Principle Definition and 1000 Threads

Homework Statement A beam of 50eV electrons travel in the x direction towards a slit of width 6 micro metres which is parallel to the y direction. The diffraction pattern is observed on a screen 2 metres away. Use the Heisenberg uncertainty principle to estimate the minimum uncertainty in the...

Which of them comes first,(I mean the concept or the theory)? Did Heisenberg come up with the idea of uncertainty principle because of the discover of the wave particle duality? Thanks for paying attention~

Homework Statement A proton traveling at a speed of 3.00*10^6 m/s north through a magnetic field experiences a force of 1.50*10^-14N up. What is the magnitude and direction of the magnetic field? Include the physics principle Homework Equations Fm=qvB[/B]The Attempt at a Solution I solved for...

Whilst I understand that entropy is a measure of the number of specific ways in which a system may be arranged. The units for entropy don't make sense to me intuitively. Why joules per kelvin? What way at all does that show how "disordered" a system is. When I hear joules per kelvin, I think of...

If Classical Physics (Newton, Maxwell, Einstein) operates on the principle of determinism and causality, Quantum Mechanics operates on the principle of probability, then would the Unified Field Theory (or Theory of Everything) operate on a yet different principle? Or am I being too general?

Hi! Question: Is the following possible in principle or am I missing some important rules in relativity which makes it impossible? Imagine a spaceship which can travel at relativistic velocity. It is 10 kilometers long and equipped with two sensors, 1 and 2, placed in each end of the ship...

Theory and my Understanding: So I understand how the frank condon principle let's us effect electronic transitions instantaneously, since the motion of nuclei (on the timescale of such electronic transitions) is quite slow. Consequently, when a photon of light is absorbed you can have an...

I have been trying to fully understand this concept of Bernoulli's Principle , the Venturi effect and fluid velocity and energy. I need to grasp this to develop an idea that I have been working on. 1. As water is forced down a narrowing pipe, as the pipe gets more narrow, it means it losses...

I understand that the electron degeneracy principle states that no two electrons can occupy the same space at once. However, I do not think I clearly understand the physics behind that. I talked to my physics teacher about this and he said it had to do with the electron spin; I thought it was...

hi, please if somebody could explain why anybody would consider the "action" and is there any proof that the minimal action actually gives the correct route of a problem?

My friend and I had this argument about whether or not the uncertainty principle is applicable to stationary particles. I maintain that it is, because the principle is really about predictability ( isn't it?) But he maintains that it doesn't. So I would just like to clear things up . Does it or...

Desloge (1989) published the article: ## '##Non-equivalence of a uniformly accelerating reference frame and a frame at rest in a uniform gravitational field## '##. His result, briefly resumed: a uniform gravitational field is not flat, is quite interesting. But the way he proves the result is...

Well, I do understand what mathematical theorem means, and I also know what differential equation is but I don't really get why sometimes certain things are called "equations" instead of "law" (Maxwell's equations, nobody calls it Maxwell's laws) and conversely some equations are called laws...

How do I find the time of travel along a path say APB of tetha and show it's maximum at P= P(0) considering a ray of light traveling in a vacuum from A to B with reflection at P in the same vertical and as A and B, according to the law of reflection,the actual path goes via point P(0) at the...

Hello Is the principle of minimum action applicable to nonholonomic systems? Why? If this question is already answered in this forum, just tell me, and I will delete this thread. Thank you for your time :) Greetings PS: My mother language is not English, so I'll be glad if you correct any...

Homework Statement A bullet is shot from a rifle. 1) if the position of the centre of mass of the bullet perpendicular to its motion is known to have an accuracy of 0.01 cm, what is the corresponding uncertainty in its momentum? 2) If the accuracy of the bullet were determined only by the...

Homework Statement I've been attempting this problem all day now. My current submissions are 10.6N and I keep getting 7.04N every time I retry it but this is also wrong. Can somebody please help me out so I can figure out what I'm doing wrong? Thanks for any help in advanced! The 3.35kg collar...

