? What is 'diffusion' in a stator/diffuser?
|
Can every idempotent density operator be written in the form $$\sum_ic_i|i\rangle\langle i|,$$ where $\{|i\rangle\}$ is an orthonormal set and $\{c_i\}$ is a set of coefficients (Edit: Without assuming that the vector space on which the density operator operates is finite dimensional)?
It seems like people are assuming... |
Imagine an open quantum system interacting with an environment that admits a density matrix (Markovian) description in terms of Lindbladians ($c$ and $c^\dagger$). Is there a meaningful way to define a single particle Green function for this system up to the time the steady state is achieved, but without knowing any m... |
In Shankar's QM (second edition, p-282), There are some equations are given, They are following as,
$$T(\epsilon)|x\rangle = |x + \epsilon \rangle$$
where $T(\epsilon)$ is Translation operator.
I understood equation given above, but Shankar says, "X is basis is not unique" then general result should be given as below,
... |
We know that the current symmetry of GSW is $SU(2)_{fermions, left}*U(1)$, and the correct representation of the $SU(2)_{fermions, left}$ is the $2+2$ representation.
I want to know what is the reason we don't consider the symmetry group to be $SU(2)_{lepton, left}*SU(2)_{quark, left}*U(1)$?
Considering quarks and lep... |
I recently came across this problem, in David Morin's weekly problem set. The solution to which I figured, as explained here. But I also came across the solution explained in this report. Here the author solves the problem in n dimensions too and concludes that in 2-dimensional space, the object that gives maximum fiel... |
How can the integral of a topological term (like the Nieh-Yan term) on all of a compact manifold be nonzero whereas it's a total derivative and the manifold has no boundary?
I assume the manifold can be covered with one coordinate patch.
I am specifically considering the index for chiral anomaly on a compact manifold.
... |
How does an electron add up (enters) in the valance shell of an atom? Why is energy released when an electron adds up in the valance shell of an isolated atom.
|
I recently saw that the dust on the airplane's wings are frequently cleaned by some human workers (generally after every trip, workers clean the fine dust on wing's surface by hands). But I have a doubt. I thought that when the airplane is travelling at a very high speed in air, the dust will cleaned off due to the he... |
How much light is needed to convert elements from a lower-state-of-matter such as from a solid directly to plasma without a liquid state, if that is possible?. Which element would produce the most reaction or matter-change, no matter the state, per photon? Is there a list of some type?
|
So imagine space is a regular square mesh or lattice. In a theory like QCD, the photon lines are placed along the edges of this graph to form paths.
The space is supposed to represent simple Minkowksi space in the limit when the lattice points approach zero.
So what would a graviton (a quanta of curvature) be like in t... |
When I read Reddy's book, "Energy Principles and Variational Methods in Applied Mechanics", Chapter 5.1. I am confused with the two jargons "the principle of virtual displacement" and "the principle of virtual work". They are used interchangeably without clarification. Could someone explain the difference between them?... |
From Wikipedia, the Minkowski metric is defined (using (- + + +) signature) as :
$$\eta_{\mu \nu} = \eta^{\mu \nu} = \begin{pmatrix}
-1 & 0 & 0 & 0 \\
0 & 1 & 0 & 0 \\
0 & 0 & 1 & 0 \\
0 & 0 & 0 & 1
\end{pmatrix}$$
I am a beginner in tensor calculus, and feel uneasy that a covariant vector is being equated t... |
My father was colorblind, and I always wondered if colors were a matter of physics or if different colors are just a human way of describing and differentiating our visual perception of the world?
For example, is the color blue by nature blue, or is it just what we see?
|
A ladder is positioned against a wall, it forms a $30^\circ$ angle with the floor. A person that was holding the ladder releases it. The ladder starts accelerating down and to the right. The wall is frictionless but the floor is not.
