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I am looking at setting up an
Hanbury-Brown-Twiss (HBT) autocorrelation experiment to detect single photons of light in the wavelength range of 600 nm to 1600 nm. I will need two APDs / SNSPDs, a time-to-analog-converter / single-channel-analyzer module, and some time tagging electronics. I was wondering if there is a... |
I have understood the most of the equations that lead to the Fresnel-Equations from electromagnetic waves and Maxwell equations. But not enough to understand what is happening. So I don't ask for an answer under what circumstances, what equations lead to which results, but what physically is happening.
What at a surfac... |
On page 310 of the third edition of the textbook, Schutz writes:
Suppose now we assume $M u \ll 1$ but is not entirely negligible. Then if we define
$$
y:=u(1-M u), \qquad u=y(1+M y)+\mathrm{O}\left(M^2 u^2\right)\, .\tag{11.52}
$$
My question is how to derive the second relation. I can see if one starts with a firs... |
I'm aware that I've likely made a very simple error/misunderstanding here, but I have some confusion about the divergence of an electric field of a point charge which should be zero at all points in space asides from the location of the charge. When I try to determine the divergence at some points I don't see the diver... |
I have a continuous-variable quantum state which is entangled between two subsystems, that is,
$$\left|\psi_{AB}\right\rangle=\int_{-\infty}^{+\infty} dq_{1} dq_{2}~ \psi(q_{1}, q_{2}) \left|q_{1}, q_{2}\right\rangle, \tag{1} $$
where $\left\lbrace\left|q_{1}, q_{2}\right\rangle \right\rbrace= \left\lbrace \left|q_{1}\... |
Schroeder chapter 5 discusses the following relationships between work and potentials $F$ and $G$
$$\Delta F\le W$$
$$\Delta G \le W_{other}$$
where $W$ corresponds to any kind of work done on system, not just $PV$ work, ie. $W=-P\Delta V+W_{other}$ where $W_{other}$ is non-$PV$ work like electrical work. I am wonderin... |
In a recent talk, Sean Carroll explicitly claims that, in Everett, world branching
occurs when two decoherence makes worlds "so different" that interference will
no more become observable between them, or when they will no longer be able
to interfere for some reason.
I am not really sure what that could exactly mean, b... |
I have done the following work. Consider the following pendulum and measurements:
Assume the length of the pendulum is $r$. Then the following calculations can be done:
$h_{max} = r - r\cos{\theta}$
$U_g = mgh_{max} = mg(r-r\cos{\theta}) = \frac{1}{2}mv^2 = KE \implies v_{max} = \sqrt{2g(r-r\cos{\theta})}$
We are solv... |
I was watching a video about rotational kinetic energy in which they derived the formula $$K=\dfrac{1}{2}mv^2+\dfrac{1}{2}I\omega^2$$
each point on the circle has a translational velocity equal to the velocity of the center of mass $v_{CM}$, and a tangential rotational velocity $v_i$.the derivation is similar to the fo... |
I'm trying to understand how to perform a unitary transformation on a set of traceless orthonormal Lindblad operators, following chapter 3.2.2 of The Theory of Open Quantum Systems by Breuer and Petruccione (also similar to this wiki page).
From equation 3.72 of the book, a set of traceless orthonormal Lindblad operato... |
I understand that multiple transit detections of an exoplanet are almost always used to derive its period, but is there a way to do it with only one transit detection? As in, with only one available light curve? I'm assuming we already know the masses/radii of the exoplanet and host star. I've searched online for an an... |
Is it possible to fix an inertial frame to a photon moving in vacuum?
If yes, what is the speed of another photon moving in vacuum with respect to this frame?
What is the proper time measured by the second photon between two events?
Please provide references for the answers.
|
After about 11 seconds, regardless of what frequency the system is driven at, the waves will succinctly cancel.
https://phet.colorado.edu/en/simulations/wave-on-a-string
How?
I was playing with it earlier and thought the time at which it occurred would change with changing frequency... it does not!
|
Why are colour shadows formed? I have three coloured glasses in my house and If I keep my hand in its light path, I am seeing coloured shadows on the opposite wall.
Why is this happening?
