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88587 | Why doesn't static friction decelerate a rolling body? | I know that static friction isn't the cause of deceleration of a rolling body. But if static friction is the only force in the horizontal direction, then shouldn't there be some acceleration produced in this direction? The body should decelerate or accelerate. So how come in this case, a force does not produce accelera... | A solid sphere of mass \( m \) and radius \( r \) rolls without slipping down a ramp inclined at an angle \( \theta \) with respect to the horizontal. If the coefficient of static friction between the sphere and the ramp is \( \mu_s \), what is the maximum angle \( \theta_{\text{max}} \) at which the sphere can roll wi... | 16,155 | cqadupstack-physics |
19139 | How to distinguish female and male voices via Fourier analysis? | What makes one, without looking, be able to identify the gender of the talker as male or female? I mean if we Fourier analysed the voice of males and females, how the 2 spectrums are different which account for that distinction in sounds? | What are the key differences in the frequency components of male and female voices when analyzed using Fourier transformation, and how do these differences contribute to our ability to identify the gender of a talker just by their voice? | 3,034 | cqadupstack-physics |
7906 | How might a resonant antenna and black body radiation interact? | How does an antenna behave when it is cooled so that its black-body radiation is emitting energy at its resonant frequency? Edit: To clarify, its not how they're related in general, but how might thermal radiation and resonance interact with each other when their spectra are aligned well? Edit: Also, I'm sure that the ... | What is the theoretical effect on the efficiency of an antenna when it is cooled to a temperature where its black-body radiation peak aligns with its resonant frequency, and how does this interaction affect the power emitted at that frequency compared to non-resonant conditions? | 34,529 | cqadupstack-physics |
70024 | What is the optimal diameter for the exhaust hole in a pressurized vessel to deliver highest acceleration ? | Imagine you have a sealed cylindrical vessel with a given radius with a compressed gas inside. Let's give some numbers, 5 cm radius and 100 atm pressure. You poke a hole in the vessel and the gas will flow out, propelling the vessel in the opposite direction with a given force. Intuition tells me that this force depend... | If you have a sealed cylindrical vessel with a 5 cm radius and it contains compressed gas at a pressure of 100 atm, what is the optimal diameter of a hole to create in the vessel for maximum acceleration of the vessel, assuming the pressure remains constant? | 7,975 | cqadupstack-physics |
40824 | Is water considered a substance with low friction or high friction? | Like, for example, rubber is a substance with high friction, as an object with neither high or low friction would easily stop on it, and wouldn't skid. Ice is considered an object with low friction, as an object with neither high or low friction wouldn't easily stop on it, and would skid. But, what about water? | How does the coefficient of friction for water compare to that of rubber and ice, and what implications does this have for objects moving across each surface? | 23,901 | cqadupstack-physics |
102669 | Cart on Ramp with Varying Acceleration | For a lab that I have to do, the teacher has given me a data table of the displacement of a cart on a ramp after successive intervals of time. I have used this data to derive the velocities and accelerations of the cart. This is all fine, the problem is that I am now being asked to find the angle of the ramp. I don't k... | Given the displacement data of a cart on a ramp and the varying accelerations of -1.68 m/s² and -1.72 m/s², how can I calculate the angle of the ramp assuming the only force acting on the cart is gravity? Use the average acceleration to determine the angle, and perform the necessary calculations to obtain a quantitativ... | 18,937 | cqadupstack-physics |
27264 | Renormalization of the R-charge? | In general I would like to know as to known or what is/are the standard references about R-charge renormalization in supersymmetric theories. When does it do so and what is expected or known to be interesting. * A little more specifically I want to know whether something is particularly special if the R-charge of the... | In the context of supersymmetric theories, what are the implications of the R-charge of a scalar chiral superfield flowing to values greater than 1/2 compared to it flowing to values less than 1/2? Specifically, what physical phenomena can be expected if the R-charge approaches zero asymptotically, particularly in rela... | 3,683 | cqadupstack-physics |
17513 | Imaginary angle on simple centrifugal problem | Say somebody is spinning a mass on a string with a period $T$ around. If $T$ is very big, the mass will describe a small circle around the person's waist. If $T$ is very small, the plane of movement should be around shoulder high, with the actual radius being the full length of the arm and string.  s and the length of the arm and string is \( R = 15 \) cm, what is the angle of equilibrium \( \theta \) in radians between the person's arm and the vertical? Additionally, explain the significance of an imaginary solution for \( \theta \) in the context of thi... | 26,804 | cqadupstack-physics |
57837 | continuity of the electric potential due to a surface charge | The Electric potential due to a charge distribution on a surface is : $\Phi \left ( x \right )=\int \frac{\sigma \left ( {x^{}}' \right )dx{}'}{\left \| x-x{}' \right \|}da$ I want to show that it's a continuous function everywhere. | Prove that the electric potential $\Phi(x)$, given by the integral $\Phi(x) = \int \frac{\sigma(x') dx'}{\|x - x'\|} da$, is a continuous function everywhere for a given surface charge density $\sigma$. What conditions must $\sigma$ satisfy to ensure this continuity? | 35,402 | cqadupstack-physics |
91550 | Transport theorem derivation question | I am trying to rigorously go through some fluid mechanics proofs and theorems. I am currently going through a proof related to the transport theorem and I am having trouble with a step. The steps in question are the following, first the variables are transformed according to: $$ \frac{d}{dt}\int_{W_t} \rho \mathbf{u} d... | In the context of the transport theorem, how is the material derivative of the product of density and velocity, given by \( \frac{D}{Dt}(\rho \mathbf{u}) \), equal to the partial derivative with respect to time plus the convective term? Specifically, what is the mathematical justification for the equality \( \frac{\par... | 31,356 | cqadupstack-physics |
48512 | Speed of sound in air | Quick question. I thought that the speed of sound in air was constant, say in the right conditions of pressure and temperature, and humidity... 300 m/s. Now, if I have a sound source that moves towards me at 50 m/s, is the speed of the sound waves 350 m/s when it arrives to me? (this is not about the Doppler effect, wh... | If a sound source is moving towards an observer at 50 m/s, and the speed of sound in air is 300 m/s, what is the speed of the sound waves relative to the observer when they reach them? | 26,549 | cqadupstack-physics |
3967 | Can Loop Quantum Gravity connect in any way with string theory? | The one difficulty I see with LQG is that it requires an enormous number of degrees of freedom, _e.g._ these spin variables in the net. This is in contrast to stringy holographic theory where the fields in a space are equivalent to fields on a boundary or a horizon of one dimension lower. In this setting entropy of a b... | What is the relationship between entanglement entropy in string-brane theory and the degrees of freedom required in loop quantum gravity (LQG), particularly in terms of how they might both account for black hole entropy? | 2,942 | cqadupstack-physics |