I did the $\mathrm{FBD}$:
Where $F_g$ is the ladder's weight, $N_w$ the normal force ... |
Considering that the spontaneous fission rate of uranium 235 is 0.00563 fissions per Kg per second, why does this not cause small explosions or "fizzles" of the sub-critical fuel mass(s) in an atom bomb in the hours before the assembly of the critical mass is triggered? By similar reasoning, why doesn't spontaneous fis... |
Actually I've got few questions. I've seen an experiment in which a box with hole drilled in it, when viewed from Infrared camera, shows the radiation emitting from it.
Q1: So, is a Black Body an efficient way to convert visible spectra light to infrared light?
Q2: Also, can you create an IR laser from a Black Body?
Q... |
I am looking for good references (pdf papers) that discuss and justifies the use of the "modified" dot product:
\[
{\langle}A,B{\rangle}=-A^0B^0+A^1B^1+A^2B^2+A^3B^3
\]
in the 4-dimensional space time metric (Lorentz, Minkowski) by way of basic principles using just ideal clocks and light signals. I tracked down A.A. ... |
In this video, explaining the intermediate axis theorem (Dzhanibekov-effect) in a very nice way (around 7:52, from the perspective of the co-rotating frame where centrifugal are present) one can see (starting at 1:12) that the axis of rotation of the wingnut itself starts to rotate (on subsequent momentary cones with t... |
I often read about magnetic islands forming as a result of magnetic reconnection?
To my understanding, those are irregularities of the magnetic field right? If not, could someone help me understand this concept?
|
I'm an amateur studying General Relativity (GR). A basic question on which I'm still unclear is the sense in which GR reduces to Special Relativity (SR) in the limit. I understand that the laws of SR apply locally, as Euclidean laws apply locally on the surface of the earth. But am I wrong that tidal effects will not ... |
This question is motivated by the first problem in the second chapter of Modern Quantum Mechanics (by J. J. Sakurai).
I want to find the time evolution of the spin operators ($S_x,S_y,S_z$) in the Heisenberg picture of an electron ($e<0$) subject to the following Hamiltonian:
$$ H = -\frac{eB}{mc}S_z=\omega S_z, \... |
The problem is the question 5.67 of Hecht book - Optics
Suppose two mirrors (A and B) are 25 cm apart and a small candle is placed in between them such that you
cannot see it. You see the images at $Q_{1}$ and $Q_{3}$, and they seem to be $10$
cm apart. Where is the candle located?
But in optics textbook by S. Parkins... |
From my basic understanding of Time Crystals, we need a periodically driven Hamiltonian, say $H(t)$ with period $T$, $H(t)= H(T+t)$ and a local order parameter $O(t)$ with a period $nT$ satisfying rigidity and the periodic behavior should persist in the thermodynamic limit (Ref: https://arxiv.org/pdf/1908.11339.pdf). R... |
Suppose a ball is spinning through mid air. We know through the Magnus effect the way the ball will go. On the side where the air flow is slowed down due to the spin of the ball, the pressure increases because of Bernoulli's theorem (which, unless I'm wrong, states that pressure and speed/velocity are inversely proport... |
In an electromagnetic filed, if we choose:
$$E_x(z,t)=\sqrt{\frac{2}{V\epsilon_0}}\omega q(t)\sin(kz)$$
$$\text {and}$$
$$cB_y(z,t)=\sqrt{\frac{2}{V\epsilon_0}}p(t)\cos(kz)$$
How to prove the commutation relation: $$[\hat{q}(t), \hat{p}(t)]=i\hbar$$ for the photon states?
|
The Onsager solution for specific heat is
$$C\approx -Nk\frac{2}{\pi}\bigg(\frac{2J}{kT_c}\bigg)^2\ln\Big|1-\frac{T}{T_c} \Big|\qquad (T \textrm{ near } T_c)$$
Critical exponent $\alpha\neq 0$. Neither it follows a power law. But when we talk about scaling relation or the result we get for mean-field calculation, we sa... |
Consider two drummers: W and E. They meet in the middle of the country and synchronize. W strikes his drum on the up-beat, E on the down-beat. They remain forever permanently synchronized, each with a pendulum swinging side-to-side (50% time to left, 50% of time to right).