Also currently only orange and blue shadows are visible (from the bottom and middle window light) . But, if I take my hand a littl... |
How can you write the partition function for non-polar and polar dielectric materials? For dipolar dielectric materials we can easily write partition function; it is proportional to $\exp(-\beta\mu E \cos \theta)$ where $\mu$ is the dipole moment and $E$ is applied field. Is there a similar expression for non-polar ... |
Consider a kinetic lagrangian of 2 Klein-Gordon-Foch fields $\varphi$ and $\chi$ with interaction term
$$\mathcal{L}_I=g^2\bar{\chi}\chi\bar{\varphi}\varphi.$$
Is theory with such interaction renormalizable? Is there any proof?
|
String theory admits a vast number of vacuum solutions, which I gather come from the all the ways of compactifying the geometry of spacetime down to 3+1 dimensions using Calabi-Yau manifolds. I have always been unclear on the status of actually identifying/constructing solutions that exactly match experimental observat... |
The condition for both the dynamical horizon and an apparent horizon is that expansion of outgoing null normal $\theta_l$ = 0 and expansion of ingoing null normal $\theta_n$ < 0. Then what is the difference between an apparent horizon and a dynamical horizon?
|
in my book it is written,
"pumps are used to transfer liquid from low-pressure zones to high-pressure zones."
but if we talk in general, fluid transfers from high-pressure zones to low-pressure zones. can anyone please elaborate on the above statement?
|
For calculation purposes, let's say it's a cone with cone angle (at Earth's center) of 30 degrees, that extends down to the outer surface of Earth's solid inner core, and the entire mass is ejected over the span of one minute. I have some educated predictions, but I would really appreciate some scientific, source-backe... |
Specifically, why is the operator “sandwiched in” between $\Psi^*$ and $\Psi$? i.e. Why isn’t the formula just $$\langle \hat{Q} \rangle = \int \hat{Q}\cdot|\Psi|^2 dx = \int \hat{Q}\cdot\Psi \cdot \Psi^* dx$$ instead of $$\langle\hat{Q}\rangle = \int \Psi^* \cdot\hat{Q}\cdot\Psi dx~? $$
I get that operators are gene... |
To explain more clearly, I am looking for how one would derive an expression for the capacitance of a system which consists of two conducting spheres of radius $a$ separated by a distance $d>2a$. I found the following solution on the Wikipedia article on Capacitance, however no explanation is given:
\begin{align}
\math... |
Far as I can tell, the force generated by electromagnetic field can be seen as an electrical force or as a magnetic force depending on the observer, i.e., these forces are actually the same phenomenon experienced differently, according to special relativity.
Do any of the other fundamental forces exhibit such relations... |
I have an Hamiltonian of this form:
\begin{equation}
H = \frac{p^2}{2m} + V(x),
\end{equation}
I would like to approximate the time evolution for a time $\tau$ of a known initial Gaussian state $|\Psi_0 \rangle$ with known moments of $x$ and $p$ with (let $\hbar = 1$)
\begin{equation}
e^{- \mathrm{i} H \tau} \approx L_... |
In the book of $\textit{The Quantum World of Ultra-Cold Atoms and Light: Book 1 Foundations of Quantum Optics}$ by Peter Zoller and Crispin Gardiner on page 75, they derive the phase-amplitude stochastic differential equation for a thermalized oscillator.
From a complex Ornstein-Uhlenbeck process of the form
\begin{equ... |
The recurrence theorem of Poincaré tells us that EVERY open set in the phase space will be crossed infinitely often. It doesnt matter if the open set is a neighbourhood of the initial data set or not.
In Quantum Mechanics there is a recurrence theorem as well. It states that any system will return arbitarily close to i... |
As the magnet moves from the outside, the magnetic flux that is linked to the circuit is [pi_0 sin(wt)].
We have listed a series of processes related to electromotive force, self-inductance L, and current in a circuit.
The magnetic flux linking the circuit changes.
Electromotive force is generated according to Farad... |
Is there any difference in terms of fore/aft weight distribution between the two wheels in the two pictures?
In other words: Is the location of the center of gravity of the 100kg weight the only factor that matters for fore / aft weight distribution between the two wheels?