55186 | Why is it called "annihilation"? | The term "annihilate" literally means "turn into nothing". However, when a particle and antiparticle collide, they clearly do not turn into _nothing_ ; they simply transform into different particles. Did the term originate at a time when physicists thought that matter + antimatter really did turn into nothing? Does any... | When an electron and a positron collide, they can annihilate and produce two photons. If the rest mass of an electron (or positron) is approximately 9.11 × 10^-31 kg, how much energy is released in this process, assuming that all the mass is converted to energy according to Einstein's equation \(E=mc^2\)? (Use \(c = 3.... | 18,832 | cqadupstack-physics |
28505 | How do I construct the $SU(2)$ representation of the Lorentz Group using $SU(2)\times SU(2)\sim SO(3,1)$ ? | This question is based on problem II.3.1 in Anthony Zee's book Quantum Field Theory in a Nutshell (I'm reading this for fun- it isn't a homework problem.) > Show, by explicit calculation, that $(1/2,1/2)$ is the Lorentz Vector. I see that the generators of SU(2) are the Pauli Matrices and the generators of SO(3,1)is a ... | How many distinct elements are there in the $(1/2, 1/2)$ representation of the Lorentz group, and how does this relate to the dimensionality of Lorentz transformations in spacetime? | 12,028 | cqadupstack-physics |
16349 | Why does an octave on a piano have the divisions of 8 white keys and 5 black keys? | An octave corresponds to a doubling or halving of the frequency. Each octave on a piano and in classical music score is broken downs into 8 white keys and 5 black keys. Is there a physics explanation for that division? | What is the total number of keys in an octave on a piano, and how does the arrangement of these keys relate to the frequency doubling or halving characteristic of musical octaves? | 16,090 | cqadupstack-physics |
82352 | LC Oscillator and relativity | There are two identical LC oscillators with electronic counters attached indicating how many times they have oscillated (from the time they are turned on). They are turned on simultaneously and one is kept on earth and other one is hurled to outer space at very large speeds on a rocket and brought back to earth after t... | If two identical LC oscillators are turned on simultaneously, with one remaining on Earth and the other being hurled into space at a significant fraction of the speed of light, what will be the difference in the oscillation counts displayed by the two oscillators when they reunite on Earth, according to the principles ... | 37,519 | cqadupstack-physics |
56483 | Eigenfunctions in periodic potential | For Hamiltonian $\operatorname H$ and lattice translation operator $\operatorname T$, if $$\operatorname H\psi=E\psi, \qquad \operatorname T\psi=e^{ik\cdot R}\psi,$$ and $$\operatorname H\phi=E\phi, \qquad\operatorname T\phi=e^{ik\cdot R}\phi,$$ then $\psi=\phi$? Here $R$ is lattice vector, $\psi$ can be $\psi_k$ and $... | Given two wave functions $\psi$ and $\phi$ that satisfy the eigenvalue equations $\operatorname H\psi=E\psi$ and $\operatorname H\phi=E\phi$, along with the lattice translation relations $\operatorname T\psi=e^{ik\cdot R}\psi$ and $\operatorname T\phi=e^{ik\cdot R}\phi$, can you determine the condition under which $\ps... | 979 | cqadupstack-physics |
14377 | Learn QM algebraic formulations and interpretations | I have a good undergrad knowledge of quantum mechanics, and I'm interesting in reading up more about interpretation and in particular things related to how QM emerges algebraically from some reasonable real world assumptions. However I want to avoid the meticulous maths style and rather read something more meant for ph... | What are some intuitive resources or books on the interpretation of quantum mechanics that focus on how it emerges from real-world assumptions, while minimizing rigorous mathematical formalism? | 5,416 | cqadupstack-physics |
15404 | What was so surprising about accelerating cosmological expansion? | The 2011 Nobel Prize in Physics, as far as I understand, concerns the expanding universe -- galaxies moving away from each other at ever increasing speed (that's what I think I read in newspapers). Now, the idea of expanding universe is not new. What is the novelty in this study? What was unexpected in it? | What experimental evidence did the 2011 Nobel Prize-winning physicists provide to support the theory of the accelerating expansion of the universe, and how does this differ from previous understandings of galactic movement? | 22,325 | cqadupstack-physics |
89618 | Understanding Weinberg's soft-photon theorem | The soft-photon theorem is the following statement due to Weinberg: > Consider an amplitude ${\cal M}$ involving some incoming and some outgoing > particles. Now, consider the same amplitude with an additional soft-photon > ($\omega_{\text{photon}} \to 0$) coupled to one of the particles. Call this > amplitude ${\cal M... | What is the proportionality factor between the original amplitude \({\cal M}\) and the amplitude \({\cal M}'\) when an additional soft-photon is taken into account, and how does it demonstrate the universality of the coupling of soft-photons across different types of particles? Please derive the expression for this pro... | 32,699 | cqadupstack-physics |
93212 | Circular motion and time dilation | Einsteins' time paradox was shown when two atomic clocks were synchronized and one was sent in a super sonic plane and the other kept at rest. When the two where then checked it was shown that yes indeed the clock that took the plain trip had lost time when compared to the clock that was kept at rest. My question is wh... | If one atomic clock is placed inside a centrifuge and spun at very high speeds while another is kept at rest, how would the time measured by the spinning clock compare to the time measured by the stationary clock, and what factors determine the magnitude of any time dilation effects experienced? | 12,461 | cqadupstack-physics |
133394 | What does raising voltage do? | If I raise the voltage of a wire from 0V to 1000V and then to 5000V, am I merely packing it with more and more electrons (with those electrons being trapped there until they find a path off the wire)? | If the voltage of a wire is increased from 0V to 1000V and then to 5000V, what happens to the electric field strength in the wire, and how does this relate to the movement of electrons within the wire? | 33,893 | cqadupstack-physics |
79328 | Diffusion of gas in a liquid with changing pressure and solubility (chemical potential) | Modelling the diffusion of a gas dissolved in water in a vertical column of water, several meters deep. Also assuming the water is completely still, so only diffusion plays a role. (Actually a model of methane and oxygen diffusion in the water in peatlands.) Fick's law says that diffusion flux $J$ depends on the concen... | How would you modify Fick's law to incorporate the effects of hydrostatic pressure and temperature gradients on the diffusion of gases, specifically oxygen and methane, in water? Additionally, what equations would you use to calculate the chemical potentials of these gases under varying pressure and temperature conditi... | 4,563 | cqadupstack-physics |
118540 | Does a AAA battery have a dipole moment? | Does a AAA or D battery have an electric dipole moment? Why don't the opposite poles of two batteries attract each other like that of magnet's? | What is the electric dipole moment of a AAA or D battery, and how does this dipole moment compare to the behavior of magnetic poles in terms of attraction or repulsion? | 14,741 | cqadupstack-physics |
122368 | Why and how almost periodic series constitute the algebra of observable of integrable systems? | In the introduction of his book _Noncommutative Geometry,_ p. 42, Connes explains that when a classical dynamical system has enough constants of motions, the motion of the system is almost periodic, and the algebra of observables is the algebra of almost periodic series $$q(t) = \sum q_{n_1 \dots n_k} \, \exp( 2 \pi i ... | What is the relationship between the number of constants of motion in a classical dynamical system and the algebra of observables being represented by almost periodic series, specifically in the context of the Arnold-Liouville theorem? | 23,674 | cqadupstack-physics |
