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-2
votes
0answers
6 views

Magnet rotor diameter effect on power output in an axial flux generator

I'm trying to determine which parameters of the magnet rotor have the greatest effect on power output of an axial flux generator. Obviously a very large diameter will have a greater tangential ...
0
votes
0answers
28 views

Three phase permanent magnet generator question

For my three phase permanent magnet generator, my coil plate is going to remain stationary to avoid having to use a commutator. Instead my magnetic plate will rotate. If instead of having just one ...
-1
votes
1answer
154 views

Do Physics concepts build on top of other concepts?

I am taking a calculus based physics class and I am struggling. I am wondering if I do not understand some concepts, will I be unable to understand future concepts introduced in the same class? In ...
0
votes
0answers
16 views

Log of a quantity and graphs in log-scale

Is there any difference between taking the logarithm of a quantity, and plotting a quantity in logarithmic scale?
17
votes
11answers
36k views

How do you start learning physics by yourself? [closed]

I think this question has its place here because I am sure some of you are "self-taught experts" and can guide me a little through this process. Considering that : I don't have any physics scholar ...
0
votes
4answers
418 views

Do negative numbers have any physical meaning?

So, mindlessly wandering off into space, thinking about quantum and how cool physics is, I came to a realization that... well.. negative numbers to me make 0 sense. You have either something, or not ...
73
votes
16answers
10k views

Why do most formulas in physics have integer and rational exponents?

I mean, why is $F=ma$? Why not $m^{0.123}$, $a^{1.43}$ or some random non-integers or irrational? I hope you understand that my question isn't limited just to force, energy, velocity, etc.; it also ...
1
vote
1answer
73 views

Learning Undergrad Physics [duplicate]

I am an undergrad physics student who has finished the first year curriculum: very basic mechanics and thermal physics; basic linear algebra; basic multivariable calculus and differential equations; ...
0
votes
0answers
31 views

Chemical potential and origin of pressure in a solid

Pressure of a gas is related to the rate of change of momentum of the particles; the temperature is the mean kinetic energy of the particles. Can the chemical potential be given a similar physical ...
2
votes
3answers
21k views

Uses of vectors in real life [closed]

I always wonder how vectors are used in real life.Vectors and decomposition of vectors,dot and cross products are taught in the early stage in every undergraduate physics course and in every ...
1
vote
0answers
20 views

A modern version of Landau theoretical minimum? [duplicate]

Can anyone point to me any modern books that are similar to Landau's book in scope and depth, these books used to serve as the backbone that determines one’s level of scientific culture, and since ...
-3
votes
1answer
88 views

Water level rise due to body in water

I recently came across a comment that when we push a rubber ball into water filled in a bucket, the water level rises because of the force applied by our hand (i.e. the more force we apply, the more ...
0
votes
3answers
107 views

The study of the physical universe [closed]

If physics is the study of the physical universe, wouldn't that mean chemistry, biology, neuroscience, zoology, history, economics, sociology, etc, wouldn't they all be subfields of physics? I believe ...
11
votes
7answers
1k views

Is physics rigorous in the mathematical sense?

I am a student studying Mathematics with no prior knowledge of Physics whatsoever except for very simple equations. I would like to ask, due to my experience with Mathematics: Is there a set of ...
2
votes
1answer
135 views

Question about two vehicles moving toward each other, but the answer doesn't seem correct, am I missing a key concept? [closed]

The problem statement Vehicle A and Vehicle B are moving in opposite directions on the NJTP. Vehicle A is heading south toward atlantic city while vehicle B is heading north towards Hoboken. In ...
1
vote
0answers
67 views

Is entropy a dynamical quantity [closed]

I am confused whether Entropy is a dynamical quantity or not. Gibbs entropy, and quantum mechanical Von Neumann entropy.
31
votes
4answers
13k views

Why can't energy be created or destroyed?

