Principle Definition and 1000 Threads

Einstein's equivalence principle states that: The sets of inertial frames in the real world that correspond to (portions of) the ideal set of inertial frames discussed in special relativity consist of freely falling local frames. In other words,can we say that since all the local frames are in...

The uncertainty principle says that you can't know position and velocity of particle at the same time. So particular we can not say that the particle is at rest at some point because then we would know it is not moving and we would know exactly where it is. So my question is if we send the...

Instead of just taking one measurement of the particle, you take a 2nd measurement in addition thereby gathering more information about the particle then the uncertainty principle allows?It would be possible to extend out to an arbitrary number of follow-on measurements thereby measuring...

Hi everybody, my question is a curiosity on the (generalized) Heisenberg principle: ## \sigma_{x}\sigma_{p} \geq \frac{\hbar}{2},## where ##x,p## are the usual quantum operators and ##\hbar## the Planck constant divided by ##2\pi##. If I understood correctly, Gaussian states that are solution...

That's confusing. If the velocity at the exit is increased, that simply means kinetic energy is increased. But as the pressure is decreased and suppose the process is adiabatic (in case of compressible fluid), that means the temperature too is decreased. That simply means the enthalpy of the...

Bernoulli's principle states that under dynamic conditions total energy inside the fluid container remains constant. and if area is decreases then pressure decrease . and Pascal states that pressure = force/area . here if area decreases then pressure increase . I'm getting confusing...

Is time taken by light always minimum between two points. If yes then what is wrong with Fermat's original statement?

I have found that some people say “yes, definitely”, and other days “no, definitely not”. Those who say “no” seem to regard PLA as merely a neat way of packaging the equations. Those who say “yes” seem to regard PLA as somehow fundamental. (There have actually been two recent books on this...

Homework Statement I was reading through the principle of a capacitor and I am unable to understand one of the statements. My textbook says the following- Consider an insulated metal plate A. Let it be connected to a voltage source and charged to a maximum. Now an uncharged plate B is brought...

I am reading Micheal Searcoid's book: Elements of Abstract Nalysis ( Springer Undergraduate Mathematics Series) ... I am currently focussed on Searcoid's treatment of ZFC in Chapter 1: Sets ... I am trying to attain a full understanding of Searcoid's proof of the Pairing Principle ... The...

I have seen that the more a particle has a high energy, i.e ##E##, the more its lifetime is short, respecting so the uncertainty principle. But by the definition of this uncertainty principle : ##E\,\Delta t \geq \dfrac{\hbar}{2}##, I can write : ##\Delta t \geq \dfrac{\hbar}{2E}##, then...

Consider 2 lifts ,one on ground and other on acceleration, principle of equivalance says you can't find you are on a gravitational field, or accelerating. g decrease when r increase so I can find which lift on gravitational field ?

What was the problem between Maxwell's EM theory and the principle of relativity? Why went the theory against the principle? I understand that the EM theory says that Light was a wave and ether is it's medium. On the other hand the principle of relativity says that there is no state of...

Is there a controversy over the EP? What I mean is: is it considered to be false beyond any doubts or on the contrary it is absolutely true and doubts about its validity are only misinterpretations? I know that the question it's not so simple because there are many EPs, strong, weak, etc. but I...

Consider the pairing term in Weizsäcker formula. Here https://en.wikipedia.org/wiki/Semi-empirical_mass_formula#Pairing_term it is claimed that: I don't understand how Pauli exclusion principle should be the cause of this. This term comes from spin-spin interaction (or "coupling"), but I do not...

If the uncertainty in the age of the Universe is ##\Delta t## then the Uncertainty Principle implies that it has an uncertainty in its energy ##\Delta E## given by $$\Delta E \ \Delta t \sim h.\tag{1}$$ If this energy fluctuation excites the zero-point electromagnetic field of the vacuum then a...

Hi, If I understand correctly, closed time like curves (CTC) are world lines that close upon themselves. What would an observer measure to demonstrate a CTC?

Homework Statement Construct suitable circuit and record your finding to illustarte the operational principle of the sensors: sound, light Results: Distance from light source (cm) - light intensity (lx) 0 - 1000 10 - 400 20 - 260 30 - 200 40 - 190 50- 180 experiment involved moving a...

