Principle Definition and 1000 Threads

It is known that equivalence principle is good for understaning of general relativity (GR). This means comparison of the elevator and falling in homogenic gravitational field. But, I here somewhere something like "in the higher lever of GR, let us forget on principle of equivalence". How it is...

Is the motivation for the action principle purely from empirical evidence, or theoretical arguments, or a mixture of the two? As I understand it, there was some empirical evidence from Fermat's observations in optics, i.e. that light follows the path of least time, notions of virtual work and...

Let me start this question with a quote: "In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the...

why only the common tangential surface of the secondary wavelets forms the new wavefront ? what about all the other interferances that might occur between the waves of the secondary sources , like the constructive interferances that occur slightly offside towards the inside of the tangential...

Homework Statement Homework Equations PE at A = 3mgx WD = Fs KE = 1/2mv^2 The Attempt at a Solution The question I am stuck on is part ii. I worked out from part i that the PE at A is 3mgx, so therefore all this must go towards the KE and the sound, and doing work against friction, etc...

Homework Statement For the equilibrium reaction: ##Ag^+(aq) + Fe^{2+}(aq) \rightleftharpoons Ag(s) + Fe^{3+}(aq)\ \Delta H = -20 kJ## action that can be done so more silver get dissolved is ... A. Add FeCl3 B. Decrease the pressure C. Stir the mixture D. Add FeSO4 E. Decrease the temperature...

Frames under identical acceleration, regardless of whether due to gravity or accelerated motion, are locally identical but time runs slower in a gravity well. For example, at the center of a large mass (like the one pictured, below) time runs more slowly than for an inertial observer far from...

Homework Statement So as I understand, a negative Corona discharge happens between an electrode/pin/rod and a plane electrode. When the sharper electrode is connected to the negative (DC) plug, electrons concentrate on the tip, when sufficient breakthrough voltage is achieved a discharge...

Homework Statement Homework Equations Torque = F x D Manticlockwise = Mclockwise The Attempt at a Solution From what I understand, the moment on left hand side of the pivot point needs to be equal to the moment on right hand side, therefore... (Fx.2)+(5x.14) = (7xd) My initial...

When I'm solving a superposition principle problem i get stuck and so confused with the signs. For example this problem Consider three point charges at the corners of a triangle, as shown at right, where q1 = 6.00 × 10−9 C, q2 = −2.00 × 10−9 C, and q3 = 5.00 × 10−9 C. Find the magnitude and...

Homework Statement Reading Feynman The Principle of Least Action out of The Feynman Lectures on Physics, Vol 2. Link to text http://www.feynmanlectures.caltech.edu/II_19.html So I'm having a problem proving that, section 19-2 5th paragraf, that "Now the mean square of something that deviates...

Homework Statement i have a question on D'alemberts principle in which it asks me to find the velocity of a hammer immediately before impact with a pile the information i have been given is as follows: mass of hammer;300kg height of hammer;3.5m gravity to be taken as;9.81 mass of pile ;500kg...

I have read that the Schrodinger Uncertainty Principle is an extension of Heisenberg's. So, why don't we use the Schrodinger Uncertainty Principle instead of Heisenberg's? Thanks!

Hello everyone. I feel myself a little bit confused because I can't understand the difference between the working principle of the photodiode and the photoresistor. The photoresistor changes its resistance under the influence of light while photodiode changes the current across iself. Is this...

In the Infinite Square Well problem, an energy eigenstate is in an equal superposition of two momentum eigenstates with eigenvalues that are opposite in sign(like standing waves that are formed by two wavefunctions corresponding to "opposite momentums"). So, for every energy eigenstate, we...

Homework Statement Mercury is poured into a U-tube as shown in Figure a. The left arm of the tube has cross-sectional area A1 of 9.4 cm2, and the right arm has a cross-sectional area A2 of 4.50 cm2. One hundred grams of water are then poured into the right arm as shown in Figure b. (b) Given...

If we consider a system to undergo an irreversible process from state 1 to state 2 and a reversible process from state 2 to state 2, then through Clausius inequality (1to2∫dQirrev/T) + (2to1∫dQrev/T) ≤ 0 (1to2∫dQirrev/T) + s1 - s2 ≤ 0 s2-s1 ≥ (1to2∫dQirrev/T) Δs ≥ (1to2∫dQirrev/T) Does this...

When reading through one of the feynman lectures (http://www.feynmanlectures.caltech.edu/II_19.html) there was a paragraph that said: "In the case of light we also discussed the question: How does the particle find the right path? From the differential point of view, it is easy to understand...

This extract is taken from Sean Carroll's textbook. It talks about a theory that respects the Weak Equivalence Principle but violates the Einstein Equivalence Principle. we could imagine a theory of gravity in which freely falling particles begin to rotate as they moved through a gravitational...

Homework Statement The plano-convex lens has a diameter of 200 mm and the central thickness of 20 mm. The edge thickness is zero and the refractive index of glass is 1.5. Find the following parameters of the lens: (i) the back focal length Homework Equations N/A The Attempt at a Solution I've...

hello, everyone. When a vector field ##A_{\mu}## has the Lagrangian of the form as ##L=Const.{\times}F^{\mu\nu}F_{\mu\nu}##, where...

