Principle Definition and 1000 Threads

Let a photon of a definite wavelength (hence a definite momentum ) start it's journey at time 0. After 8.3 minutes it hits a detector on earth. So it's position is exactly known (in fact it can be predicted for any time less than 8.3 minutes). So we have particle with definitely known momentum...

Hello! (Wave) I have a question about the proof of the maximum principle for subharmonic functions. The maximum principle is the following: The subharmonic in $\Omega$ function $v$ does not achieve its maximum at the inner points of $\Omega$ if it is not constant. Proof: We suppose that at...

For an unstable particle is it reasonable to take the uncertainty in energy as the energy it was created with? If so, why?

Homework Statement Standing in the middle of a 20 m long pier, you notice that at any given instant there are 15 wave crests between the two ends of the pier. Estimate the minimum uncertainty in the wavelength that could be computed from this information. Homework Equations [/B] Uncertainty...

Homework Statement I don't understand about some words of this problem. Does "over time" mean? Why constructive interference (CI) appear? Homework Equations I think we use The Huygens–Fresnel principle The Attempt at a Solution I choose answer 3-c But I don't know the physical phenomenon.

I'm currently designing an experiment on Double slits for a high school science fair, but I'm not sure whether it's plausible or not. I'll be spending some of my savings for this, that's why I would like to hear some feedback from more-knowledgeable people first. In this experiment, I am trying...

I can't find a derivation of d'Alembert principle. Wikipédia says there is no general proof of it. Same with stackexchange. I find it surprising so I thought I'd come here to check with you guys. D'Alembert principle has indeed no proof ?

Homework Statement Homework Equations N/A The Attempt at a Solution [/B] Okay, it is not an assignment question. I am just looking for an explanation regarding something I read. Why is the diagonal distance travel time(^-1) equal to (n_2 - n_1){(\frac{1}{c_1} + \frac{1}{c_2})} ?

Homework Statement is it a must that that the levelling work must commence and ends at benchmark or temporary benchmark of known point ? Homework EquationsThe Attempt at a Solution I think not , because we can commence the levelling work at a point of known elevation ( benchmark / temporary...

Hello everyone, I have two little clarifications to make about Huygen's principle: - Why doesn't the wave go backward? I mean, if every point on the plane acts as the source of a secondary wavelet, then, along with the envelop which makes the wave travel apparently forward, another should...

Theorem: Let ##A_1, A_2, ..., A_k## be finite, disjunct sets. Then ##|A_1 \cup A_2 \cup \dots \cup A_k| = |A_1| + |A_2| + \dots + |A_k|## I will give the proof my book provides, I don't understand several parts of it. Proof: We have bijections ##f_i: [n_i] \rightarrow A_i## for ##i \in [k]##...

So I was reading that the equivalence principle of Newton doesn't work because of a thought experiment. They said that an experimenter shoots bullets( 1 per second) from the bottom of the elevator to the top. This happens in outerspace where the elevator moves up with accleration g. And this...

Landau's nonrelativistic quantum mechanics has a "derivation" of Schroedinger's equation using what he calls "the variational principle". Apparently such a principle implies that: $$\delta \int \psi^{\ast} (\hat{H} - E) \psi dq = 0$$ From here I can see that varying ##\psi## and...

Hi All, When explaining Pascal´s Principle I had some bad time related to its application in compressible fluids. Correlation functions (forces in two points separated in space at the same time) came to my mind but at the end the doubt persists. Is Pascal´s Principle valid for compressible...

I am trying to reconcile what I understand about Pascals Law in Fluid Statics and Centripetal Force in Fluid Dynamics In fluid statics pressure always acts normal to the wall . The explanation I have seen https://www.physicsforums.com/threads/fluid-mechanics-and-perpendicular-force.733437/ Is...

Fermat’s principle states that light follows the path of least time. In textbooks, a specific formulation of Fermat’s principle is about the optical path between two points, A and B: How can a ray of light, emitted from point A, reach point B? Suppose that there is a plane wave in free space...