W goes to the West coast, E goes to the Eas... |
The Aharonov-Bohm effect is discussed for the case of particles moving along a closed loop through a region with zero magnetic field, however I was wondering whether it still holds for arbitrary fields where particles move through regions with arbitrary non-zero magnetic fields. I suspect this still applies.
The reason... |
In my text Schwartz writes: since $\bar{\psi} \gamma^\mu \psi$ transforms like a 4-vector, we can deduce that
$$\Lambda_s^{-1} \gamma^\mu \Lambda_s = (\Lambda_V)^{\mu \nu} \gamma^\nu, \tag{10.78}$$
where $\Lambda_s$ and $\Lambda_V$ are the Lorentz transformation acting on Dirac spinors and 4-vectors, respectively.
In t... |
Let's consider for instance an infinite plane sheet of charge: you know that its E-field is vertical and its Absolute value is $\sigma / 2 \epsilon _0$, which is not dependent on the observer position.
How is this physically possible? An observer may put himself at an infinite distance from all charges and he will rece... |
in all my physics courses I have been told that magnetic field lines are absolutely closed lines. It is well explained in this wikipedia page, which states:
A magnetic field has no sources or sinks (Gauss's law for magnetism),
so its field lines have no start or end: they can only form closed
loops, extend to infi... |
In the double-slit experiment, if we could make the electron traveling through slit $A$ to travel longer distances then the electron traveling through slit $B$, what would be the result?
I was trying to ask that question earlier, but I didn't realize the untrivial problem of setting up such an experiment. The challenge... |
I am reading Nakahara Geometry, Topology, and Physics. In the section on fermionic harmonic oscillator, after some math, the partition function is given by
$$\begin{aligned}
Z(\beta) &=\mathrm{e}^{\beta \omega / 2} \lim _{N \rightarrow \infty} \prod_{k=-N / 4}^{N / 4}\left[\mathrm{i}(1-\varepsilon \omega) \frac{\pi(2 n... |
An unknown particle with rest energy of $1 \text{ MeV}$ is traveling with a speed of $0.6c$ along the $x$-axis in our rest frame when it decays into two
photons, also travelling along the $x$-axis. What are the energies of the photons in $\text{MeV}$?
I've been trying to learn special relativity recently and came a... |
For the medium let’s use water. When light passes through water its wavelength decreases. It’s frequency stays constant. It changes its direction upon entering the water unless it enters the water orthogonal to the surface. It exits the water at the same angle it enters. The current explanation for this is the absorpti... |
We know that when we connect a conductor to a source of potential difference, an electric field is established inside the conductor. With the help of calculations which I show below, we can see that electric field distribution inside the current-carrying conductor takes different forms depending on the shape of the con... |
Today, during a thunderstorm, the lamps in the room suddenly flickered and then gradually became brighter in less than a second. The lamps remained brighter than normal for a few seconds before returning to normal. Can someone explain to me the physics behind this occurrence?
|
I found that sometimes people mentioned that Hamiltonian in real space or Hamiltonian in reciprocal/$k$-space. I wonder what difference of Hamiltonian in real and reciprocal spaces are?
For example, the tight binding Hamiltonian for pristine graphene is written below.
$$H=-t\sum_{\langle i,j\rangle} a_{i}^{\dagger}b_{j... |
To explain my question, I'll use an example. Let's say that I have a soda can and I apply $10$ N force from the right as well as from the left. Here, the net force is zero, yet the can will get deformed.
My question is: How can an object be deformed with no net force?
|
In the RI talk https://www.youtube.com/watch?v=_8bhtEgB8Mo at 1:00:30 a member of the audience asks about the race between the big crunch and the rate at which someone falls into a black hole. The argument is that since it take Alice an infinite amount of time from Bob's point of view to fall beyond the event horizon, ... |
Let's assume that we consider a bunch of particles (e.g. water or air) and we describe their velocity using a vector field $\vec v(\vec x, t)$.
