# All Questions

3k views

### Where is the candle hottest?

Where is the hottest spot above a lit candle? In the flame or just above the flame tip or some cm above the flame or other? Update My question more precisely concerns the heat energy I can get from ...
65 views

### Searching for a collaborator for a physics simulation of multi-party elections [closed]

I have completed a series of physics simulations on Matlab to find the equilibrium positions of parties in 2-D or 3-D voting space and compared them to the optimal positions that would provide the ...
853 views

### Calculating the electric relative permittivity of fluid or medium?

I'm unsure of how to calculate the permittivity of a fluid. Permittivity differs from one fluid to another: $$\varepsilon=\varepsilon_r\varepsilon_0$$ Since it is an electrical property combined ...
409 views

### Why relative positions of stars and other objects in a galaxy do not change over the year

Though the identifiable stars in a constellation(say andromeda) and galaxy(say andromeda galaxy) are situated light years apart, why isn't the galaxy appearing at different positions(with respect to ...
544 views

### Newton's third law and General relativity

Is Newton's third law valid at the General Relativity? Newton's second law, the force exerted by body 2 on body 1 is: $$F_{12}$$ The force exerted by body 1 on body 2 is: $$F_{21}$$ According to ...
491 views

### Dynamical supersymmetry breaking and Witten index

Witten index, defined as ${\rm Tr}(-1)^F$, determines if supersymmetry is spontaneously broken or not for a given model. However, it is also known that supersymmetry can be dynamically broken. One ...
328 views

### Quantization of Nambu–Goto action in multiples of Planck's constant?

Isn't it possible? Quantization of Nambu–Goto action $$\mathcal{S} ~=~ -\frac{1}{2\pi\alpha'} \int \mathrm{d}^2 \Sigma \sqrt{{\dot{X}} ^2 - {X'}^2}~=~nh\qquad n \in\mathbb{Z}.$$
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### Estimation nuclear force between proton and neutron in deuteron

Is there an estimation of nuclear force between proton and neutron in deuteron to say What is the strong nuclear force between them? 1N? 10N? 100N? 1000N?
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### Can we transfer the charge on a plate of a capacitor elsewhere?

I know it is hard , but can we transfer the charge on a capacitor plate elsewhere?
2k views

### Why can't “missing mass” (=dark matter) be photons?

After a star lives and dies, I assume virtually all of its mass would be photons. If enough stars have already lived and died, couldn’t there be enough photon energy out there to account for all ...
602 views

### Air density equation in stratosphere

Does the density equation for air on Earth change in the outer atmospheres? I am generating a model for the Red Bull Stratos jump and am trying calculate a precise air density function.
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### How does Boscovich's argument show that force must act at a distance?

Apparently Boscovich's argument shows that force must act at a distance: But how did the velocity of the faster body come to be reduced from 12 to 9, and that of the slower body increased from 6 ...
122 views

### How to find exponential values

I have a power equation for flow between two circular disks on a common axis as stator and rotor, which follows, $$P = \frac{n^a}{G}\tag{1}$$ Where: $P$ = power, $n$ = revolution (1200 rev/min), ...
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### If acceleration causes relative time dilation does the eventual deceleration reverse it?

If acceleration causes relative time dilation does the eventual deceleration reverse it? For example: traveling to Alpha Centauri Based on me reading this site: ...
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### What causes a ring-like image around light of the moon?

I just encountered an interesting image in sky. As you can see in following images there was a ring-like image around light of the moon. I don't know if it was clouds but it was looking like it is far ...
1k views

### Can any rank tensor be decomposed into symmetric and anti-symmetric parts?

I know that rank 2 tensors can be decomposed as such. But I would like to know if this is possible for any rank tensors?
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### Is there a default notation for 4-vectors while handwriting?

In printed paper 3-vectors can be denoted bold italic while 4-vectors can be denote just bold. While handwriting 3-vectors are denoted by arrows above letters. Is there a similar way to denote ...
197 views

### What maintains quark spin alignments in baryons?

What maintains quark spin alignments in baryons? The $uud$ proton and $udd$ neutron are both spin 1/2, implying that two of their spin 1/2 quarks are always parallel and the other is always opposed. ...
265 views