Are quantum superposition, Heisenberg uncertainty principle, wave/particle duality the same thing? Do they imply each other? They all seem the same to me like the wave-like nature of photons -> superposition, and superposition means there's not definite position -> uncertainty principle. Sorry...

http://www.mekanizmalar.com/how-steam-injectors-work.html In the link above, the basics of steam injector is given. Steam Injector's don't have any moving parts and doesn't consume any energy by themselves. Still, it can be able to pressurise water and inject that to a high pressure Boiler by...

I know the equation which explains how it works, but why is it like that? The closest thing I can think as to why is because of the wave-particle duality of matter given by λ=h/mv, which also explains itself. But I don't know exactly why.

See attached file. I believe my professor is incorrect. Work in must equal work out. We can imagine the work done by the mass as being a separate issue. Then, we recognize that the work done by the spring must be the same. Am I right? If not, why?

Physicists often speak of the uncertainty principle in terms of position and velocity (in momentum). But momentum is Mass X Velocity. Why is it that we can say something like "a particle with a well defined position has high uncertainty in velocity". But I never hear a statement like "a particle...

I was just a bit confused about Archimedes principle. Say an object is partially immersed in water. The weight of water water displaced will be equal to weight of the entire object or just the part immersed in water?

Homework Statement A man of mass 100 kg can pull on a rope with a maximum force equal to two fifths of his own weight. [Take g = 10 ms^2] In a competition, he must pull a block of mass 1600 kg across a smooth horizontal floor, the block being initially at rest. He is able to apply his maximum...

Hi everybody, I was reading about the Uncertainty principle and I came across the statement: "the position-space wavefunction of a minimum-uncertainty state is a Gaussian. Indeed, because it’s a minimum-uncertainty state, its momentum-space wavefunction is also a Gaussian."...

The event horizon of a black hole appears to be plastered with 'afterimages' of everything that ever fell into it. (Because gravitational time dilation makes every such object appear to stop at the event horizon.) Now, suppose an event horizon is 'full' as defined by the Pauli exclusion...

A spin-off from another thread. I consulted a couple of my GR textbooks on Huygens' principle, and found little. Wiki had a little information, which said that it could be regarded as a consequence of the homogeneity of space-time, and "In 1900, Jacques Hadamard observed that Huygens'...

I am confused about Einstein's thinking. I understand when he formulated his general theory of relativity, he wanted to incorporate 3 foundations for his theory: The relativity principle, the equivalence principle, and Mach's Principle. He believed that inertia and weight were essentially the...

Dear all, I was wondering what exactly the correspondence/relation is between Hamilton's principle (extremizing the action gives the allowed configurations) and the fact that a system wants to configurate such as to minimize its potential energy. Is there any? Somehow I can't find a decent...

Hi everyone, Apologies if this is common knowledge or a silly question, I'm just coming back to physics and I've been looking through the double slit experiments ( both double slit and delayed choice quantum eraser ) and it got me thinking about the uncertainty principle. With a photon of...

Homework Statement I am given a water tank, a small plastic cup, and some gravel. How could I use Archimede's principle to determine how much gravel to put in the plastic cup such that it sinks to a certain point (namely the rim), but then floats, so that no water is let inside the cup...

To check my understanding, imagine this scenario: You have a very small surface rigged as a light detector (the contact surface is let's say a single atom). You then fire off single photons towards it. As soon as you get a read on the detector, you know very precisely where the light is/was, and...

Hi all, I am 18 years old, and am looking to go into engineering, but I have a strong interest in theoretical physics. As such I have recently written a short research paper into the Heisenberg Uncertainty Principle, and I wondered if anyone would be willing to have a quick read and give me any...

Hey all, I was trying to compare the similarity between time dilation due to gravity and the scenario of an accelerating rocket through the equivalence principle and there's something tha blocks my understanding about their similarity. I found a good distance-time graph of the accelerating...