Moreover, let's assume that there is no external potential and hence the total energy is just an integral over the kinetic energy:
$$ E = \int d^3 x \; \rho \frac{m}{2} \vec v... |
Here, In Shankar's (2nd edition, p-283) QM book, The translation operator is given by
$$T(\epsilon) = I - \frac{i\epsilon}{\hbar}G \tag{11.2.13}$$
Similar In Sakurai (Revised edition 1994 p-45), he wrote about equation as following,
“We now demonstrate that if we take the infinitesimal translation
operator to be”
$\m... |
I am working on a scientific project for my university and I am reading a german paper (Karas: "Platten unter seitlichem Stoß") which makes use of generalised coordinates.
It's about an analytical solution of the impact of a ball on a plate.
At some point, he defines the potential energy for the plate $(a,b)$ as:
$$\t... |
Working on a research problem in the continuum mechanics of fluids. For clarity, uppercase will be used for tensors in the reference configuration, and corresponding spatial items will be in lowercase.
For a moving body, define a map $\Phi:(X,t)\to{(x,t)}\;$ from a reference configuration to spatial configuration, whos... |
While reading the Wikipedia page on the P function, I came across the following consideration (paraphrasing from there):
Given a state $\rho$, if we write it in anti-normal order as $\rho_A=\sum_{jk}c_{jk}a^j a^{\dagger k}$, and
$$\rho_A(a,a^\dagger) = \frac1\pi\int \rho_A(\alpha,\alpha^*)|\alpha\rangle\!\langle\alp... |
I believe this question has been asked $>666$ times already, however I am trying to analyse it from a different perspective.
Consider the completely theoretical case of an ideal voltage source ($0 \,\Omega$ internal resistance) having its terminals connected to one another through an ideal (perfectly conducting, zero r... |
I am trying to find a picture of the $N$-body simulations that shows the LSS. Particularly I am looking for different neutrino masses without the CDM. For instance pictures likes this
But with more varying/different neutrino masses. I am looking for articles
|
Let's say that a body $A$ possesses a charge of $-1 \text{ e}$ (electron) and another body $B$ is electrically neutral (has a charge of $0 \text{ e}$). Now, if we bring any two objects in contact, from an electricity point of view, there would be an exchange of electrons so that both the objects posses a charge of the ... |
The Wikipedia article on expansion of the universe states that:
expansion is an intrinsic expansion whereby the scale of space itself changes (...) the metric governing the size and geometry of spacetime itself changes in scale
But at the same time it states that it only affects gravitationally unbound parts, which w... |
The Hawking temperature of a Schwarzschild black hole is given in SI units as
$$T_{H}=\frac{\hbar c^3}{8 \pi G k_{B} M},$$
where $k_{B}$ is the Boltzmann constant. I would like to know how $\hbar$ and $k_{B}$ show up in the temperature. I mean where in the original derivation by Hawking do these constants show up?
I ha... |
I have a paper on electric potential energy, it should be noted that the topic was not in anyway explained back when we were on campus so whatever little understanding i have of the topic right now is the result of relentless googling for a week or so, the wiki page divides electric potential energy into two sections:
... |
I've never studied physics before and I'm a Maths major. But I do have a physics-related differential equation question which I need help on.
Given the beam deflection equation:
$$F(x) = EI \frac{d^4u}{dx^4}$$
where $E$ is the Young's Modulus, $I$ is the moment of inertia.
I found that $u(x)$ implies the displacement, ... |
I am on my way to general relativity, but I am struggling with the covariant derivative.
At this point I am trying to ignore the spacetime character of the world i.e. I am trying to understand what a covariant derivative means in an intrinsically curved space, without taking into account, that time is also effected by... |
In the picture there are feynman diagrams for two reactions. My question is: Why aren't 6.3 and 6.4 possible for the first reaction? And as a sidenote, I don't really have a good source for the rules, my professor only did a incomplete lecture about the subject. Is there a good source to read more about feynman diagram... |
I am confused about the solution to the Dirac equation and how it corresponds to left-/right-handed Weyl spinors. In Srednicki, page 242, it is stated that taking the ultrarelativistic limit ($|\bar{p}|>>m$), projects the solutions of the Dirac equation to purely left- or right-handed spinors.
