All Questions

6
votes
2answers
70 views

What is the link between the rotating wave approximation and the algebraic representation of a dynamical system?

In analyzing a system of two coupled oscillators, I noticed a rather interesting correspondence between the so-called "rotating wave approximation" (RWA) for solving differential equations and the ...
-1
votes
2answers
48 views

Why can I not conserve kinetic energy in the following case? [on hold]

For the 2nd part of the question, if I conserve angular momentum about the centre of mass of the rod I get one value, and if I conserve kinetic energy of the rod and ball system before and after ...
0
votes
0answers
13 views

why a car with very high speed topples away from the center of turning when it is cornering? [duplicate]

If a car is turning to the right with very high speed, why the car will topple to the left and cause an accident?
1
vote
1answer
36 views

Where's the Database in Grover's Algorithm

I am a little confused by parts of Quantum Computation and Quantum Information by Nielsen and Chuang on Grover's algorithm: Grover's algorithm searches a number of quantum states for a "marked ...
0
votes
2answers
42 views

Why the quantities are dimensionless in curves plots?

In a lot of plots they use dimensionless quantities, why really we don't let quantities in their physical dimension and plot the curves normally.
0
votes
1answer
18 views
-3
votes
0answers
17 views
0
votes
1answer
34 views

Can a light absorbing bulb-like thing be made?

A bulb emits light. So can a bulb-like thing or anything be made such that it absorbs all/most of the light when turned on? For example, when room is dark we switch on bulb and it spreads light. Let ...
-2
votes
1answer
24 views

power calculation when subjected to certain load [on hold]

What is the power consumed by a battery whose voltage is $300$ V which has a capacity of $3000$ Ah? When it is pulling a load of $430$ tons at a speed of $10$ kph for a period of $10$ minutes. In ...
2
votes
4answers
48 views

Normal Force on an object on the earth’s surface

If a body is on the earth’s surface at equilibrium, the forces acting on it are gravitational (by the earth’s centre) and normal (by the surface). These balance each other and allow the body to ...
0
votes
1answer
31 views

Intensity pattern in a single-slit diffraction

In a single-slit diffraction, what happens to the intensity pattern if the slit width becomes narrower and narrower?
2
votes
2answers
79 views

What happens when the wavelength of light becomes as large as the observable universe? [on hold]

Say the wavelength of a photon became so large that it approached the size of the observational universe. Does something unexpected happen?
3
votes
2answers
86 views

Mathematical formulation of quantum mechanics

I am reading a book on quantum mechanics, but it is difficult to understand. Quantum mechanics is roughly formulated as follows: Physicsl state is a normalized ray $\{e^{i\theta}\psi|\theta \in \...
1
vote
2answers
54 views

Nature of motion between comoving observers; What is the common time that they agree on?

This is a set of follow-up questions regarding this post. The following four queries are very closely related and needed to asked at the same place. Question 1 Is it really possible to regard the ...
0
votes
1answer
41 views

Einstein's Theory of Relativity Time Dilation

My friend claims that this proves that time moves faster on a mountain than at sea level. He says that since both of these people start and end at the same angular position and are both traveling at ...
-1
votes
1answer
37 views

Is the magnetic force fully analogous to gravitation?

Superficially, the force between two magnets would seem to be fully analogous to gravity because each is the product of two factors divided by the square of the distance between the objects being ...
-1
votes
1answer
22 views

Combining two power sources to get voltage from one and current from another

For a project, I have to make a battery that output 5 V, 500 mA. However, each one of my cells can only produce 1 V, 80 mA. I can combine these cells in series and parallel to get the required ...
0
votes
1answer
38 views

What is “quantized momentum transfer”, and can it account for the double-slit experiment?

In https://www.sciencedirect.com/science/article/pii/S0378437109010401, the author claims that the interference pattern obtained in the double-slit experiment does not need a wave description of ...
2
votes
0answers
36 views

Prove from first principles that a guitar string will vibrate at a constant frequency

From experience I am aware that a taught string will generally vibrate with a constant frequency. I wanted to prove this by considering the relation of distance from the resting position, and its ...
1
vote
1answer
28 views

When is emitting a particle (e.g. neutrino) the same as absorbing an antiparticle?