My physics instructor told the class, when lecturing about energy, that it can't be created or destroyed. Why is that? Is there a theory or scientific evidence that proves his statement true or ...
2
votes
3answers
221 views

Can a theory be proven by an experiment (or series of) that sustains it?

This is a question that I've always had but it wasn't until the recent news regarding the BICEP2 experiment that I really gave thought about it (please note that the question is general and not ...
0
votes
1answer
214 views

Why isn't steam/cloud blue like liquid and solid water?

Most of us here are aware as I think that pure water has a natural quest to absorb visible red colour wavelength slightly due do which liquid water and sometimes even ice appears to have a blue colour ...
0
votes
2answers
1k views

Difference between pressure and stress tensor

What is the difference between hydrostatic pressure and stress tensor?
4
votes
2answers
97 views

Does physics have some division schema which divide physical amounts into these two classes?

Does physics have some division schema which divide amounts into these two classes? : A) amounts which can be counted by natural numbers (for example many units can be counted by number of ...
7
votes
6answers
7k views

Can a scientific theory ever be absolutely proven?

I personally cringe when people talk about scientific theories in the same way we talk about everyday theories. I was under the impression a scientific theory is similar to a mathematical proof; ...
1
vote
0answers
342 views

Physics for Civil Engineering (Earthquakes, Materials Science for structures) or Fluid Mechanics? [closed]

I am currently a first year Ph.D. student in Applied Math. As an undergrad, I did not have the opportunity to take a calculus based physics course and the one I took was a general physics course where ...
1
vote
5answers
322 views

Age of universe estimates

I was recently involved in a discussion on a sister site regarding how tightly coupled Physics is with the age of the Universe (and Earth). I believe that the Earth and the Universe are both billions ...
8
votes
3answers
3k views

Please recommend a good book about physics for young child (elementary school aged) [closed]

I'm looking for a book that would be appropriate for an advanced elementary school aged kids (say, 6-11 YO) describing the basics of physics (or sciences in general) in entertaining way. The ...
-11
votes
1answer
261 views

General Physics II Practice Question [closed]

I have a test in a few hours, and my professor gave us a practice test, and I'm stuck. Could you give me a hint as to how to approach this problem, equations I could use. It's an algebra based class ...
2
votes
2answers
744 views

The meaning of 'postulate' in physics? [duplicate]

What does postulate mean in physics? What is its role in physical theories? Is it possible to break physical postulates?
7
votes
2answers
14k views

Why do car keys have longer range when held next to your head?

I first saw this on Top Gear, and assumed it was a load of rubbish, but today I tried it out and it actually works, if you walk away from the car continuously unlocking/locking it until it stops, and ...
-3
votes
1answer
306 views

Is There a List of Physics Formulas? [closed]

I am looking for a list of simple physics formulas - like $F=ma$. Is there any website/book that is a list of such equations?
15
votes
3answers
807 views

Accidental, unplanned breakthroughs in physics [closed]

There is possibly some idioms or saying like this, ``If you try too hard for something, you will never get it. If you do not aim for something, it may fall on you accidentally, not as you originally ...
2
votes
1answer
152 views

Does physics address the topic of consciousness?

Does physics address the topic of consciousness? For instance, does physics say anything about how it might arise or what might be its qualitative properties? I'm wondering because it's interesting ...
4
votes
7answers
997 views

What are the frameworks of physics?