From the Dirac equation:
... |
I live in the UK at approx. $53 ^\circ$ latitude.
The horizontal component of my centripetal acceleration due to the Earths spin works out at $1.3$ N.
That's like the weight of an apple.
Is that right?
I mean it's more than I would have thought.
Surely that is significant enough that say builders and athletes etc must ... |
I have suddenly trouble understanding kinetic energy and why a moving particule have an energy.
I believe particules can only interact via forces.
So to do work, at the end of the day a moving particule would need to apply some force in order to push another particule. But which force is it using? Like electromagnetis... |
Given a Quantum Hamiltonian: $$\hat{H}=ax^2+bp^2$$ It does not commute with either $x$ or $p$. Suppose we have a Hamiltonian :$$H = k \hat{p}\hat{x}$$ why do we need it to be: $$H = k (\hat{p}\hat{x} - \hat{x}\hat{p})$$ And why can't we leave it in the former form? What can be the possible reason we don't have Hamilton... |
I have kind of a paradoxal question about two sticks connected through a hinge that rest on a frictionless floor at the bottom and frictionless walls on each side at the top.
What are the forces in the hinges if the total weight of the sticks is equal to 2*F (F the weight of each stick seperately, the hinge is consider... |
So, this is how it is typically done. We have a reference frame $S$ and the coordinates $(x,t)$ of an event, $E$ (or collection of events which we call world-lines) are mapped onto a 2-dimensional physical paper. (Typically $x$ is horizontal axis and $t$ is vertical axis and the two axis are orthogonal)
Now we analyse ... |
When reading about "active-sterile mixing", which requires some Dirac mass ($m_D$) and some Majorana masses ($M_R$) to be very small but not zero, the seesaw limit model is discussed ($M_R \gg m_D$).
In this paper (Light Sterile Neutrinos: A White Paper), it is mentioned that the active-sterile mixing matrix, when squa... |
I'm in the middle of writing a PDEs assignment and I thought I'd use the wave equation for a horizontal string with gravity. Easy I thought: $u_{tt} = c^2u_{xx} - g$. We solved it without gravity. Then added gravity: I set up the question on what the steady solution looks like, and I got a parabola.
But wait, I know... |
Every electromagnetic radiation contains particular frequency(f), Wavelength(l) and Amplitude (a). Frequency and Wavelength categories the wave (Infrared , Radio etc) and will be constant. But Amplitude decreases over time. It can be because of propagation or losses.
So i want to know how the colours in visible spectru... |
Why do scientists need to measure extremely small intervals of time? Why is it necessary?
|
Consider a system of two particles of masses $m_1$ and $m_2$ moving in a plane. Let the respective position vectors be $\mathbf{r_1}$ and $\mathbf{r_2}$. The particles are attached at the end of a massless rigid rod of some length $l$. Since this is a holonomic constraint,
$$(\mathbf{r_1-r_2})^2-l^2=0$$
The system sh... |
In today with COVID 19, we should wear the mask all day. My teacher in Korean high school said "If you want to play basketball, you could play with wearing the mask" to me. My friends and I wanted to play basketball, so we played basketball wearing a mask. But it was very hard to exercise with wearing the mask. I could... |
According to this resource on Maxwell theory in curved spacetime, the form of the field strength tensor is independent of the choice of coordinates:
$$F_{\mu \nu} = \partial_\mu A_\nu - \partial_\nu A_\mu$$
regardless of the choice of coordinates $x^\mu$. However, in many coordinate systems the coordinates chosen do no... |
Wikipedia's page for 'List of gravitational wave observations' has a location table called 'Location area (deg^2)'. Just to be sure, if you click on 'deg^2' it takes you to the 'square degree' page....
The values range from 16 to 1651, with two different events at 1033.....
But if gravitational waves can reach us from... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.