Assumptions made: Differences in the center o... |
Suppose we have a ring of radius $a$, placed on $xy$-plane and electric charge $q$ is uniformly distributed over it. Now, what is the potential due to this charged ring at some point in space $(r, \theta, \varphi)$? I looked at different places and I found different answers. Like in 'Classical Electrodynamics' by Jacks... |
If it is possible to collide two neutrons, how is it so? What particle accelerator or pre-collision processes are necessary and what results can be expected? If the products of neutron-neutron collisions are electrons, positrons and gamma rays, is it possible to transfer the resultant energy to another substance in ord... |
When I measure the leakage current of an active device, in this case an SCR, is that leakage current likely to stay roughly constant throughout the life of the device?
Why this is a physics question: The answer, it seems to me, relies on solid state physics knowledge that is more specialized than most EE's have. While ... |
For a classical system composed of two subsystems, is it possible to have a total entropy less than the sum of individual entropies of each subsystem
$$S(Z_1) + S(Z_2)> S_{tot}~ ?$$
|
When doing an inviscid fluid simulation, one typically uses the Euler equations. With these equations it is important to specify that there may be no normal velocity on the surface of an object (e.g. the cylinder below). Typically, this condition is specified as
$$u \cos(\theta) + v \sin(\theta)=0$$
with $\theta$ the a... |
I have a system of vector equations:
$$
\frac{\partial \vec{A}}{\partial t} = \vec{B} \\
\frac{\partial \vec{B}}{\partial t} = \vec{C} + \psi \vec{B},
$$
where $\psi$ is a scalar function. Say I want to solve this equation in a different coordinate system (which is just a rotation) defined by the transformation matrix ... |
How can i calculate force that is exerted on a vehicle when it hits an object?
Vehicle speed is 40 km/h, mass is 1500kg
Object is standing still (speed is 0 km/h), object mass is 11kg.
Now this vehicle is hitting the object at 40 km/h. How much force does the 11 kg object exerted on the vehicle?
Note: Object is not stu... |
I'm trying to intuitively understand proper time which is defined as the time that is always measured in a moving observer’s or particle's rest frame and is given by the equation.
$\Delta\tau = \sqrt{1 - \frac{v^2}{c^2}}\Delta t$, where $\Delta t$ is the coordinate time.
As such, what does the v term in the proper time... |
Suppose that we have the unit cell of a crystalline material. We want to calculate the Lennard-Jones (LJ) interaction energy between an hydrogen atom at a point $\mathbf{r}$ (inside the unit cell) with all the atoms of the material.
Since LJ potential decreases very rapidly, can I consider only the atoms inside a spher... |
The equation for the energy density in a region of space where there is electric field, $\epsilon_0E^2/2$ implies that energy in the electric field can only be positive. Consider, however, the energy of interaction between two oppositely charged objects, which is negative $-\frac{kQ_1Q_2}{r}$. Is it because we only con... |
In standard 1D textbook step potential problems, for $E>V_0$ with $V_0$ the step potential for $x>0$, one finds that for $x<0$ that eigensolutions are of the form
$$\psi(x) = A_1e^{i\sqrt{2ME/h^2}x} + B_1e^{-i\sqrt{2ME/h^2}x}$$
and for $x>0$ that
$$\psi(x) = A_2e^{i\sqrt{2M(E-V_0)/h^2}x}$$
where we've enforced unstated... |
I was reading a section of Introduction to Mechanics by Kleppner and Kolenkow:
where it talks about the same time dependence. I'm not very familiar with this term but was wondering if there was some proof or intuition towards both pendulums having the same time dependence.
|
In optics, we can use amplitude modulators as optical components to alter the amplitude of a wave. I'm currently working with simulating some propagations through space, and realize that an amplitude modulator gives a mirror symmetry in some instances. I'll try to explain the situation below:
Suppose we have an inciden... |
I have looked at previous questions on physics stack exchange and it has been really helpful, but this is my first time posting so I would be grateful for any information anyone can offer.