54917 | Surely space-time Curvature does not explain gravity, it just describe its effects? | In special relativity co-moving objects see the other's 4-velocity as being only temporal. When they move relative to each other they see the other's 4-velocity has rotated so that it points less in the temporal direction but now has a spatial component. By the equivalence principle two co-moving objects falling toward... | How does the presence of mass as described by the energy-momentum tensor in General Relativity affect the geodesics or 4-velocity vectors of objects in free fall, and what implications does this have for our understanding of gravity as a fundamental force? | 28,429 | cqadupstack-physics |
48663 | Showing that position times momentum and energy times time have the same dimensions | I've been asked to show that both the position-momentum uncertainty principle and the energy-time uncertainty principle have the same units. I've never see a question of this type, so am I allowed to substitute the units into the expressions and then treat them as variables? If so, here's my attempt. Forgive me if I've... | Show that the position-momentum uncertainty principle and the energy-time uncertainty principle have the same units by substituting the appropriate units into their expressions and simplifying. What do you find when you compare the derived units for both principles? | 30,357 | cqadupstack-physics |
126755 | Position Representation in Quantum Mechanics | How does the 3d position operator look like in position representation? I know that in 1d the position operator $\hat{x}$ is just multiplication by $x$. | What is the mathematical form of the 3D position operator in position representation, and how does it differ from the 1D position operator, which is represented as multiplication by \( x \)? | 36,899 | cqadupstack-physics |
99462 | Global anomaly for discrete groups | We know that: > a global anomaly is a type of anomaly: in this particular case, it is a > quantum effect that invalidates a large gauge transformations that would > otherwise be preserved in the classical theory. I heard that from Wiki: > The adjective "global" refers to the properties of a group that are not > visible... | What is the relationship between discrete group symmetries and global anomalies, specifically: do all anomalies of a discrete group belong to the class of global anomalies, or is there any global anomaly that cannot be attributed to a discrete group? Additionally, can you provide specific examples of global anomalies a... | 28,985 | cqadupstack-physics |
100311 | Difference between horizon and flatness problems & how inflation solves flatness (w/out math) | Layman here so I'm hoping for an answer for my query that doesn't involve math. I'm reading about inflation and how it solves the flatness and horizon problems. I get that the horizon problem deals with the uniformity of matter/energy in the universe. Flatness deals with the curvature. But isn't the universe flat becau... | What is the critical density required for the universe to be flat, and how does it relate to the uniformity of matter and energy in the cosmological context? | 8,330 | cqadupstack-physics |
110905 | Electric Potential Change | Imagine we have a conductor in the shape of a sphere with charge $Q$ on it. The conductor is not grounded. There is an associated potential $V=\frac{Q}{4\pi\epsilon_0 R}$ at and in the sphere, where $R$ is the radius of the sphere. If we now deform the spherical conductor into some other shape, e.g. an ellipsoid (or di... | If a non-grounded spherical conductor with charge \( Q \) and radius \( R \) has a potential \( V = \frac{Q}{4\pi\epsilon_0 R} \), how does deforming it into an ellipsoid (while keeping the volume constant) affect its electrostatic potential? Provide a theoretical explanation for your answer. | 22,228 | cqadupstack-physics |
16034 | Tear drop shape | i heard that a tear drop shap is the most aerodynamic shape possible or the best is this true? If this isn't true what is since i need to make a fast ROV? Also since i need to have a propeller to propel it should it be on the front or back to produce the most thrust and the best hydrodynamcics? | What is the most aerodynamically efficient shape for minimizing drag in an ROV design, and how does the placement of the propeller (front vs. back) affect thrust and hydrodynamics? | 34,487 | cqadupstack-physics |
30918 | M-theory no lagrangian? | Is there any formulated lagrangian (density) for M-theory? If not, why is there no lagrangian? If not, is this related to many vacua existing? Thnx. | What are the implications of the absence of a formulated Lagrangian density for M-theory on the landscape of string theory vacua, and how does this absence relate to the number of distinct vacua that might exist? | 16,552 | cqadupstack-physics |
45331 | How to calculate the supporting force for a cantilever beam? | How do I find the supporting force $R_A$ and the moment $M_A$? Should I use the sum of moments or? | Given a beam supported at two points with a load applied at its center, calculate the supporting force \( R_A \) at point A and the moment \( M_A \) about point A. Use the sum of moments and the equilibrium conditions to derive your answers. If the total load is 200 N and the distances from point A to the load and from... | 31,093 | cqadupstack-physics |
57706 | Charge residing on an overpolished surface | I had very well read that when charge is stored on a rough surface, the leakage is very high from the pointed tips of such surfaces, by a phenomenon called action of points. But now, I've come to know that if a surface is over- polished (or say ideally polished), it becomes very difficult to store charge on it. I'm con... | Why does over-polishing a surface make it difficult to store electric charge, and how does this relate to the action of points and the dielectric properties of the surface? | 26,907 | cqadupstack-physics |
25577 | Stability of moons around tidally locked exoplanets | Can someone send me pointers to work (either theoretical or simulations) showing (in)stability of satellite orbits around tidally locked exoplanets? I want to know firstly if satellite orbits can survive the inward migration and secondly if once the planet becomes tidally locked if that has any implications for the orb... | What are the stability conditions for satellite orbits around tidally locked exoplanets, specifically focusing on earth-sized moons orbiting gas giants within the habitable zone, and how do tidal interactions from the host star affect these orbits? | 15,930 | cqadupstack-physics |
70562 | Movie airplanes and suction | Having watched a recent action movie (with zombies in it) I wondered whether the suction from a hole in the airplane's hull would really be able to rip out luggage, persons and even seating benches. To my understanding, "suction" is nothing but the lack of pressure, i.e. the suction in the airplanes cabin can only be p... | If a hole were to suddenly appear in an airplane's hull at cruising altitude, how much force would the differential pressure exert on objects such as luggage and seats inside the cabin, and would this force be sufficient to displace those objects out of the airplane? Please consider the cabin pressure, outside atmosphe... | 29,824 | cqadupstack-physics |
106151 | Gravity of very distant objects | As far as I know stars emit a finite number of photons in all directions in a given period of time and as an observer goes further away he experiences less and less photons to the point where the photon sphere is so spread out that sometimes he will not experience any photons making the star appear to be blinking. So m... | If a star emits photons uniformly in all directions at a rate of \( N \) photons per second, how many photons would an observer receive if they are located at a distance \( d \) from the star, given that the intensity of the light diminishes with the square of the distance? Assume that the area of the spherical surface... | 36,327 | cqadupstack-physics |
39303 | Are there experiments that are banned from being done at the LHC? | Are there experiments that are banned from being done at the LHC because they are too dangerous? | What specific experiments or particle collisions are considered too dangerous to conduct at the Large Hadron Collider (LHC), and what are the scientific reasons behind these restrictions? | 4,814 | cqadupstack-physics |