I've read that Pauli first proposed the neutrino to explain energy and momentum conservation in this equation: $$n \to p^+ + e^- + \overline\nu_e$$ But it is also written differently here: $$\nu_e ...
0
votes
0answers
14 views

Are neutrinos or antineutrinos more prevalent?

As I understand it, neutrinos were first proposed to explain energy and momentum conservation in beta decay, as a hypothetical particle emitted together with the electron and proton. Thus Pauli gave ...
4
votes
2answers
2k views

What happens when the centripetal force is equal and opposite to the centrifugal force? [duplicate]

We say that centrifugal force is fictitious, yet we still use it in some problems. If the centrifugal force is equal and opposite to the centripetal force wouldn't that make the net force zero?
3
votes
1answer
55 views

Why are angular velocity and angular frequency not measured in Hertz?

Recently, I was doing my homework and I found out that Angular Velocity and Angular Frequency can be calculated using $\omega=v/r$. This means the units of torque are (meter/second)/meter or 1/second. ...
2
votes
1answer
49 views

Why is $\chi_{[\mu}\nabla_\nu \chi_{\sigma ]} = 0$ at the Killing horizon?

Let $\chi$ be a Killing vector field that is null along a Killing horizon $\Sigma$ Why is $\chi_{[\mu}\nabla_\nu \chi_{\sigma ]} = 0$ at $\Sigma$?
0
votes
0answers
10 views

How many combinations of physical constants would allow a sustainable/similar universe? [on hold]

If physical constants like the gravitational constant, the speed of light, charge/mass/spin of an electron, etc, were to be different, how different could they be while still producing a universe ...
0
votes
0answers
46 views

Can wave collapse during measurement be avoided with a better experiment / measurement apparatus?

Or to restate the question, does quantum mechanics or the quantum field theory state or imply that we can only observe the wave in a collapsed state? And if they don't, do we have any promising ...
0
votes
0answers
28 views

In the Joule-Thomson experiment, how is $T_1-T_2$ determined?

I figured out that $H = U +pV$ is constant in this adiabatic condition. I am confused about the expression "$T_1-T_2$ is determined in this condition". I don't think it's an ideal gas, so $\delta(H) \...
0
votes
0answers
21 views

Potential Flow integration (no-voice and very beginner!)

Let's say I managed to compute a velocity field that is divergence-free. How do I integrate it over time? meaning, I created a potential function, set v to be curl of potential function, so I have now ...
0
votes
1answer
63 views

What would the effects be on the world if light slowed down? [duplicate]

It would be really helpful if the effects were just given in a list form so I can research them. The reason why I am asking this is because I to write an essay regarding the effects of a change in a ...
-1
votes
1answer
52 views

Physics theory/concept behind this question [on hold]

The question is: Two cars start off at the same location and move away at constant velocities. At $t = 0 s$ car $A$ moves away with a velocity of $12.5 m s^{−1}$ NORTH and car $B$ moves away with a ...
1
vote
1answer
40 views

Can Mars have an oxygen atmosphere?

It is my understanding that, in its gaseous state, oxygen molecules move fast enough to achieve escape velocity. On Earth, we see this more clearly with helium. Regardless of what's happening on ...
1
vote
1answer
48 views

Why parity required symmetry?

I'm studying parity for the first time but there is something I don't understand. I read that a system conserves parity if every experiment is the same in a mirror that is also $180^{\circ}$ flipped. ...
0
votes
1answer
41 views

How to Construct Proper Spherical Coordinates in Minkowski Spacetime?

In $n$ dimensional Euclidean space, we only need one radial coordinate, and $n-1$ angular coordinates, where one ranges from $[0, 2π)$ and the rest range from $[0, π]$ Spherical Minkowski coordinates ...
2
votes
1answer
65 views

Problems of Klein Gordon equation

Consider the Klein-Gordon equation $$(\square+m^2)\varphi=0.$$ People usually claim that $\varphi^* \varphi$ cannot be interpreted as a probability density because $\int d^3\vec{x}\varphi(t,\vec{x})^*...
0
votes
0answers
20 views

How much more damage is caused after hitting a brick wall at 100mph over 50mph? [duplicate]

How much more damage is caused after hitting a wall at 100mph over 50mph? It is clear that there is just twice as much force generated after hitting a wall at 100mph, since the deacceleration is twice ...
1
vote
0answers
34 views

Does Graviton bend light?