My question is, if the tangential acceleration of a pendulum equals -g*sin(theta), then does this mean it is linear fo... |
From textbooks (such as Optical Spectroscopy of Inorganic, Henderson, 2006) I know that the electric dipole moment operator is defined for one electron as:
$$
\hat{\mu} = e \hat{r}
$$
But then suppose I have a many electron wave function defined with a Slater determinant:
$$
\Psi = \{\phi_1, ..., \phi_n\}
$$
How do I d... |
The equation of state for and ideal gas states, $PV = mRT$. Since entropy is a state variable, can the equation of state be rewritten in terms of entropy?
|
I have read that the entropy change of a system is greater than or equal to the integral of the heat added to it divided by its temperature. The case where entropy is equal to the integral is when the heat is reversibly added, i.e., through an infinitesimal temperature difference and by implication, an infinitesimal he... |
In the reference $[1]$, the author presents the tensor quantities via its transformation laws. I'm pretty confortable with Pseudo-Riemannian geometry and tensors. But, when group theory enters the game, I can become a bit confused.
Firstly, some notation: $L^{\uparrow}_{+}$ is the proper orthocronos lorentz group; $L \... |
I'm reading semiconductor physics by Neamen and when the disscusion about the diffusion current density he wrote this (I'll cite the image from the book because it has an important graph that will help in clarifying the question)
My question is: How did he say that half of electrons at $x=-l$ will pass the the area a... |
(This might be somewhat related to a previous question I posted here, however it seemed different enough to warrant a separate post.)
I'm trying to see how, for a point charge at the origin, I might apply the differential form of Gauss' Law to integrate and find the electric field, for example along the $x$-axis:
$$\na... |
This is a strange question.
I can see particles in the air.They are not dust particles. They are smaller than a pin's point, and millions of them exist. If I put a pattern to them, the majority of them zoom down on a 90-degree angle from left to right and right to left. They bounce off each other, and then a random pat... |
Consider the case of someone riding a bicycle on an even horizontal surface at a constant velocity. As they are riding at a constant velocity, there is presumably a constant energy expenditure (which I will quantify by the power) to maintain that velocity.
For the sake of the question, ignore air resistance, but assume... |
Why in Newton's law of cooling the heat loss is proportional to the difference of tempretures. I mean how we know it is true? Why is it not $$\frac{dT}{dt}=-kt(T-T_a)$$ (linearly dependent on $t$) for instance? For example I can prove fundamental theorem of calculus so I know it is true but how do I know Newton's law o... |
The addition of
$$\mathcal{L}' = \epsilon_{\mu\nu\rho\sigma}F^{\mu\nu}F^{\rho\sigma} \propto \vec{E}\cdot\vec{B}$$
to the electromagnetic Lagrangian density leaves Maxwell's equations unchanged (shown here).
In Carroll's GR book, he appends the question: "Can you think of a deep reason for this?". What might this be? I... |
I learnt that the curvature tensor in 2+1D spacetime is zero in vacuum. How is it possible to come from there to the Newton's theory in 2D + time, where I guess, the gravitational force law is still possible in a for instance solar system made of disks.
If there is no curvature in empty space, the particles (planets) w... |
I got an infrared thermometer (SOVACARTE HS980E) recently and have been playing around with it.
My understanding is that it works by measuring the amount of infrared radiation coming off of the object, in terms of W per $m^2$, and then basically using the Stefen-Boltzmann law to determine what its temperature should be... |
Background:
By the equivalence principle, an observer (time-like geodesic + orthonormal frame (3 spacelike, 1 timelike) which serves as their measurement standard) in gravitational free fall sees physics which is locally indistinguishable to that they would see in an inertial frame in flat spacetime. As we well-know, m... |
Difficult for me to ask as I'm not a physicist.
Assume you have a water feature in the form of a waterfall where the water runs down a wall. On this wall, there are letters attached by a raised platform. The water travels down the wall and when it hits the perpendicular platform, travels parallel to the ground and off ... |
Sorry if this is long I am attempting to describe my entire thought process :
I am considering a situation for a barrel/cannon. There is a propellant (can be a cartridge filled with powder or what have you), and a projectile ( a bullet or cannonball), and they are encompassed in a barrel or tube. Left/back is the close... |
I was reading the ATLAS paper on the Higgs discovery and a question came to my mind. In the plot I attached, there are uncertainty bands on the background only hypothesis upper limits, and not on the observed upper limit.