First off I just want someone to check and see if I got the right answer because I have no way of telling if it is the right answer or not. I am pretty sure I have the right answer but I have no way of checking. 1. Homework Statement A spring with a stiffness ks and relaxed length L0 stands...

Hi Folks, Is it possible to calculate the principle moments of inertia acting along the principle axes of inertia given the moments of inertia and their directional vectors. Ie , I have the following information Moments of inertia ##J_1, J_2,J_3=18kgm2,15kgm2,6kgm2## and the directional...

Can one use uncertainty principle for Classical mechanic wave and still get the same equation for Quantum mechanics, as in (root-mean square uncertainty of position) (" of momentum) > hbar/2? It's just that V(x) [Potential equation] is same for both Classical and Quantum mechanics so I wonder if...

I first came across this concept in a Scientific American magazine. At the time it was nigh impossible to find much more information on it. Even now I am having a hard time wrapping my head around it. So I have a few questions. From what I understand, it basically says: Every single bit of...

I finally understand the principle of being able to imagine light as having 2 perpendicular components of electric field, to use an analogy from an earlier thread, its just as a weight on a slope may be considered to have 2 componants. Anyway, for this example nx = ny = no and nz = ne. Light is...

Homework Statement The system shown in Fig. 2-6 is in static equilibrium. Use the principle of virtual work to find the weights A and B. Neglect the weight of the strings and the friction in the pulleys. Homework Equations Conservation of gravitational potential energy. The Attempt at a...

Dear all, I would like to ask you one basic thing. I know exactly how resitor works on electrical base. But I want to know if I know good how it works on physical base. This is my knowledge from primary school (for basic circuit). Input current and output current in circuit is still equal. This...

Does the Heisenberg Uncertainity Principle mean: 1) If a particle is confined within a length x then it must jiggle around with a momentum given by p ~ h/2x PI OR 2) If we measure the position of a particle to an accuracy of x then its momentum will be uncertain by ~ h/2x PI

Hi all, I'm not 100% sure this belongs in this topic but it was a problem I was given in a quantum mechanics lecture so here goes, sorry if I am wrong.Anyway I was given a hamiltonian H= T+VWhere T is kinetic energy and av is potential, and asked to use dH/dt= 0 to find an analogy between...

Homework Statement Verify that e^x and e^-x and any linear combination c_1e^x + c_2e^{-x} are all solutions of the differential equation: y'' - y = 0 Show that the hyperbolic sine and cosine functions, sinhx and coshx are also solutions Homework Equations Principle of Superposition for...

Homework Statement Hopefully it is not a faux pas to post two questions relatively close together in time. This is more of a conceptual question than a calculation based question. An electron is confined to a region of space of the size of an atom (0.1 nm). a) What is the uncertainty in the...

Homework Statement Draw a sketch and show/explain how the induced secondary voltage and current "moves" when the primary current "breaks" the instant the switch N is opened. See the attached image below (I apologize for my awful paint job...). Homework Equations The Attempt at a Solution...

hello, I want to apply the virtual work principle to a continuous mechanical system to derive equilibrium equation, naemly, a long thin bar with one end fixed in the wall and other end applied with pressure P. but I can not derive the correct equilibrium equations. I hope some expert could give...

dear all, the virtual work pinciple can be used to derive the equilibrium equations for the mechanical systems. however, when I want to apply it to a continuous system, I found it can not give out the simple equilibrium equations. there should be something wrong with my thinking. I expect some...

Someone noted that the famous muon half-life experiment, supporting time dilation in SRT, seems to violate the equivalence principle of GRT. The very large radial acceleration in the experiment does not appear to cause any additional slowing. The acceleration does not seem to have an equivalent...

I am trying to understand the (possible) couplings between scalar chemical reaction phenomena and vectorial phenomena such as heat conduction and mass diffusion. It is argued in the literature that I have read that the usual assumption of cross coefficients for scalar+vectorial phenomena only...