Are there physical theories in use, which don't fit into the frameworks of either Thermodynamics, Classical Mechanics (including General Relativity and the notion of classical fields) or Quantum ...
2
votes
5answers
595 views

Why mathematical equations can describe this world? [closed]

Since I want to understand the world, I learn physics from textbooks. But I feel there is a gap between the textbook and the world. I do not know why the equations in the textbook can control the ...
0
votes
2answers
436 views

General physics landau [duplicate]

I've found Landau 's book for a first course in physics (not theoretical physics, its title is general physics),the book is freely and legally avaible on archive.org ,but it's from 1967,is that ...
0
votes
0answers
77 views

What kind of physics topics exist? [duplicate]

The question says everything I want to know, but for more details: I enjoy studying physics but the problem is that I can't find any information with a summary of all physics topics, collected ...
2
votes
3answers
544 views

What does physics study? [closed]

Wikipedia definition: Physics (from Ancient Greek: φύσις physis "nature") is a natural science that involves the study of matter[1] and its motion through spacetime, along with related concepts such ...
3
votes
1answer
821 views

Do quantum computers manufactured by D-Wave Systems, Inc. work? [duplicate]

D-wave claims to have built 128 qbit quantum computers which are commercially available? What I don't understand is that have they really been able to do this given that the scientific community is ...
1
vote
1answer
200 views

recommendation for a physics history/non-fiction book [closed]

I know that there are a lot theses being published on lives of physicists. Is there a history/non-fiction book that tracks the development of a problem chronologically? Like pieces of a puzzle. I ...
1
vote
1answer
912 views

Power radiated by the sun at different locations

I am wondering can someone help to solve second part which extends first part; The power radiated by the sun is ${3.9*10^{26}}_{watt}$. The earth orbits the sun in a nearly circular orbit of radius ...
0
votes
2answers
910 views

How to teach myself physics needed at undergraduate electrical engineer level? [closed]

I want to learn electrical engineering on my own, specifically because I'm interested in loudspeaker design, more specifically how to design active dipole loudspeakers using DSP crossovers. I have ...
1
vote
0answers
374 views

What are the biggest unanswered questions in physics today? [closed]

Are there fundamental big questions in physics that most scientists encounter no matter what they're working on, or are most questions details of smaller subtopics? What are the great unknowns of our ...
7
votes
2answers
1k views

Hydrostatic friction: why do water droplets stay at rest on an inclined glass surface?

Tjis is a non-expert question on a (seemingly simple) text-book topic. The question is about "hydrostatic friction", defined as follows. Consider a drop of water resting on a flat surface. If the ...
3
votes
1answer
10k views

Is there any significance to 1.21 GW?

In connection with a related question on Science Fiction & Fantasy Stack Exchange page: does this number 1.21 GW make any sense? What is 1.21 GWatts? With what can you compare it? Can the ...
3
votes
1answer
2k views

Why does the monitor make a cracking noise?

After switching off the monitor, there's a single crack after a while. I wonder where exactly it comes from. I know that this is normal and not an indicator of being defect. This sound is also not ...
1
vote
0answers
126 views

Scales and Hooke's Law

Bob weighs $B$ kg and when he steps on a scale, the spring inside gets compressed by $c$ meters. Assuming the scale obeys Hooke's Law, if Alice weights $A$ kg, how much work is done compressing the ...
1
vote
1answer
102 views

Retarded field interaction

I was doing the following thought experiment: imagine a particle that moves at a certain velocity. Imagine also that the particle generates a field that propagates at velocity $v_f$. Well, if the ...
-1
votes
1answer
629 views

Percentage of water that is void or empty space?

At the atomic level, at sea level on earth, what percentage of normal pure drinking water is void or empty space? What percentage of lead (the kind used to insulate from nuclear radiation) is void or ...
2
votes
2answers
186 views

What's the meaning of dimensionality?

I got amazed with this answer and as you can see, I had a little talk with joriki. He suggested me some examples such as the 2DEG. I'm stuck with some aspects on dimensionality, see this line: A ...
0
votes
1answer
167 views

is there any difference between these Differential $dx^2$ and $(dx)^2$? [closed]

is there any difference between these Differential $dx^2$ and $(dx)^2$!? what is relation between them?
4
votes
1answer
460 views

interpretation of Green function

Is there a physical interpretation of the existence of poles for a Green function? In particular how can we interpret the fact that a pole is purely real or purely imaginary? It's a general question ...