Can anyone tell me why that happens?
Here is the link to the paper if anyone wants to read it: ht... |
Does the polarization spectrum TE measured by the Planck and WMAP satellites show evidence for superhorizon fluctuations at low multipoles and are these evidence for pre-bigbang inflation?
|
I am looking for a time-dependent solution to the Schrödinger Equation for the scattering of two particles. I am only looking for a schematic idea of how the state evolves, and the potential may be any uniformly attractive or repulsive potential. I would expect the initial conditions to be gaussian-like but this is als... |
I wrote a proof from first principles that energy is conserved in a $D$-dimensional rotating rigid body without external forces, and I'd like to ask for some feedback on improving my math with more idiomatic notation, perhaps making use of geometric algebra; my background is in machine learning, meaning I tend to do a ... |
Consider the following physical situation. Two position detectors are located next to each other, each one carries only YES/NO information on whether the particle hit that detector. A particle, let's say in a Gaussian state, is headed toward the two detectors. The width of the wavefunction of the incident particle is s... |
Is it possible to estimate the number of hot and cold spots of average diameter of 1° in a full-sky map of the CMB? (A full-sky spherical surface has 4pi sr or 41253 sq°). And does this number correspond approximately to the number of superclusters in the observable universe?
|
I am computing the von Neumann entropy associated with a density operator $\hat{\rho}$ which is defined for a pure state; that is, $\hat{\rho}^2=\hat{\rho}$. Besides, we compute this entropy in terms of the continuous eigenbasis of the position operator, that is,
$$S(\hat \rho)=- \text{Tr}\left[\hat\rho \log \hat\rho \... |
I've read online that black holes are almost ideal black bodies. But for a body to be called an ideal black body it should emit all the rays of all the wavelengths but black holes don't, so how can we call them black bodies?
so, what happens to the energy which black holes absorb?
|
My teacher said it's infrared but according to the graph shouldn't it be the visible region ?
Why aren't the graphs for black body radiation straight lines?
|
When I was thinking about mechanical forces being electromagnetic in nature , This question came to my mind ,
How do we exert such large forces when at the microscopic scale we moved such a small distance:
For example lets take a rod , If we press it with our palm at one of the ends and other end to the wall , we are a... |
So I was solving questions from my workbook and came across this problem. I don't know how to solve this.
QUESTION: Two vibrations at right angles to one another is described by the equations x=10cos(5πt), y=10(5πt+π/3). Construct the Lissajous figure of the combined motion.
|
The unitary time evolution operator is given by
$$\hat{U}(t)=\exp[-\frac{it}{\hbar}\hat{H}]$$
Meanwhile, the rotation operator about some axis along the unit vector $\vec{n}$ for a spin-1/2 system having only the spin angular momentum is given by
$$\hat{R}_{\vec{n}} (\varphi)=\exp[-\frac{i \varphi}{\hbar}\vec{n} \cdot ... |
We often hear this example of coordinate singularity. We can describe the 3D Euclidean space using rectangular or spherical coordinates. But in the spherical coordinate, the north pole $(r,\theta=0, \phi)$ is a coordinate singularity because one point here corresponds to infinitely many values of $\phi$.
In the Schwarz... |
I have trouble understanding a derivation in Griffith's QM: How to nondimensionalise Schrödinger equation to $$\frac{d^2\psi}{d\xi^2}=\left(\xi^2-K\right)\psi \quad .$$
The book explains it like so (at page 51). We start with the Schrödinger equation:
$$-\frac{\hbar^2}{2m}\frac{d^2\psi}{dx^2}+\frac{1}{2}m\omega^2x^2\ps... |
Is it possible to write down a certain kind of 'flow' or 'diffusion equation' where the direction energy flows always follows an entropy gradient?
|
It's known that in the kinetic energy spectra of electrons from the negative beta decays that at the end of the spectra some electrons are found to have a maximum energy that is equal to the energy difference between the initial and final decaying nuclear states.