### What time scale is used by the JPL HORIZONS system?

I'm confused by the ust of the term "UT" in the description of time scales used by the JPL HORIZONS system. Their manual states that UT is Universal Time This can mean one of two non-uniform ...
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I have a $0.40 Kg$ of mass that has $v= 0.5 m/s$, and then crashes with a spring with constant $k = 750N/m$ Whats the distance that the spring was compressed? I was using the equation $W_{r} = ... 2answers 519 views ### deriving a Lorentz transfomation for velocity vector components If$S'$and$S$are two different inertial reference frames and$S$moves along the$x$axis of$S$in a standard configuration, then the Lorentz transformation will be: $$x'=\gamma(v)[x-\beta ct]$$ ... 3answers 7k views ### How air humidity affects how much time is needed for heating the air? In cold weathers it is suggested to put a humidifier since the air gets too dry. I wonder how the humidity affects how much time is needed to get the air at a temperature of 20 Celsius degrees? I mean ... 0answers 250 views ### Representing a polarization vector for light as a 'manifold of two state' Explain me these projections please Context: I was reading a paper (Phys. Rev. A 68, 052307) which involved mesoscopic coherent states of light. There, in order to calculate the uncertainty of a ... 1answer 2k views ### How to calculate the supporting force for a cantilever beam? [closed] How do I find the supporting force$R_A$and the moment$M_A$? Should I use the sum of moments or? 2answers 441 views ### What was the muzzle velocity of a home made gun launch strait in the air if air time was 8.2sec? I built a potato gun and wanted to calculate the muzzle velocity. I remember from physics that I could run the numbers by calculating time from launch until landing. After pointing strait into the air ... 1answer 319 views ### What is the definition of density as a function? (Before I start, I don't know which tag is suitable for this post. Please retag my post if it bothers you.) Let's say there is a string on$[0,1]$with a mass given by$m(x)$. ($m(x)$means the mass ... 3answers 10k views ### Why does an object with higher speed gain more (relativistic) mass? [duplicate] Today, in my high school physics class, we had an introductory class on electromagnetism. My teacher explained at some point that an object with a very high speed (he said it started to get somewhat ... 4answers 1k views ### Fast cool down of “things” in the kitchen Is there any fundamental physical reason (thermodynamics/entropy?) behind the fact that there doesn't exist home appliance for fast cool down of food/drinks? I know that there are some methods ... 2answers 1k views ### How can some-one independently do research in particle physics? [closed] I'm not affiliated with a physics department and I want to do independent research. I'm working my way through Peskin et. al. QFT now. Let's say that I've finished Peskin et. al. and Weinberg QFT ... 2answers 331 views ### Exploding Earth I have always heard that the Earth, due to its structure, cannot explode. Now, I'm quite fascinated by astronomy physics but I admit I only hold some more than basic knowledge. In any case, even ... 0answers 126 views ### Can we use a warp bubble for nuclear fusion? I understand NASA is now experimenting with a tweaked Alcubierre drive. Apperantly some physicists predict crazy heat (hotter than the sun) inside the warp bubble caused by Hawking radiation (recent ... 1answer 57 views ### Can objects, animate or inanimate, be constructed out of basic particles? If all the elements are made of protons, neutrons and electrons, but some elements are much rarer and more expensive than others, would it be possible to break apart atoms of one element and make ... 3answers 176 views ### Special Relativity [closed] Could someone explain to me how special relativity works? I know there are thousands of sources and databases of knowledge out there, but I find it difficult to understand, even after reading up on ... 3answers 794 views ### How do the Einstein's differential equation of the curvature of spacetime come out of Einstein's field equation? The classical theory of spacetime geometry that we call gravity consists of the Einstein equation, which relates the curvature of spacetime to the distribution of matter and energy in spacetime. ... 1answer 127 views ### Diffraction through the slit In book "Quantum Mechanics and Path Integral", 3-2 Diffraction through the slit: Under the fig. 3-3, why did Feynman say that we cannot approach the problem by a single application of the ... 0answers 71 views ### Elimination of the node Recently I have been reading a lot of astronomy papers on reductions in models of the solar system. A reoccurring concept is the elimination of the node. However, they never explain what the node is ... 1answer 499 views ###$E^2 = (mc^2)^2 + (pc)^2$: What units are used to measure$E$,$m$,$c$and$p\$?

$$E^2 = (mc^2)^2 + (pc)^2$$ If I am using this equation to figure out the energy of something, what units would I use? Would it be the metric system? I.e. kilograms ...
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### Assuming SUSY is found to be incorrect, what would then be the most compelling candidates for dark matter?

From what I've read, the only remaining candidates appear to be either sterile neutrinos or MOND (MOdified Newtonian Dynamics -- it does seem to keep changing.) Did I miss anything else plausible?
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### Recent Higgs boson observation and credibility of superstring theories

Data are coming in, and it seems that recent Higgs boson observation is eliminating many SUSY models. If so, what is happening to superstring theories, like M-theory?
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### Can I use computer fans and tubes to lower the air temperature below dew point?

I suppose to build a small dehumidifier, but I am narrowing the question down into its logics. I have relatively powerful computer fans, water cooling radiator and some metal tubings. With the idea ...
207 views

### Image Formation (Convex-Convex lenses)

I'm given with these data: Lens 1 and lens 2 are convex lenses with different focal lengths Distance of object from lens 1: 50 mm Distance between lens 1 and lens 2: 100 mm Distance of final image ...
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### How long in advance can dates of moon phases be accurately predicted?

When researching an article on Chinese New Year I found a few websites that predict the dates of Chinese New Year (CNY) tens - or sometimes even hundreds - of years in advance. I´m wondering how many ...
221 views

### Difference between Quark-Gluon Plasma and Color-Glass Condensate?

From the news. Apparently they are very similar, yet different.
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### Question on Total, Orbital and Spin Angular momentum

I am reading about the total, orbital and spin angular momentum, and I am not clear as to what these generators actually do after exponentiating. Could you give me a physical picture of what happens ...
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### How to find the distance of the source of sound in this problem? [closed]

On a cloudy day, the sound of thunder was heard 4.5 s after the flash of light was seen. How far was the cloud? Given that speed of sound = 340 m/s This is what I've tried: speed of light(c) = 10^6 ...
8k views

### is it possible to flow current in open circuit?

First , i don't know much about chemistry and physics. I'm just a graphic designer but i have this question in my mind. I'm sorry if this question is too basic and use 'generic' language. As i know ...
447 views

### How do you find the speed of sound in the problem? [closed]

A stone is dropped into a 40m deep well. The sound of the splash is heard 2.95 seconds after the stone is dropped. Find the speed of sound.
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### How was the Oh-My-God particle observed?

How exactly was the Oh-My-God particle (ultra-high energy cosmic ray) observed and its energy measured?