# All Questions

1answer
92 views

### How to calculate precipitation chance with basic weather data?

I would like to know if there is any algorithm which allows us to calulate precipation chance with following data: temperature, humidity, illuminance (in lux) and pressure. I've searched it in google, ...
0answers
20 views

### Imaginary time formalism

Consider a function of energy-scale $\tilde{F}(k)$ and its fourier transform in time as $F(t)$ (as energy-scale is the fourier-conjugate of time in Minkowski space). Then we have ...
1answer
43 views

### Do wormholes violate causality [duplicate]

Does opening and closign a wormhole to send a message within seconds across the galaxy violate causality? Wouldn't different observers disagree about the order of events and what effected what? Is ...
1answer
13 views

### Dynamic response of temperature change when identical fluids flowing mix together

As shown in the below figure , there is a mixing of a fuel in a system. the mass flow rates m1,m2 are different, the pipe diameters are all equal but are different in length.I need to get the ...
0answers
14 views

### Magnetic field due to closed donut

How to find magnetic field due to a torroid? Thanx in advance. Im studying for jee and our prof tried to teach it but i didnt understand.help please
0answers
8 views

### components of vector regarding the direction of acceleration

The steps of how to calculate th direction of acceleration Example Calculate the direction of the acceleration when acceleration has an eastward component of 2.5m/s squared and nortward component of ...
2answers
821 views

### Finding Electric Field outside a Charged Cylinder

I'm trying to solve a problem that involves finding the electric field due to a uniformly cylinder of radius $r$, length $L$ and total charge $Q$. Well, my thought was: if I am to use Gauss' Law, I'll ...
0answers
227 views

### Can spheres leaking charge be assumed to be in equilibrium?

I am struggling with the following problem (Irodov 3.3): Two small equally charged spheres, each of mass $m$, are suspended from the same point by silk threads of length $l$. The distance between ...
1answer
19 views

### Density and Wave Speed

For a string, the formula for wave speed is $v=\sqrt{\frac{T}{\mu}}$, where $\mu=\frac{m}{L}$. The greater the linear density, the more massive the string is per unit length, the more inertia it has, ...
1answer
39 views

### Uniformly charged sheet and metal rods

A friend of mine asked me a question. Suppose there are two metal rods which are placed in front of a uniformly charged non-conducting plane one after other with their length perpendicular to the ...
0answers
18 views

### Unable to solve cable theory equation correctly

First time posting, let me know if I'm in the wrong board. I tried this over on the math board and was redirected here. In my spare time I enjoy reading outside of my field (software development). ...
2answers
92 views

### Newton's Laws ( Little Philosopical )

Suppose we are living in a universe that in that universe when you release a particle in the empty space, this particle stay forever where you release it. Which is not the case in our universe. I'm am ...
1answer
19 views

### Equipartition Theory at room temperature.

I read a statement about participation theory. The equipartition theorem is generally valid only at high temper- ature, so that the thermal energy is larger than the energy gap between ...
2answers
359 views

### Is there a way to calculate the photoelectric effect in QED via a Feynman diagram?

The photoelectric effect is the historic origin of the quantum particle description of light. From it we learn that when light is shone onto a metal single photons interact with single electrons in ...
0answers
24 views

### Directional derivative of the Ricci scalar in the direction of a Killing vector field

Do I need the Levi-Civita connection for the directional derivative in the direction of a Killing vector field of there curvature scalar to be 0? EDIT: Let $K$ be a Killing vector field and $R$ the ...
0answers
7 views

### Potential of a point charge in dielectric

My configuration is a point charge embedded in a finite dielectric geometry. I have to calculate the potential of the point charge only within the dielectric device. How should I do this?
4answers
1k views

### Why do solar cells have a window layer on top of the absorber layer and not below it?

In solar cells there is a p-n junction. P-type semiconductor (for example CdTe) is often absorber layer because of its carrier lifetime and mobilities. In case of CdS/CdTe,* CdS is n-type window layer ...
2answers
486 views

### What is the mechanism by which magnetic fields do work?

I've seen some conflicted answers to this question in texts and on the web, in the case of a dipole, for example. Do magnetic fields do work directly, or is it their induced electric fields that do ...
0answers
18 views