Could the observation of such electrons suggest that neu... |
According to Griffith's Introduction to Quantum mechanics in section 1.5 Momentum, he said that " the expectation value is the average of repeated measurements on an ensemble of identically prepared systems, not the average of repeated measurements on one and the same system"
So, my question is what does the ensemble o... |
I was revising Electric Fields and it came up that if a positive charge moves in the direction of the electric field (so away from a positive charge), then the electric potential energy will decrease but if the charge is negative, it will increase.
This adds up when you consider work has to be done on the negative char... |
Given the Hamiltonian
\begin{equation}
H = \frac{p^2}{2m} + V(x)
\end{equation}
The propagator for a pure harmonic potential of the form
\begin{equation}
V(x) = \frac{1}{2} m \omega^2 x^2
\end{equation}
is given in the wikipedia article about propagators https://en.wikipedia.org/wiki/Propagator.
My Question is: What is... |
This may seem like an odd question for Physics, but I'm pretty sure this exact answer was given in this forum about six months ago, but I can no longer find the thread.
A rule of thumb was posted for pricing out large vacuum systems based on total volume. The context was the construction of small particle accelerator s... |
Suppose I have a ball moving through the air parallel to the ground, and diagonally in some 2D $x$ , $y$ coordinates (along the line $y=x$). Let's say its velocity is 1 units, which means on the $x$ axis and on the $y$ axis separately it's $\frac{\sqrt{2}}{2}$.
Modeling air resistance as approximately $F=Kv^{2}$, say w... |
Is it correct to assume that if there is only one object in the void (really empty void), then its location (the answer to the question “where” this object is) cannot be established?
You need at least two objects to be able to tell where each one is.
Or is it theoretically possible to specify where an object is in abso... |
$g$ effective at any latitude changes due to rotation of earth. Does it also change due to rotation when the body is at height or at depth or does it change only at the surface?
Edit: I am referring to variation in acceleration due to axial rotation of earth which changes with the latitude. Does it depend on the height... |
That half of the $ xz$-plane for which $x$ is positive is at zero potential except for the strip between $x = 0$ and $x = a$ which is at potential $Vo$. The whole of the $yz$-plane is at zero potential. Show that the potential at any point for which $x$ and $y$ are positive is:
$$\pi V = V_0 \left( \tan^{-1} \frac{y}{x... |
Hey I have a question about electric potential and its relation to objects.
As I understand it, Electric potential is a property of an object that depends on its surroundings and other objects around it unlike mass, for example, which does not depend on stuff around it. The mass of a football on earth or on the moon or... |
As written in the book Atom-photon interaction by Claude Cohen-Tannoudji, the time-evolution operator can be expressed as the Fourier transform of the Green's function
$$
U(\tau)=e^{-iH\tau}=\frac{1}{2\pi i}\int_{-\infty}^{+\infty}e^{-iE\tau}\left(G_-(E)-G_+(E)\right)dE
$$
where $G_{\pm}(E)=\lim_{\eta\to 0_+}G(E\pm i\e... |
I've bought a calcite crystal and tried to see birefringence by shining a laser through it.
I get a split spot in the centre of a sixfold pattern
The hexagonal pattern resembles a diffraction pattern, but I can't figure out what should cause it.
The crystal is not perfect, of course, however the hexagon does not depen... |
In Ref. 1 the author states:
The procedure of normal ordering allows us to define the physical Hilbert space. The physical meaning of this approach becomes more transparent in the thermodynamic limit $N\to\infty$ and $V\to\infty$ at constant density $\rho$. In this limit, the Hilbert space is the set of states that is... |
Whether the centrifugal force exerted by earth due to rotation be felt or even applied to us if we were in air ? The landmass rotates with earth so it is exerted on us radially outwards , but that isn't the case with air because we have wind speeds on opposite direction of earth too!
|
I am looking for a book with LOTS of problems in path integral quantum mechanics. I don't need a book with lot of theory. I need a book that has MANY problems of all difficulty levels. Essentially I need a problem book. Like there is a problem book called "Problems in Physics by I.E. Irodov". Like there is Schaum's ser... |
Consider a Lagrangian, $L$, which is a function of, as well as other fields $\psi_i$, a traceless and symmetric tensor denoted by $f^{uv}$, so that $L=L(f^{uv})$, the associated action is $\int L(f^{uv}, \psi_i)d^4x $.