59999 | Work done by gravity on Water |  Now according to me we would see change in potential energy of system and equate it to the work done by gravity. But when we see this the first column lowers by $H/2$ and right one rises by $H/2$ and thus there should be no net work done. But it's not ... | In a system where one side lowers by \( H/2 \) and the opposite side rises by \( H/2 \), how can you calculate the total work done by gravity, and what specific factors might contribute to the positive net work done, despite the apparent equal displacement in opposite directions? | 13,957 | cqadupstack-physics |
107632 | quadrupole moment and higher for simple current loop | I'm working on a field configuration that needs to die off rapidly and I got to a $1/r^5$ dependence with canceling the dipole moment of the system cleverly, but to go get better arrangements I need to figure out the higher order moments of a simple loop as well. Griffiths (page 243, 3rd ed) refers to this integral $\o... | How can I evaluate the integral $\oint (r')^{n} P_n(\cos \theta ') dL'$ for a circular loop in order to determine the higher-order multipole moments, and are there known results or simplifications for these moments? | 5,230 | cqadupstack-physics |
48588 | Who are "we", and what counts as a "question" in consistent histories? | If the preferred basis in quantum mechanics and/or choice of consistent histories in consistent histories is arbitrary, and can only be determined by the "questions we ask", just who exactly is this nebulous "we", and what counts or doesn't count as a "question"? This is a _dead_ serious question. PS: Suppose we are cl... | In a closed quantum simulation scenario, if we pose a question before being "uncomputed" by the programmer/sysadmin gods, what is the probability that the information related to our question is retained after the simulation is terminated, considering that no external observation or measurement occurs? | 22,524 | cqadupstack-physics |
32257 | Magnet and energy conservation | If we consider a steel ball falling under gravity in a cup (potential well) and being stopped at the bottom by an obstacle then energy conservation implies that the gravitational potential energy has first been transformed into kinetic energy and then in heat. After the experiment the potentiel well's height is decreas... | How can we calculate the change in energy of a system comprising a magnet and a steel ball after they stick together, taking into account both the energy lost as heat and any changes in the magnetic moment of the magnet and the induced magnetic moment of the steel ball? | 2,003 | cqadupstack-physics |
102685 | Building a magnetron powered steamer | I am wanting to build a microwave powered steamer for a reverse engineering project in university. I've read up some on this and know that its not as efficient as a heating element. I'm curious about the wavelength changes of trying to heat a container of water directly with the magnetron. Unlike in a microwave which h... | What is the relationship between the size of a water container in a microwave steamer and the wavelength of microwaves, and how does this affect the efficiency of heating the water uniformly? Specifically, what dimensions would a container need to be within to minimize standing wave patterns and avoid overheating in on... | 2,654 | cqadupstack-physics |
113639 | What guarantees the existence of unitary operators implementing Lorentz Transformations? | This should be a very basic question. In introductory QFT books, often one of the first things we see is the following claim: for every Lorentz transformation $\Lambda$, we can associate an unitary operator $U(\Lambda)$ such that: $$ U(\Lambda)^{-1} \varphi(x) U(\Lambda)= \varphi(\Lambda^{-1}x)$$ And we also demand it ... | What are the necessary and sufficient conditions for the existence of a set of unitary operators \( U(\Lambda) \) that satisfy the transformation properties of an operator-valued quantum field \( \varphi(x) \) under Lorentz transformations, and can you provide an example of a quantum field for which such operators may ... | 28,061 | cqadupstack-physics |
60655 | Why uncertainity is minimum for coherent states? | While reading for quantum damped harmonic oscillator, I came across coherent states, and I asked my prof about them and he said me it is the state at which $\Delta x\Delta y$ is minimum. I didn't quite understand why it is minimum. Please explain why this happens? | What is the physical significance of the uncertainty relation for coherent states in a quantum damped harmonic oscillator, and can you explain why the product of uncertainties, \(\Delta x \Delta p\), is minimized in these states? | 616 | cqadupstack-physics |
92469 | Resonance force with multiple emitters | Will I get a stronger resonance if I put multiple frequency generators around the same object? example image | If two frequency generators are placed around the same object, generating frequencies of 100 Hz and 150 Hz, what is the resultant frequency experienced by the object, assuming constructive interference occurs? | 3,494 | cqadupstack-physics |
53819 | Calculating acceleration increase | ^ | | | | + | +| | + | | + | | + | | + | | + | | + | | + | | + | |+ | +---------... | If you have a concave curve representing acceleration as a function of distance and know the point x1 on the X-axis, how can you determine the maximum acceleration at x1 that allows you to reach this distance without exceeding it, assuming constant acceleration? | 9,046 | cqadupstack-physics |
128968 | How to measure trajectory regularity? | I have two animal running trajectories. A regular one with repeated back and forth running between point A and B, like the one on top in the figure. The other one is very irregular, animal paused and turned around a lot in the middle. Is there any algorithm to measure the regularity of a trajectory, like repeated activ... | Given two animal running trajectories over the same time period, one being a regular back-and-forth pattern between two points A and B, and the other being irregular with frequent pauses and turns, how can we quantitatively compare the regularity of these trajectories? Specifically, calculate the average speed, total d... | 3,355 | cqadupstack-physics |
21524 | A simple thought experiment about traversable wormholes | Let's say I have a tube, of large radius (about 5 - 7 meters in diameter), with traversable wormholes at the ends. The wormholes are arranged as such that if something falls inside one hole from inside of the tube, it will come out at the other end still inside the tube. Now, let's say I empty all air from the tube (to... | If a rock falls endlessly through a traversable wormhole in a vacuum tube that is 5-7 meters in diameter, how does its velocity change as it falls? Will the rock's mass increase due to relativistic effects, and is it possible for the rock to become massive enough to collapse into a singularity or to overpower Earth's g... | 1,254 | cqadupstack-physics |
101 | Production of antiproton at the Tevatron | The Tevatron is a proton-antiproton collider; it collides a beam of protons against a beam of antiproton. I can understand how we obtain the protons, but for the antiprotons ? How are they produced ? | How are antiprotons produced for collision in a proton-antiproton collider like the Tevatron? | 9,677 | cqadupstack-physics |
115161 | Lagrangian point or dark matter? | We know that spiral galaxies spin in a way such that we have to assume that dark matter is responsible for the extra mass required to do so. My question is, can Lagrangian points (L1 and L2) be used to describe a galaxy's rotation instead? Can we explain that objects far away from the center of the galaxy have higher v... | Can we calculate the orbital velocity of an object located at the L2 Lagrangian point in a galaxy, given the mass of the supermassive black hole at the galaxy's center and the mass distribution of the spiral arms? What would be the relationship between this velocity and the observed velocities of stars in the outer reg... | 13,271 | cqadupstack-physics |