### Why does the weaker force deform the solid body? Elasticity problem

It's about a problem in which two forces are pushing a cylincer in different directions. Ïnside the cylinder some reactions forces appear.Here's the representation of a mass dm since it's very small. ...
1answer
243 views

### Casimir Forces and its associated Feynman Propagator

This is a continuation to my previous question, in which I began an attempt solve the Casimir Force problem using path integrals. As one of the answers there suggest I solve the Feynman propagator ...
1answer
66 views

### M-theory and Mathematics

If the framework of M-theory is the right path for a unification of gravity with quantum mechanics, is it obligatory to believe that, at a certain level, reality is not just easily describable by ...
1answer
57 views

### Lippmann-Schwinger equation and $T$ expansion

Lippmann-Schwinger equation, in operator form, is: $$T=V+V\frac{1} {E-H_0+i \hbar \varepsilon} T=:V+V\Theta_0T,$$ where $H_{tot}=H_0+{V}$ is the hamiltonian ($H_0$ is the free particle hamiltonian ...
1answer
116 views

### Would the hot windows break? [on hold]

I have a question that I was thinking about for a long time. I live in Kuwait and in the summer season the weather reach 50°C which is extremely hot specially inside a car. What if I was able to ...
0answers
12 views

### Optical fibre numerical problems [closed]

(a) What is the need for a cladding layer on the core of an optical fiber other than mechanical strength? (b) Assuming a fiber that is kept stra ight and is of length L, find the ...
0answers
36 views

### River Boat Problem with a Twist [closed]

I am trying to solve the following river boat problem. A river of width $w$ is floating such that the stream velocity varies with $y$ as $$v_R=v_0(1+(\frac{\sqrt 3 - 1}{w})y)$$ where $y$ is ...
0answers
23 views

### Need reference on the minimum moment of inertia [duplicate]

I would like to know if there is a book on classical mechanics about the following Moment Of Inertia About Centre of Mass
2answers
32 views

### Horizontal and vertical acceleration of a ball on a slope?

I understand that you resolve the components of the balls weight parallel and perpendicular to the slope in order to calculate the force due to gravity that actually acts down the slope. The ...
0answers
25 views

### What is the maximum level of heat that can be reached? [duplicate]

Heating is what everyone knows about . But does it have any limits . How much hot can anything become?
0answers
89 views

### Trebuchet launch into space

I was reading some questions on your site about using a Trebuchet to launch a payload into space. Would it be possible to use the same sort of principle, but to have, say a 100 mile steel cable ...
1answer
47 views

### What will happen if all the population all over the world jumped together at the same time in sea? [duplicate]

What can happen if a magnitude of such huge force is applied over the sea water of earth? Force applied will be average mass of each person *7 billion *9.8 .
2answers
279 views

### Was Leverrier-Adams prediction of Neptune a lucky coincidence?

According to historians both Adams and Leverrier used Bode's law to guess the distance to Neptune, which led to a vast overestimation of its orbital period (Adams - 227 years, Le Verrier - 218 years, ...
0answers
52 views

### Theoretical physics [closed]

Hi every one I am student who has a high interest in the Ising model. Please I have a question and I hope someone can help me
1answer
62 views

1answer
49 views

### Completeness relations of eigenstates in the Heisenberg picture

I've been reading Srednicki's introduction to path integrals and I'm slightly unsure of the notation that he uses for the completeness relation of position eigenstates in the Heisenberg picture. In ...
1answer
190 views

### Wormholes and the illusion of time?

I was watching a video on Youtube by Brian Greene, "the illusion of time."http://www.youtube.com/watch?v=j-u1aaltiq4 In that video, he introduces to me the idea of a "brane," or a slice of the ...
0answers
31 views

### What is special about quantum entanglement? [duplicate]

Get two pieces of paper. In secret write the same number on both papers. Transfer one paper to the Moon. Look to the paper which is left at the Earth. Voila! We know what is on the Moon paper. The ...
0answers
21 views

### what health per-captions should be taken for theoretical senerios [on hold]

so been working on some detail research and i been having some trouble since have of the experiment affects are still only theoretical but let me explain as best i can. so lately i been working with a ...

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