To vary w.r.t $f^{uv}$ , I write:
$f^{uv}=f_{symm}^{uv}-\frac{1}{d}\eta^{uv} tr(f)$, (1)
where $tr(f... |
Suppose a boy is in a room with a bulb (no windows and other light sources). Now the boy ON's the bulb and OFFs it such that only one photon is released (hypothetical). Now the bulb is OFF. The photon should collide (elastically, so no loss in energy) with the walls and eventually after many collisions reach our eyes, ... |
$\vec{v(t)}\ =\frac{4t^{3}}{15}\hat{i} \ -\frac{3}{10} t^{2}\hat{j}$
$\vec{r(t)} \ =\ \frac{t^{4}}{15}\hat{i} -\frac{t^{3}}{10}\hat{j}$
Find
$\displaystyle \vec{r} \ \times \ \vec{v}$
I am working on the Kleppnor and Kolenkow mechanics book, in chapter two I am asked to find two vectors and then their cross product. I ... |
As I understand, the occupancy number in the nuclear shell model dictates the number of each type of nucleon that can occupy a specific sub-shell (angular momentum state l).
Note: s, p, d, f corresponds to l=0, l=1, l=2,... respectively.
My current understanding is that it works like this. The n=1 shell can be occupied... |
Is it possible to define time as the outward manifestation of the activities inside an atom?
For example,
one second is defined as the unperturbed ground state hyperfine
transition frequency of the caesium atom, which is 9192631770 Hz.
But if the caesium atom travels at higher speeds, then the atom will
have more kine... |
Let's suppose we have an equation that describes the minimum kinetic energy required for a rigid ogival projectile to perforate a target as a function of it's thickness T. Can we use this information to derive a more or less accurate mathematical model that describes the instantaneous resistive force acting upon the pr... |
I am studying the BCS-BEC crossover in atomic Fermi gases from this reference https://arxiv.org/pdf/1402.5171.pdf , but I am having hard times understanding some of the details.
In particular I can't understand equation 1.2:
$$
\frac{m}{4\pi\hbar^2 a_s} = \frac{1}{U} + \frac{1}{V}\sum_k^{\Lambda} \frac{1}{2\varepsilon_... |
I'm not able to quite understand this:
Consider a superposition of 2 opposite mechanical waves: when they interfere destructively, we say that the particles in the region of superposition have 0 intensity. I know it can be explained by the fact that the amplitude is 0 at that instant, but don't the particles have energ... |
For mechanical waves, Is the principle of superposition valid for waves that do not travel in the same plane ? For eg with one wave S1, travels along positive x-direction and another wave S2, is travelling in a direction inclined to the x-axis at an angle of 45 degrees (both the waves have same frequency and wavelength... |
To give context, suppose I have an uncharged and uniformly magnetized sphere with its magnetization in the $z$ direction with magnitude $M_0$. For this object, the volume bound current density $\mathbf{J}_b$ is obviously $0$, but it has a nonvanishing surface bound current density equal to$$\mathbf{K}_b=M_0\:\mathbf{e}... |
The Marx generator was invented by Erwin Marx in 1924 (1). This electric generator is an assembly of capacitors and spark-gaps. The capacitors charged in parallel and are discharged in serie. This device generates pulses of great power without having to design a high voltage capacitor.
The first attempts to obtain nucl... |
I know that this question has been repeated a lot. But I still don't understand this concept.
Big bang created matter and space but how could it possibly create time?
If Big bang didn't create time then Big bang must be a "POINT" in time.
Was Big bang the start of time?
Does time have a beginning? if yes, then is time ... |
Lets say we have a heat exchange unit which takes heat from a hot reservoir (a boiler) and dispenses heat to a radiator. I wonder about entropy balance:
Heat amount Q flows through from left to right.
What about entropy?
$S_1 = Q/T_1$ is taken from the left
$S_2 = Q/T_2$ is given to the right
So there is a net entropy... |
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