131484 | Mixing mild and cold water, which one to pour first? | Suppose for example that a person like me likes his water in-between. A bit colder than the room temperature but not very cold. If you have a water dispenser that pours rtp water and cold water, which one to pour in the cup first to ensure the temperature I'm looking for? I was just thinking of it as I was pouring wate... | If a person prefers their water to be at a temperature just above room temperature (approximately 25°C), and has access to a water dispenser that dispenses cold water at 5°C and room temperature water at 25°C, what ratio of cold water to room temperature water should they mix in order to achieve a final temperature of ... | 24,161 | cqadupstack-physics |
128767 | Will an electron gun fire behind it? | If an electron travels as a wave, can it therefore not be aimed with any precision? If you fire an electron gun, can't you aim it at a particular slit? If the electron travels as a wave, will an electron gun hit anything at a 180 degree angle from the barrel? 360 degrees? | What is the probability of detecting an electron at a specific location on a screen when it passes through a double-slit arrangement, assuming it behaves as a wave? | 22,086 | cqadupstack-physics |
126101 | Finding the electric field strength of a collection of points | So I'm reading a text on electricity and it talks about using the integral to compute the total charge of a collection of points, which I mostly understand. But then we get to finding the electric field due to a charged collection of points and I find things that don't make sense to me. For instance, for an infinite sh... | Why is the electric field due to an infinite sheet of charge constant on one side of the sheet, and how does this differ from the electric field produced by a point charge, which decreases with distance? | 11,773 | cqadupstack-physics |
20558 | Nonablianity of Wilczek Zee Potential | Consider a hamiltonian with degeneracies of energy in parameter space $(R)$.Now the Geometric phase(Wilczek Zee Potential) will acquire a non abelian nature. To prove the non abelian nature of Wilczek Zee potential one generally take an unitary transformation of wave function $\psi(t)$ to $\Omega(t)\psi(t)$ and show th... | What are some alternative methods to demonstrate the non-abelian nature of the Wilczek-Zee potential, aside from using a unitary transformation of the wave function? | 37,556 | cqadupstack-physics |
61574 | Double- well potential and Mexican potential | Is double well potential related to Maxican hat potential? I have found on Quantum Field Theory in a Nutshell by A. Zee He wrote the double well potential as : $V (φ) = (λ/4)(φ^ 2 − v^2)^2$. Can anyone give me an argument for writing the equation like that. | What is the formulation of the double well potential in the context of quantum field theory, and how can it be expressed in terms of the Mexican hat potential? Please derive the relationship between the two potentials quantitatively. | 33,359 | cqadupstack-physics |
35736 | include the stretch of the spring own weight in potential energy for spring pendulum? | we are given a problem with spring with its own mass $m$. I am confused how to set up the PE term in the Lagrangian. Assume the spring has length of $L_{0}$ when it is laying on a table horizontally. Now when we hold the spring upright and hang it vertically from a pivot in the ceiling to make a pendulum, it will stret... | When modeling the potential energy (PE) of a spring pendulum of original length \( L_0 \) and mass \( m \), which expression for the PE is correct to include: \( PE = \frac{1}{2}k\left( y - L_0 \right) ^{2} - mg\frac{y}{2}\cos\theta - Mgy\cos\theta \) or \( PE = \frac{1}{2}k\left( y - \left( L_0 + \frac{(m/3)g}{k} \rig... | 8,305 | cqadupstack-physics |
37766 | Would string theory change everything? | Whilst I don't know anything except the definition of String theory and I'm a beginner, I'm curious about it. What I would like to know is: does string theory change a lot in Physics? If it's not true, what else would suffocate in Physics due to String theory? It's just an assumption and not some experimental observati... | What are the key experimental predictions of string theory, and how do they compare to those of established physical theories, such as quantum mechanics or general relativity? | 15,641 | cqadupstack-physics |
34741 | Equivalent definitions of primary fields in CFT | I have come across two similar definitions of primary fields in conformal field theory. Depending on what I am doing each definition has its own usefulness. I expect both definitions to be compatible but I can't seem to be able to show it. By compatible I mean definition 1 $\iff$ definition 2. I will write both definit... | Can you demonstrate the equivalence between the two definitions of primary fields in conformal field theory by showing that the transformation properties of the field \( f(z) \) under conformal transformations lead to the same conclusion for both definitions? Specifically, can you verify that definition 1 \( \iff \) de... | 11,093 | cqadupstack-physics |
68668 | What is the domain of validity of the Omega equation? | The Omega eqation is used in meteorology for estimate the value of the vertical velocity. Considering that the horizontal velocity field and density is given by observation. Under which condition this equation can be used for recover the vertical velocity and what is order of error between the real vertical velocity fi... | What conditions must be met for the Omega equation to accurately estimate vertical velocity in meteorology, and what is the maximum expected error between the actual vertical velocity and the value calculated using the Omega equation? | 32,822 | cqadupstack-physics |
1380 | Teleportation by quantum isolation | This is a thought experiment, so please don't treat it too harsh :-) Short: If we could isolate two places A and B in the universe from all and any interaction with the surroundings, is there a physical law which states "if something is dropped in place A, it has to stay there"? Long version: Let's assume that the ener... | If an object is placed in a perfectly isolated 1m³ box in the center of a planet, with no interactions with the outside universe, what physical principles govern its behavior over time? Would the object remain in the box indefinitely, or could it exhibit any changes in position or state, and why? | 24,434 | cqadupstack-physics |
77809 | Schwarzschild metric in a different coordinate system | In PADMANABHAN, Gravitation (Foundations and Frontiers), Cambridge, p $304$, exercice $7.6$, an example of the Schwarzschild metric in a different coordinate system is given : $$\mbox{d}s^2= -c^2\mbox{d}T^2 + \dfrac{4}{9}\left(\frac{9GM}{2(R-cT)}\right)^ {\large \frac{2}{3}} \mbox{d} R^2+\left(\frac{9GM}{2}(R-cT)^2\rig... | Given the Schwarzschild metric in a different coordinate system as defined by the equation
$$\mbox{d}s^2= -c^2\mbox{d}T^2 + \dfrac{4}{9}\left(\frac{9GM}{2(R-cT)}\right)^{\frac{2}{3}} \mbox{d} R^2+\left(\frac{9GM}{2}(R-cT)^2\right)^{\frac{2}{3}} \mbox{d}\Omega^2,$$
what is the relationship between the proper time $T$... | 38,303 | cqadupstack-physics |
108896 | Is there a general term for the situation where an improperly chosen measurement range results in a bias? | For example, consider the following measurement: A sensor can measure a specific physical quantity, and has a range of $0$ to $100$. All values above $100$ will be shown as 100. We now take the following measurements: $78$, $100$, $82$, $94$, $100$, and we conclude that the average is $90.8$. However, the true values w... | Given the true measurements of $78$, $112$, $92$, $94$, and $105$, calculate the true average value of these measurements. How does this average compare to the average reported by the sensor, and what does this discrepancy suggest about the concept of saturation in measurement systems? | 27,778 | cqadupstack-physics |