One argument against Mach's principle is the speed of light restriction. How could the distant cosmic mass of the universe instantaneously have a local effect on an accelerating mass? But could we view this from the perspective of a field that is already presently locally at all points in...

Homework Statement The square of a wave function gives the probability of finding a particle at a given point. What is the probability of finding an electron in a 1s orbital within a volume of 1pm^3, centred at: a) the nucleus b) 50pm away from the nucleus? Homework Equations...

While reading Special Theory of Relativity from Feynman Lectures, I fell into the confusion about invariant speed of light. What I'm asking for is an explanation about this. No matter whether physical explanation or mathematical. So my question is Why the speed of light is same for a person...

Hi! In classical electromagnetic theory the energy of an electromagnetic wave is proportional to its amplitude squared. In contrast, the quantum mechanical equation ##E = \hbar \nu## states that the energy is proportional to the frequency of the wave (photon). Now, according to the...

I've seen it stated in many places that the reason why atoms don't collapse is due to the pauli exclusion principle. The exclusion principle is given as a required anti-symmetry in the wavefunction of electrons. I don't understand how this principle was derived, or where it comes from. (I've...

Homework Statement There are two parts to this question... a)Which of the following are correct representations of The Momentum Principle? (assuming a small-enough Δt whenever it shows up) 1) \frac{Δ\vec{p}}{Δt} = \vec{F}|| + \vec{F}⊥ 2) For every action there is an equal and opposite...

Hi. I have a question about the Holographic Principle. I've been looking up things about it for a while now, and I think I understand it. The total content of a space is propositional to the area surrounding it and not the volume. The thing I'm having trouble with is how everything seems 3d...

http://phys.org/news/2014-08-duality-principle-safe-apparent-violation.html It seems an experiment was performed back in 2012 that measured which-way information, but also found interference. (I may have come across it at the time, but cannot recall reading about it from memory.) How could this...

While deriving lagrangian equation using D'Alembert's principle, in Goldstien, they defined a variable called "virtual displacement". Why do we need a concept called virtual displacement? What is its signigicance in classical physics?

Hi pf, I have recently watched a YouTube physics video from SixtySymbols channel which is a channel of short physics videos presented by professors of physics from Nottingham University. The video (pasted below) argues that because of inertial mass and gravitational mass being equivalent this...

Hello, Does this concept of "Free energy principle ( https://en.wikipedia.org/wiki/Bayesian_approaches_to_brain_function#Free_energy )", developed by Karl J. Friston, showed its relevance ? ie is it a fruitful concept in the field of neuroscience and in biology ? Patrick

According to d'Alembert's Principle, the virtual work done by constraint forces must be zero. I have a few things needing to be clarified. First, as we know from friction, d'Alembert's Principle is not always true (friction usually does work, and is not normal to the constraint surface). On the...

I find it hard to believe that the only factor important in computing aircraft lift is Bernoulli's principle. Doesn't good old Newton's Second Law play an effect? In other words simply deflecting the airflow downwards. Does anyone know the relative importance of these factors? (EG for a...

I've been looking for this proof for months but I wasn't able to find something...

I watched a video about particle physics and there I saw something strange(for me) (link is here) and there in 13:44 I saw [x,y] I didnt understand because I think uncertanity principle exist only between position and momentum but he make uncertanity between two coordinates .Can somebody...

According to Fermat's Principle (modified version) a light ray takes an extremum path. Can anyone explain the physical reason behind this? I mean, sure the light can take the least path but how can it take the longest path? And if it can indeed take the longest path, why not the paths shorter...

Hi all, I Dont understand a principle from beardon, Algebra and Geometery chapter 2 real numbers... Please answer In the principle of Induction what is 'm'? and what is 'm+1'? are m elements of A how can m+1 also be an element of A?? if A is a subset of natural numbers how it be all...