# All Questions

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### How are the half life of particles mathematically related to the inverse square laws?

This video https://www.youtube.com/watch?v=K6i-qE8AigE&list=PL3B0924C6A0CB8B67 explains how forces are boson particles. It talks about the other non-force particles giving off and creating bosons, ...
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### Would using a fan cause an air conditioning system to think it's cold?

Recently my office manager said this, after I requested a desk fan: ...using a fan causes a draught, which then leads the air conditioning to believe it’s cooler than it is and it then blows out ...
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### is this a good introduction to the standard model? [on hold]

I am not familiar enough with the subject matter to know if this is a good undergraduate/first course book. it is not cheap.
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### Bose-Einstein condensation as a phase transition

1.How does a non-interacting system exhibit phase transition? 2.Is partition function of BEC is non-analytic (just like in the ordinary phase transitions)? 3.What is the order of BEC phase ...
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### Why can't classical particles make Bose-Einstein condensate?

Where the quantum mechanics enters in BEC, why can't (non-interacting) classical particles condense?
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### Why does accounting for direction give the wrong result for a bouncing ball?

This a conservation of momentum problem, gathered from an old textbook. I thought it would be simple, but I seem to be goofing up somewhere in my basic conceptual understanding. PROBLEM: A 1.0 kg ...
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### Why is 0 $\nu \beta\beta$ decay often written with electron emission and not positron?

According to http://www.cobra-experiment.org/double_beta_decay/ I can see that double $\beta$+ decay is possible, but I often find neutrinoless double beta sources with the double $\beta$- decay ...
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### Johnson Noise: Source of thermal fluctuations

I've read a lot online about Johnson noise being caused by thermal fluctuations, and the Wikipedia page of thermal fluctuations attributes this to the fact that particles don't all have the same ...
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### Best way to heat something in aluminum foil? [on hold]

Let's say we have a wet piece of paper, wrapped in aluminum foil, that we need to heat up in the fastest and most energy efficient way possible (no flamethrower). What would that be? Details ...
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### How does virtual particle become real particle in Hawking radiation? [duplicate]

I am new to black hole and general relativity and am just getting introduced to these concepts. According to my understanding, virtual particle that forms because of quantum fluctuation becomes real ...
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### About the perception of the flowing of time

The user John Rennie suggested I ask the following as a new question: If time is continuous why would the perception of time being continuous or flowing be an illusion?
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### BIG source or lots of little sources [on hold]

source of any power eg audio in a speaker system for a concrete example or a car engine. you have 1000W. do I a 250W engine on each wheel or a 1000W engine under the hood and a transmission system to ...
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### Power transmission loss in a large circuit

This is a followup question to this question Consider a large circuit like the german electric power transmission network. You have a lot of of people consuming power and a lot of power stations ...
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### If you are not given a metric, which one is more fundamental: a vector or a covector? [on hold]

If we do not have the metric $g_{\mu\nu}$ for a given spacetime, are vectors $x^\mu$ more fundamental than covectors $x_\mu$ or vice versa? Why? (if the metric were given we could just raise/lower ...
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### Calculate Helmholtz Free Energy with Entropy, Work given [on hold]

it's my first time here and I hope the post complies with the general rules. My problem originates here: I'm doing a statistical physics task which unfortunately leaves me clueless atm. I keep my ...
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### Why is the Carnot engine the most efficient?

It seems that the only condition used in proving that the Carnot engine is the most efficient is that it is reversible. More specifically, the Carnot engine can be run in reverse as a refrigerator. ...
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### Confusion about Length Contraction (ex in Muon decay)

I am a bit confused about the implications of length contractions; For example, in the muon decay problem, we assume that the distance between the muon and the earth is contracted only in the frame ...
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### Ray tracing a three-way intersection

I've been studying ray tracing in media with linear velocity-depth functions. One of the key concepts I've come across is the ray parameter, and in particular the idea that the ray parameter is ...
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### Where do Newton's Laws not work? [on hold]

I'm working on high school level project about Newton's Laws and I picked topic that describes situations, where they dont work. Can you name any practical cases where they do not work? Why do they ...
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### The Higgs field and spacetime intervals

The Higgs field imparts a rest mass to certain fundamental particles, but it also seems to do something more interesting. Particles that don't couple to the Higgs field, i.e. the rest-massless, are ...
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### Kirchoff's loop law

Can any one provide me with mathematical proof of kirchoff's loop law? I am not able to understand from where to start.
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### Power transmission in a circuit

lets say you have a battery and a resistance which form a circuit. The electrons flow through the resistance. How can you visualize the flow of energy. How do you visualize the energy field. I ...
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### Why is energy of emitted particles negative?

recently I had one problem here, and in comments I got interesting thing written by user Sofia. Unfortunetly, the topic is in hold now and I can't ask her more. Here is the comment: Radio-activity ...
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### Strong CP Problem

So, as far as I know, the Strong CP Problem in QCD results from the theta angle term in the action: $i\theta\int_X F_\nabla\wedge F_\nabla$ where $\nabla$ is the gauge connection and $X$ is a manifold ...
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### How can we show that pressure is exerted sideways too?

We can show that pressure upward and downward in a fluid is caused by weight of fluid column or volume. A simple derivation of this: ...
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### Thomson problem vs. maximizing sum of distance

Given $N$ equally charged points lying on the unit sphere ("electrons"), the Thomson problem consists of finding the configuration of these points such that the electrostatic potential energy  ...
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### Gaze tracking with the pupil-glint response how does the geometry work?

I am struggling to understand the geometry behind the pupil glint response (see above) (With only one light source). I understand that you use the glint to find the corneal centre (Centre of corneal ...
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### How come milk pours smoothly from a bag?

I have seen the commercial about the new beer can where it is vented by puncturing a whole on the can (air behind water). If you just pour normally with normal cans it will get bottle necked and the ...
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### Show that there exists a Lorentz transformation such that two events are happening at the same time? [on hold]

I'm havin problems with the following exercise in a theoretical physics course: Show that there always exists a Lorentz transformation such that the two events $P$ and $P^0$ in the figure are ...
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### How to find the Kinetic energy of a quarter of a wheel? [on hold]

A wheel of mass 'm' and radius 'R' is rolling on a level road at a linear speed 'V'. What is the kinetic energy of the upper right quarter part of the wheel , considering the wheel to be of the ...