21704 | Do the trigonometric functions preserve units? | I saw an exercise where you had to calculate the units of $C_i, i=1,2$ from an equation like this: * $v^2=2\cdot C_1x$ and * $x=C_1\cdot \cos(C_2\cdot t)$ where * $x$ means _meters_ , * $t$ means seconds and * $v$ means velocity. For $C_1$ I got $C_1=m/s^2$. But coming to $C_2$ the cosinus irritates me someho... | If \( x = C_1 \cdot \cos(C_2 \cdot t) \) and \( x \) represents distance in meters while \( t \) is time in seconds, what are the units of the constants \( C_1 \) and \( C_2 \)? | 20,120 | cqadupstack-physics |
112304 | Electric Field Homework Question | Can a charged particle move through an electric field that exerts no force on it? | If a charged particle is placed in a uniform electric field where the electric field strength is zero, what is the net force acting on the particle, and can it still move? | 3,197 | cqadupstack-physics |
122917 | Can a point source be located more accurately out-of-focus or in-focus? | Let's say I am taking a picture, and I know _a priori_ that the image is of a single ideal point source of light at infinity. With a perfect imaging system **in focus** , the image shows an Airy disk. I already _knew_ to expect an Airy disk, so I can do some mathematical fitting to guess the center of the Airy disk. Th... | In an ideal imaging system capturing an image of a single point source of light, how does the accuracy of locating the source differ between using an in-focus image that displays an Airy disk and an out-of-focus image that appears as a larger blurry circle, considering factors such as pixel information and resolution l... | 31,802 | cqadupstack-physics |
15339 | Is it true that quantum mechanics technically allows anything to happen? | Maybe this is a silly question (I think it is), but it's a question I'm arguing with some of my friends for a long time. The ultimate question is: **Is everything (in our Universe) possible ?** I've read some books (Penrose, Hawking, Greene, etc.) where it was clearly stated several times that quantum mechanics allows ... | If a hypothetical scenario allows for any event to occur with an infinitesimally small probability, such as a Sun-sized star appearing in a person's pocket, what is the mathematical expression of the probability of this event occurring in terms of quantum mechanics? | 34,072 | cqadupstack-physics |
79307 | How can I weigh liquid in a sealed container? | How do you measure the mass and volume of alcohol if it is in a sealed container? Are there clever ways of achieving this? The weight of the container is not known. I can't open the container, I can't lose the alcohol inside, and I can't immerse it in water (as the label will break). | What methods can be used to calculate the mass and volume of alcohol in an airtight sealed container without opening it, submerging it in water, or weighing the container directly? | 34,586 | cqadupstack-physics |
17622 | curvature tensor component capable of doing work on $T_{\mu \nu}$ | I'm wondering what part of the curvature tensor is able to do work (and hence transfer energy) in matter. I'm wondering if this tensor: http://en.wikipedia.org/wiki/Stress-energy-momentum_pseudotensor satisfies that property I want to understand the generic assertion that GR doesn't conserve energy, and which scenarios... | In the context of General Relativity, how does the stress-energy momentum pseudotensor relate to the concept of energy conservation, and in which specific scenarios can energy be considered conserved in a gravitational field? | 12,629 | cqadupstack-physics |
29207 | The metric expansion of space and Hawking | In a Wikipedia article I read that the "Metric Expansion of Space" exceeds the speed of light. If this is true then we must be being disconnected from very remote parts of the universe since gravity can only travel at the speed of light. In his book "A Brief History of Time", Hawking seems to still believe in the big c... | If the metric expansion of space can exceed the speed of light, how does this affect the potential for gravitational interactions between distant galaxies, particularly in the context of theories like the big crunch? Could you quantify the distance at which galaxies would no longer be able to gravitationally influence ... | 30,143 | cqadupstack-physics |
75805 | A table of Particles and Energies In different satellite orbites(GEO MEO LEO) | I have done a bunch of search for information about: which particles with how much energy exist in near space environment of earth in inner and outer Van Allen Belt or satellite orbits like GEO MEO and LEO, and I found some sporadic and sometimes antithetic information. Any help Would be awarding. | What types of charged particles are most commonly found in the inner and outer Van Allen Belts, and what are their typical energy levels (in electron volts) in these regions? | 3,410 | cqadupstack-physics |
64320 | Expanding two-variable function $f(x,y)$ over the complete sets $\{ g_{i}(x) \}$ and $\{ h_{j}(y) \}$ | Quite often (see, for example, this PDF, 50 KB) when discussing the Born- Oppenheimer approximation the following assertion is made: any well-behaved function of two independent variables $f(x,y)$ can always be expanded over the complete set of functions $\\{ g_{i}(x) \\}$ and $\\{ h_{j}(y) \\}$ in the following way $$... | In the context of the Born-Oppenheimer approximation, can you explain how the function \( f(x,y) \) can be represented as a double sum \( f(x,y) = \sum\limits_{i} \sum\limits_{j} c_{ij} g_{i}(x) h_{j}(y) \) and under what conditions this decomposition holds true? Additionally, what mathematical principles or theorems s... | 10,934 | cqadupstack-physics |
127292 | Sound Wave out of phase | I connected my speakers to my sound system switching the +ve and -ve one of the speakers I can notice them beating out of phase but how come I don't hear any difference and at what position will it undergo destructive interference and the sound will be of 0 intensity ( I've never experienced it in real life so I'm gues... | When connecting two speakers in a sound system and reversing the polarity of one, how far apart must the speakers be in order to experience destructive interference at a specific frequency, resulting in an intensity of 0 dB at a given position? Consider a frequency of 440 Hz and calculate the distance required for this... | 481 | cqadupstack-physics |
99882 | How to prove that a spacetime is maximally symmetric? | In Carroll's book on general relativity, I found the following remark: > In two dimensions, finding that $R$ is a constant suffices to prove that the > space is maximally symmetric [...] In higher dimensions you have to work > harder Here, $R$ is the Ricci scalar. This begs the following questions: * How _does_ ones ... | What is the condition for a four-dimensional spacetime to be considered maximally symmetric, and how does the positivity of the Ricci scalar relate to this condition? | 29,217 | cqadupstack-physics |
45693 | How quarks converted into leptons |  Since the charged pions decay into two particles, a muon and a muon neutrino, seems quarks disappeared!, The decay proceeds by the weak interaction $W^{+}$ and can be visualized in terms of Feynman diagrams. Isn't it why Quarks ... | What are the quantum numbers of the particles produced in the decay of a charged pion (π⁺) into a muon (μ⁺) and a muon neutrino (νₘ), and how does this process illustrate the conservation laws in particle physics? | 14,959 | cqadupstack-physics |
33183 | Implementing a black-body using Planck's Law in a 3D ray tracer | **1_** In one of my software projects, I need to implement Planck's Law in terms of wavelength. I can't be sure if it's right because I've seen different variations of it, and all the implementations that I've tried give different results (besides, it's been years since I've had to do physics). Could someone verify tha... | If I calculate the spectral power distribution using Planck's Law for wavelengths ranging from 360 nm to 830 nm in increments of 5 nm at a temperature of 6504 K, what should the resulting XYZ colorimetric values be, and will they match the CIE Standard Illuminant D65? Please verify the calculations using the Planck's L... | 28,388 | cqadupstack-physics |
106058 | Water and electricity? Hot or Cold? | Is hot water or cold water more conductive for electricity or is it the same regardless? | How does the conductivity of hot water compare to that of cold water, and what factors influence any differences observed? | 13,654 | cqadupstack-physics |