What assumptions underlie the classical uncertainty principle? The principle doesn't seem to apply when I want to know the precise pitch of a tone from a bowed violin string, since I can measure the duration (as precisely as I want) of the beats produced when I interfere it with a sine wave of...

I'm having trouble trying to remember this: suppose I have an operator ##A## and an eigenfunction ##\psi = c_1 \psi_1 + c_2 \psi_2## for ##A## so that $$ A\psi = a\psi$$ The expected value is ##\langle A \rangle = \langle \psi|A|\psi \rangle = a## After a measurement ##a## can be ##a_1##...

Homework Statement Show Hausdorff's Maximality Principle is true by the Well-Ordering Principle. 2. Relevant propositions/axioms The Attempt at a Solution Case 1: ##\forall x,y\in X## neither ##x\prec y## or ##y\prec x## is true. Hence any singleton subset of ##X## is a maximal linear order...

I'm watching a freshman-level lecture trying to take students through the energy-time uncertainty principle. (They've covered the position-momentum uncertainty principle). In the lecture, the professor starts by saying that we have a particle with some momentum, but that we can't know the...

I am struggling to understand the induction proof of the pigeonhole principle in my textbook. The theorem and the proof, from Biggs Discrete Mathematics, is pasted below, and I will explain further (see bold text) what I am having trouble with. Theorem. Let m be a natural number. Then the...

Hello! I am a bit confused about the Pauli exclusion principle. Let's say I have 3 electrons. Due to energy considerations the first 2 go to the ground state, and they can be only 2 electrons there, because the position wavefunction has only one option ##\psi_{100}## (and again due to energy...

I'm working through Gregory's Classical Mechanics and came across his derivation of energy conservation for a system of N particles that is unconstrained. We get to assume all the external forces are conservative, so we can write them as the gradient of a potential energy. There's a step he...

Homework Statement [/B] Estimate the lifetime of the excited state of an atom whose natural emission line width is 3.00 × 10−4 eV. Homework Equations $$ \Delta E \Delta t = \frac{1}{2} \times \frac{h}{2\pi} $$ $$ \Delta E \Delta t = \frac{h}{2\pi} $$The Attempt at a Solution I think all I...

Has anyone conjectured that the redshift associated with Hubble's constant can be explained by Heisenberg's uncertainty principle? Another words, the further in space away from us a photon is emitted from a galaxy, the longer in time it takes for the photon to reach us. Since the photon has a...

Hello, When we applying the principle of least action, we require ##\delta S=0##, which corresponding to the action S being an extremum. I am just wondering why do we say that the action is a minimum instead of a maximum for a physical path? Can I use the path integral to explain this problem...

[Moderator's note: Spun off from another thread due to topic change.] Can I say that "being at rest in a uniform gravitational field is locally equivalent to accelerating in flat spacetime, free falling in a uniform gravitational field is locally equivalent to nonacceleration in flat spacetime ?"

Do cyclotrons make use of the principle that the cyclotron frequency is independent of energy?

I was reading an article about holographic principle and M-cosmology and how could they be used to interpret QM mechanics. But there's a part where it talks about holographic principle in a strange way to me. What does this article mean with this?: "Since for the participant observer the...

Hello, I am developping a Python (/Pyomo) package for simulation and optimization of some industrial processes. I want to create global (simplified) models for heat exhangers (and more) and avoid differential equations. (to decrease the number of variables of the problem) Most often the...

Homework Statement Homework EquationsThe Attempt at a Solution I only need help on part c. I tried to add up t1 and t2 and differentiate it. However what variables should I differentiate with respect to? If I differentiate with respect to f I got f=root(2) * h, if i differentiate with respect...

There is a city with 100,000 people, which has 3 newspapers: A, B and C. 10% read A, 30% read B, 5% read C. 8% read A and B, 2% read A and C, 4% read B and C and only 1% read all of them. a) How much people read only one newspaper? b) How much people read at least two newspapers? c) If A and C...