Hi. Is the principle of least (better: stationary) action only an axiom in classical mechanics, or can it be derived from a more profound (classical) principle? As far as I know, it can be derived from the path integral formulation of QM. Is this a more profound justification for the principle...

How come when I spin around, the universe doesn't fly apart as if its rotating around me? Why is my frame of reference that I am at rest and its the universe spinning around me not valid?

while I was studying "fermat's principle of least time" I was (and still I am) ntrigued by the fact that "out of all possible paths that it might take to get from one point to another, light takes the path which requires the shortest time". this question may be a bit philosophical but: "how"...

It is in the IB textbook. Said as an application of the uncertainty principle, consider an electron, which is known to be confined in a region of size L. We know the uncertainty in position of the electron must satisfy Δx<L. Therefore, according to the uncertainty principle, we can work out...

Hello, I was reading about Archimedes' Principle on the wiki ( https://en.wikipedia.org/wiki/Archimedes%27_principle ) and a question popped up regarding the upthrusting force (also called buoyant force) that the liquid exerts on an object that is in the liquid. I understand that the...

Heisenberg's uncertainty principle: due to experimental limitations or dual nature of matter? Or both?

Homework Statement Okay, in Carrol's Intro to Spacetime and Geometry, Chapter 4, Eq. 4.63 to 4.65 require a derivation of a difference between Christoffel Symbol. I did the calculation and found my answer to be somewhat correct in form, but the indices doesn't match up Homework Equations So...

I've been pre-occupied with Heisenberg's uncertainty principle for around four years now, and I've come to fabricate a lot of questions. The most pressing one, however, is as follows: To me, the uncertainty principle seems to reference our (relatively) poorly controlled methods to measure a...

There are lots of basic explanations on the Internet of the two most famous uncertainty principles, that of momentum-position and Energy-time, but I do not find any basic explanation of the action-angle uncertainty principle. I do not even know what angle (or what operator) is being referred to...

In fermats principle what if there is more than one path for which the variation in optical path length is stationary.Then which path would light take to reach from one point to another.

Homework Statement How many 3 digit numbers can be formed from 0 to 3 without repition Homework EquationsThe Attempt at a Solution What I did first is H = number of choices for the hundreds place T = number of choices for the tens place U = number of choices for the units digit H = 3...

How many 3 digit even numbers can be formed from 0, 1, 2, 3, 4, 5 and 6 with no repetition? My attempt: $\frac{5}{H} \times \frac{6}{T} \frac{0}{U} = $ 30 numbers ending with zero not including two digit numbers starting with zero$\frac{4}{H} \times \frac{6}{T} \frac{2}{U} = $ 24 numbers...

Consider an ensemble of identically prepared pencils balanced on its tip. If a pencil is precisely vertical, ##x=0##, and precisely at rest, ##p=0##, then it will never fall. But some pencils in the ensemble would fall, because according to the uncertainty principle, the standard deviation...

From the following definition, it seems that the uncertainty principle is an epistemological statement. "Heisenberg's uncertainty principle, is any of a variety of mathematical inequalities[1] asserting a fundamental limit to the precision with which certain pairs of physical properties of a...

Hello, It's been puzzling for me to try to understand this issue. To begin with it is clear that there are basically two principles, the Position-Momentum uncertainty and the Time-Energy uncertainty. It is also clear that there are at least two different interpretations attached to both. One is...

The principle of the least action, that the particle will take the path of least Lagrangian, here given as T-U, is Hamilton's principle in classical mechanics. I am wondering if this is just an empirical, experimental observation that is not mathematically driven from elsewhere, just like...

am reading Sean Carroll's pop-science book 'From Eternity to Here' and am having trouble connecting the links in his discussion of the Holographic Principle. At the outset, I would ask that you try to answer in terms of Carroll's discussion and without moving into concepts much more advanced...