33235 | Do particles gain mass only at energy levels found during the big bang? | I am trying to make sure my understanding is correct. At energies and temperatures found during the big bang (or at CERN recently), the Higgs mechanism comes into effect. When it does, there is a break in electroweak symmetry (because the field is unstable?) and a condensate is formed. This condensate is what allows bo... | At what temperature (in Kelvin) is it theorized that the Higgs mechanism became effective, leading to the electroweak symmetry breaking and the acquisition of mass by particles in the early universe? | 8,998 | cqadupstack-physics |
76517 | Relative weights in rotational bands of symmetric diatomic molecules | In an old paper, Ehrenfest 1931, the introduction starts off as follows: > The band spectra of symmetric diatomic molecules show certain striking > differences from those of asymmetric molecules. For when the two nuclei of > the molecule are identical, the intensity of the individual lines of a band, > instead of varyi... | In the context of molecular spectroscopy for symmetric diatomic molecules, if the degeneracy of the nuclear ground state is \( g \), how does the relative weight define the ratio of transition rates for odd and even rotational states \( J \) leading to observable intensity variations in the absorption spectra? Can you ... | 14,599 | cqadupstack-physics |
16059 | Can a super-extremal charged black hole be made out of electrons only? | In a previous Question it was argued that it would be impossible to add enough charge to a black hole to make it pass the extremal black hole limit since adding charge would increase the mass of the black hole due to the electrostatic field energy (and thus mass) that would be added as the charge is added. Note that an... | Can a sphere of electrons, uniformly distributed with a low charge density, be constructed such that its total charge causes it to form a super-extremal black hole, given that the Schwarzschild radius of the spherical mass would eventually exceed the initial radius of the sphere as it increases? Please provide a quanti... | 12,295 | cqadupstack-physics |
11995 | Defining Measurement in Quantum Mechanics | I should begin by saying that _I am a total newbie when it comes to Quantum Mechanics._ Therefore my question might sound metaphysical to people who know their stuff. So please forgive. What I am trying to understand is the basic system of an electron in a box. Suppose I place a detector at a fixed point inside and try... | In a one-dimensional infinite potential well (a "box"), if a detector placed within the box fails to detect an electron, how does this influence the wave function of the electron if the measurement is considered a valid event in the Copenhagen interpretation of quantum mechanics? Specifically, if the electron is subseq... | 16,125 | cqadupstack-physics |
32369 | Is there anything special about the Sun's photosphere in terms of density? | The Earth has a definite boundary between rocky/ watery surface and gaseous atmosphere. The same cannot be said of the sun. Even though the photosphere gives an apparent "edge" to the sun via the human eye, the matter of the sun continues on significantly further. I have even heard a claim that from a certain perspecti... | What is the general shape of the density profile of the sun as a function of distance from its center, and does this profile exhibit any discontinuities or unusual characteristics at the photosphere? | 16,393 | cqadupstack-physics |
133713 | Is the Higgs Boson a Force Carrier? | I am told there are four fundamental forces, and each of these forces has a boson that acts as its carrier. Reading this http://www.fnal.gov/pub/science/inquiring/questions/higgs_boson.html I find that the Higgs Field is not a force field > The Higgs field is not considered a force. It cannot accelerate particles, > it... | What is the relationship between the Higgs boson and the mass of different particles, and how does this influence our understanding of fundamental forces in physics? | 15,505 | cqadupstack-physics |
122933 | Will a blanket warm you if you are underwater? | Suppose a man falls into very cold water and gets their foot stuck under a heavy rock. Fortunately, his head is above water and someone is able to call for help. The paramedics want to keep him warm while they work on freeing his foot. They put a hat on his head. Should they also wrap him in a blanket? | What is the estimated heat loss from the man's body per minute into the cold water if the water temperature is 5°C and the man's initial body temperature is 37°C? Additionally, how does wrapping him in a blanket affect his heat retention in this scenario? | 32,004 | cqadupstack-physics |
121503 | Angular momentum for 3D harmonic oscillator in two different bases | I know that the energy eigenstates of the 3D quantum harmonic oscillator can be characterized by three quantum numbers: $$ | n_1,n_2,n_3\rangle$$ or, if solved in the spherical coordinate system: $$|N,l,m\rangle$$ The relationship between capital $N$ and the little $n_i$'s is straightforward: $N=n_1+n_2+n_3$, but this ... | If the energy of a 3D quantum harmonic oscillator is fixed at \(\frac{5\hbar \omega}{2}\), corresponding to \(N=1\) in the state representations \(|n_1,n_2,n_3\rangle\) and \(|N,l,m\rangle\), what are the allowed values of the quantum numbers \(l\) and \(m\) in the second representation, and what are the specific state... | 16,664 | cqadupstack-physics |
77758 | Two puzzles on the Projective Symmetry Group(PSG)? | Recently I'm studying PSG and I felt very puzzled about two statements appeared in Wen's paper. To present the questions clearly, imagine that we use the Shwinger-fermion $\mathbf{S}_i=\frac{1}{2}f_i^\dagger\mathbf{\sigma}f_i$ mean-field method to study the 2D spin-1/2 system, and get a mean-field Hamiltonian $H(\psi_i... | In a two-dimensional spin-1/2 system described by a mean-field Hamiltonian \( H(\psi_i) = \sum_{ij}(\psi_i^\dagger u_{ij}\psi_j+\psi_i^T \eta_{ij}\psi_j + H.c.) + \sum_i \psi_i^\dagger h_i \psi_i \), how can you verify that the projection \( P\widetilde{\Psi} \propto P\Psi \) for mean-field ground states \( \Psi \) and... | 9,442 | cqadupstack-physics |
135047 | Moment of inertia as a tensor | A professor at my university briefly stated that moment of inertia is a tensor and can be represented by a $3×3$ matrix. I don't have a good idea of what a tensor is, so I would be grateful if someone could explain how to **intuitively** think of moment of inertia as a tensor. | How can the moment of inertia be represented by a \(3 \times 3\) matrix, and what physical interpretation does this matrix provide regarding rotational motion about different axes? Additionally, can you calculate the moment of inertia tensor for a solid cylinder of radius \(R\) and height \(h\) about its central axis? | 3,263 | cqadupstack-physics |
23364 | Units describing the behavior of neutrinos | http://proj-cngs.web.cern.ch/proj-cngs/Download/CNGSDGVE/cngsdgve.pdf on page 13 I read that "the present plan is to provide nu_mu neutrinos with an energy between 5 and 30 GeV." Wikipedia neutrino article https://en.wikipedia.org/wiki/Neutrino says that neutrinos are electrically neutral. What is the justification of ... | What is the range of energy in GeV that muon neutrinos (νμ) are planned to be provided in current experiments, and how does this energy range support the study of neutrino interactions? | 13,733 | cqadupstack-physics |
86432 | Electrodynamics and induced EMF question | > A very long straight wire carries a current I. A plane rectangular coil of > high resistance, with sides of length $a$ and $b$, is coplanar with the > wire. One of the sides of length $a$ is parallel to the wire and a distance > $D$ from it; the opposite side is further from the wire. The coil is moving > at a speed ... | A long straight wire carries a constant current \( I \). A rectangular coil of high resistance, with sides of length \( a \) and \( b \), is moving away from the wire with speed \( v \). The side of length \( a \) is parallel to the wire and at a distance \( D \) from it.