In the weak gravitational regime where the low-energy effective action holds,(linearized) gravity can be quantized, and we can treat graviton as quantum fields on a Minkowski background. One can also ...
0
votes
1answer
23 views

What is the relation between Reflectance and Intensity?

I am just reviewing Fresnel's equations where Reflectance $R$ is equal to $$R=|r|^2$$ where $r$ is the complex reflection coefficient. Is there an equation that relates $R$ to intensity or is there ...
0
votes
0answers
25 views

Moving a (specific)-spacecraft without ejecting mass [on hold]

The idea is to move this spacecraft without ejecting any mass. The craft has two paddles which we can make spin. So we rev these two paddles up, spinning them in opposite directions and when their ...
0
votes
0answers
20 views

What devices are used in a proton accelerator to separate the protons from their electrons and send the protons into the vacuum chamber?

I understand the general idea of how they accelerate the protons once they get them isolated in the chamber, but what's the device they use to isolate them to begin with even called?
0
votes
1answer
27 views

Prove that the electric field produce by a punctual charge is isotropic and radial

I would like to prove mathematically that the electric field produced by a punctual charge is isotropic and radial, i.e. $$\vec{E}(r,\phi,\theta)=E(r)\vec{e}_r\tag{1}$$ I think that this statement ...
0
votes
0answers
11 views

Density of states analogue in non-interacting multi-electron atom

I'm reading a paper on optical effects which very early on assumes that there are no interactions. Given that I want to simulate an atomic vapour (modeled, initially, at least, as non-interacting ...
-10
votes
0answers
49 views

QM1223344556666664545 [on hold]

Schrödinger's electron electric wave replaced with an electron probability wave but an electron position probability can only represent a positive value or zero and cannot depict a negative value that ...
0
votes
2answers
54 views

Why does current always go to the resistance which is lower? [duplicate]

Why does current chose the easy way? Is there a proper mathematical formula about why current tends to go over a resistance which is smaller?
1
vote
0answers
16 views

Relative velocity and pseudo forces

If I am in a spaceship moving in deep space....... which is accelerating.... There is nothing around to compare my motion with.... How can I say even if I'm moving or not....if I say I experience a ...
0
votes
0answers
20 views

Can electrical currents be accelerated due to the geometry of the conductor?

If dc current is passed through a section of piping to detect discontinuities, can certain flaw geometry (cracking, porosity) cause an decrease in resistance?
0
votes
1answer
31 views

Luminosity of a white dwarf

I have a very simple question, yet i am confused.Can someone tell me why in an H-R diagram the white dwarfs are at the bottom left? As in I understand that they would have a high temperature when they ...
0
votes
0answers
11 views

Determining the position and spectral weight of Andreev states from a retarded Green Function

I'm trying to understand a result from the paper Josephson current through a correlated quantum level: Andreev states and $\pi$ junction behavior by Vecino, Martin-Rodero and Yetati (2003). ArXiv link ...
0
votes
0answers
5 views

How to add protective enclosure around exposed thermal camera

First off, let me state that I'm not entirely sure this is the right forum for this question. This was the only section I found multiple questions pertaining to thermal imaging, however, so I thought ...
1
vote
1answer
44 views

Wigner map of the product of two operators

Does anyone know how to prove that for the product of two operators $\hat{A}\hat{B}$ the Weyl-Wigner correspondence reads $$ (AB)(x,p) = A\left (x-\frac{\hbar}{2i}\frac{\partial}{\partial p}, p+\frac{\...
0
votes
2answers
45 views

Why does current remain same in a series circuit?

Current is the rate of flow of charges with time. When passing through each resistance in a series circuit, charges lose energy and "slow" down due to collisions with atoms (metal cations). When time ...

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