Some time ago there was a similar thread https://www.physicsforums.com/threads/clock-hypothesis-gravity-time-dilation-and-equivalence-principle.929838/ but what I want to discuss is similar but not the same and I would like to specify my question in such way, that it hopefully won't go sideways...

Hi, so I have a problem that I am working on and I think that I understand Archimedes principle but the density that I am calculating is just absurd. The problem is as follows: "A geologist finds that a moon rock whose mass is 9.28 kg has an apparent mass of 6.18 kg when submerged in water...

Hi, I am trying to solve a control problem where I have to minimize the fuel consumption of a vehicle: $$J=\int_{0}^{T} L(x(t), u(t),t) + g(x(T),T)dt$$ ##L(u(t),v(t))=\sum\limits_{i,j=0}^{2} K_{i,j} u(t)^i v(t)^j ## is convex (quadratic) and the term ##g(x(T),T)## is to have a constraint in the...

Is it somehow possible to know both noncommutating properities of eg. a partcle, with using two indicators? Eg. two teams, with one is studing the momentum, and other one the position - then it's somehow impossible to exchange informations?

A very simple question: if given a vector ##v(t_0)## and two group functions ##G(t)## and ##G'(t)##, here ##t## is the parameter of time, the two group functions act on ##v(t_0)## simultaneously, then we can get a vector field ##v(t)##, then how to get ##v(t)##?

Can whatever type of information be encoded in a boundary in holographic principle? in a question some years ago regarding holography (https://physics.stackexchange.com/questions/75436/are-stokes-theorem-and-gausss-theorem-examples-of-the-holographic-principle) It is said that AdS/CFT is the...

Homework Statement I am given 2NH3(g) + 2.5O2(g) ⇌ 2NO(g) + 3H2O(g)+heat. By using Le Chatelier's principle, describe and explain four ways in which an industrial chemist could increase the yield of nitrous oxide. Homework EquationsThe Attempt at a Solution For 2NH3(g) + 2.5O2(g) ⇌ 2NO(g)...

Does Hyugens principle apply in three dimensions ? If a surface wave (for simplicity an ocean wave) is propagating along the x-axis we know that this wave ray is a point source for wavelets on the y-axis but what about the z axis? If this diagram was 3d would we see a spherical wave front...

Homework Statement A large water tank, open at the top, has a small hole in the bottom. When the water level is ## 30## ##m## above the bottom of the tank, the speed of the water leaking from the hole: A. is ##2.5## ##m/s## B. is ##24## ##m/s## C. is ##44## ##m/s## D. cannot be calculated...

Homework Statement Which of the following statements about Pascal’s principle is true? A. It is valid only for incompressible fluids B. It explains why light objects float C. It explains why the pressure is greater at the bottom of a lake than at the surface D. It is valid only for objects that...

My understanding of Bernoulli's Principle is something like this: Pressure is inversely proportional to velocity. Fluid flowing through smaller cross-sectional area has increase velocity & decrease in pressure. Also P = F/A... so would force also decrease for fluid going through small area...

Another thread (now closed), got me thinking about the holographic principle. So I looked it up and found a couple of surprises. First it seems to be attached in some peculiar way to string theory. Second, it seems to be applied more restrictively than it I thought. It's especially that...

Equivalence principles explains why lite bend towards massive objects, Einstein uses a moving lift to illustrate this, the light will seem to be bending if the lift is moving, but for a stationary lift, it will not because the position it strikes is stationary. So I think it is not correct...

Homework Statement Verify Superposition Principle using Matlab, given a DC source of 100V, an AC source of 50V, 60Hz and three resistances, R1=10 ohms, R2=20 ohms and R3=15 ohms. I created the circuit below and ran the program. Result: Homework Equations None, just running the program...

Hello Forum, Going through Griffith's book last night, I read a good paragraph on page 111 about the canonical uncertainty principle for position and momentum in the x direction: $$\sigma_{x} \sigma_{p} \geq \frac{\hbar}{2}$$ If we could make 100,000 identical copies of a system in exactly...

If we have a particle, say, an electron and we shoot it straight through an empty box. This box is surrounded by light sources on its two sides: So, if you consider the above cube, if we shoot a particle in a straight line such that it crosses the face ABEF and it crosses the face HGDC through...