(a) Calculate the electromotive force (e.m.f.... | 618 | cqadupstack-physics |
129069 | Naive questions on the concept of effective Lagrangian and equations of motion? | Let us consider a LC circuit containing an electric dipole moment, the **quantum** system (electric field $E$ coupled with a dipole moment) can be described by the path integral $$Z=\int DEDxe^{i\int dtL},$$ where the total Lagrangian $$L=\frac{1}{2g}(\dot{E}^2-\omega _{LC}^2E^2)+\frac{m}{2}\dot{x}^2-\frac{m\omega _{0}... | Given the effective Lagrangian $$L_{eff}=\frac{1}{2g}(\dot{E}^2-\omega _{LC}^2E^2)+\frac{e^2}{2m}E(\partial_t^2+\omega _{0}^2)^{-1}E,$$ can you derive the Euler-Lagrange equation corresponding to $L_{eff}$, and compare it with the fourth order equation of motion $$[\partial_t^4+(\omega _{0}^2+\omega _{LC}^2)\partial_t^... | 5,712 | cqadupstack-physics |
95408 | A rod of charge? | Say you have a _finite_ rod of conducting charge. The field from one side of the rod looks like Figure 1:  At the centre of the sheet, the field lines are straight because of symmetry. (for an infinitesimal length of of the rod) (See Figure 2). Therefor... | If a finite conducting rod with uniform charge density is placed along the x-axis and a point charge is positioned at its center, how does the electric field strength at the position of the point charge change as you move away from the center along the perpendicular bisector of the rod, and what is the mathematical exp... | 36,806 | cqadupstack-physics |
21238 | Mechanism by which electric and magnetic fields interrelate | I read that force due to electric field on some particle in one reference frame can exhibit itself as force due to magnetic field in some other reference frame and that electric and magnetic fields are two aspects of same underlying electromagnetic field. My question is what is the mechanism which can explain how an el... | How does the motion of charged particles in a current-carrying wire relate to the generation of a magnetic field in a different reference frame, according to the principles of relativity? Can you explain this mechanism without delving into mathematical formalism? | 28,344 | cqadupstack-physics |
130368 | Faddeev-Popov Ghosts | When quantizing Yang-Mills theory, we introduce the ghosts as a way to gauge- fix the path integral and make sure that we "count" only one contribution from each gauge-orbit of the gauge field $A_\mu\,^a$, because physically only the orbits themselves correspond to distinct physical configurations whereas the motion wi... | In quantizing Yang-Mills theory, we introduce gauge-fixing for bosonic fields, but how is the gauge-fixing process for fermionic fields reconciled, given that both fields have gauge transformations and gauge orbits? Specifically, what is the determinant of the functional in the gauge-fixing term, and how does it ensure... | 7,990 | cqadupstack-physics |
127934 | Calculate the current in mA which will be flowing through the two resistors | Three resistors of 3,4 and 5 ohms are joined in parallel in an electric circuit. If a current of 150mA flows through the resistor of 4 ohms,then calculate the values of the current in mA which will be flowing through the other two resistors. I could not comprehend the question completely.Thanks in advance. | In a parallel circuit with resistors of 3, 4, and 5 ohms, if a current of 150 mA flows through the 4-ohm resistor, what are the currents flowing through the 3-ohm and 5-ohm resistors? | 21,866 | cqadupstack-physics |
130466 | Minkowski to Euclidean | When dealing with solutions to Einstein's equations given by a 4d metric with signature $(-,+,+,+)$, we're able to move to Euclidean space using some transformation so that our signature is now $(+,+,+,+)$ and our metric is changed slightly different. What I'm worried about is what this does to the properties of my met... | What are the implications for the properties of the metric \( V_1 \) when transitioning from the Lorentzian metric \( ds_1^2 \) to the Euclidean metric \( ds_2^2 \), given the condition that \( V_2(a=b) = 0 \) and that \( V_1(-i a=b) = 0 \) when \( a \), \( b \), and \( c \) are real parameters? Specifically, how does ... | 7,039 | cqadupstack-physics |
113217 | Proton-electron inability of annihilation | Why would an electron annihilate with a positron if it sees one nearby but would prefer to orbit the proton rather than annihilate with it, despite that the force of attraction being the same? | What is the average distance at which an electron is more likely to encounter and annihilate with a nearby positron compared to the distance at which it orbits a proton, given the electromagnetic force between them? | 29,590 | cqadupstack-physics |
59947 | Electric field at a point $P$ | > **Problem** > Charge is distributed uniformly over a large square of side $l$, as shown > in the figure. The charge per unit area ($C/m^2$) is $\sigma$. Determine the > electric field at a point $P$ a distance $z$ above the center of the plane, > in the limit that $z<<l$. > >  at a point \( P \) a distance \( z \) above the center of a uniformly charged square plane of side length \( l \) with surface charge density \( \sigma \). Assume the limit where \( z << l \). Additionally, evaluate the integral involved in the computation of \(... | 31,401 | cqadupstack-physics |
95288 | Are there any materials that change the electromagnetic wavelength of visible light? | What i mean is for example exclusively red light comes in but gets reflected or refracted as blue or xray wavelength or whatever. Does this happen at all? | Is it possible for a medium to absorb exclusively red light and then emit or transmit light of a different wavelength, such as blue or X-ray wavelengths? If so, what are the mechanisms behind this process and under what conditions does it occur? | 21,191 | cqadupstack-physics |
72213 | Potential energy: Electric field two spherical charges | I want to determine the potential energy of two equally charged spherical charges by using the equation: $V_{pot}= \int_V \frac{1}{2} \epsilon_0 E^2 dV$ and therefore I was wondering what I has to take as $E$? The sum of the electric fields of both charges? Notice, that I want to use this equation on purpose since it e... | Given two equally charged spherical charges, how would you calculate the potential energy within a specified volume using the equation \( V_{pot} = \int_V \frac{1}{2} \epsilon_0 E^2 dV \)? Specifically, what expression for the electric field \( E \) should you use to accurately represent the interaction between the two... | 22,471 | cqadupstack-physics |
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