Homework Statement Just asking for a little help on this question 50kg object is pulled across a rough horizontal surface with a uniform force of 250N for 15m from rest, the surface has a frictional coefficient of 0.4, calculate the acceleration using dealemberts principle But this results in...

Homework Statement Homework Equations no equations required The Attempt at a Solution can someone please verify if my answer is correct. Thanks! I used the right-hand rule for the motor principle (although another tutor on physics forum told me that its supposed to be the 'left-hand rule'...

Homework Statement Homework Equations no equations are required The Attempt at a Solution is this correct? [/B]

Considering how Heisenberg's uncertainty principle is applied to a top-hat wave function: This hyperphysics page shows how you can go about estimating the minimum kinetic energy of a particle in a 1,2,3-D box: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/uncer2.html You can also...

I am aware that there have been a few posts about this, I read most of them so I just want to confirm that what I've picked up is correct. The principle of superposition only applies to forces that depend linearly on some quantity (charge and mass for example), and since we wouldn't know...

The Equivalence Principle says depicting gravity as a field associated with matter is equivalent to picturing it as twisting of space. Is there a space-twisting equivalent of a collapsed star as a shell of condensed matter with interior of intense gravitational field energy (found in the field...

Can anybody give me a simple example of uncertainty principle in both microscopic and microscopic level so that I can recall it every time I read about this topic ?

Let ζ5 be e2πi/5. Find a monic polynomial of degree two in K(ζ + ζ−1) So, if E/F is a field extension, with α∈E then K(α) = {f(x)∈F[x] | f(α)=0} and m(x) is the minimal polynomial of α over F such that K(α) = [m(x)] where [m(x)] is the ideal generated by m(x). I was thinking maybe (x- ζ -...

Is there an intuitive way to understand why nature selects the path that minimizes the action? I've seen it proven that the Euler-Lagrange equations are equivalent to Newton's laws (at least in Cartesian coordinates). So I can understand it mathematically. But on a more common-sense level...

Homework Statement Consider the linear system: dx/dt=x-y dy/dt=x+3y a. show that the function (x(t), y(t))=(te2t, -(t+1)e2t) is a solution to the differential equation (easy) b. Solve the initial value problem dx/dt=x-y dy/dt=x+3y y(0)=(0,2) need help with part b not a Homework Equations...

I heard the holographic principle is a sham and that there is no evidence to back it up and that 99% of physicists don't accept the idea as credible. Is this true?

I have a conundrum of sorts that has made me feel like an idiot and I am hoping someone can point out my mistake. Suppose a light source is placed to the left of a prism and a detector is placed on the opposite side. I have seen plenty of pictures of this sort, and they all appear to show the...

Homework Statement We have a system (see attached graphics) of two rods with length ##l## and mass ##m## and some external force ##F##. The coefficients ##k## of the two springs are given. The springs have no deformation when ##\varphi =0##. a) Find generalized force of the system. b) Determine...

There's something I don't manage to understand in the union between the relativity of simultaneity and the uncertainty of a quantum system's state. Observer A is in a lab on Earth. Observer B is approaching Earth at half the speed of light. On Earth, we build an experiment that gives a result...

Homework Statement (a) Show that in the Bohr model, the frequency of revo-lution of an electron in its circular orbit around a stationary hydrogen nucleus is f = me4/4ε02n3h3 (b) In classical physics, the frequency of revolution of the electron is equal to the frequency of the radiation that it...

Are physical constants, such as the elementary charge or the gravitational constant, subject to Heisenberg uncertainty principle, theoretically and empirically? Theoretically in the sense that infinite precision of these constants will directly violate HUP. Empirically in the sense that, for...

Hello Forum, What is the whole reasoning and importance of discovering that the inertial mass, which is introduced as the resistance to change the state of motion and the gravitational mass, which promotes motion (the larger it is the larger the attractive force). The equivalence principle...

Homework Statement A block of wood measures 2.2m by 2.5m with depth 3.6m with weight 102KN. When placed in water, how far will it sink? g = 9.81 ms-2 density of water = 1000kg m-3 Homework EquationsThe Attempt at a Solution Volume = 2.2(2.5)(3.6) = 19.8m3 Mass = 102000 / 9.81 = 10398 kg...

1. Homework Statement I have to demonstrate the Uncertainty Principle Starting from the expression of the following ket: |Ψa>=(ax^+ibp^)|Ψ> where a and b are complex numbers and the ^ denotes that x and p are unitary vectors. 2.Relevant equations I must use the bra-ket notation, but I...

I am trying to derive the geodesic equation using variational principle. My Lagrangian is $$ L = \sqrt{g_{jk}(x(t)) \frac{dx^j}{dt} \frac{dx^k}{dt}}$$ Using the Euler-Lagrange equation, I have got this. $$ \frac{d^2 x^u}{dt^2} + \Gamma^u_{mk} \frac{dx^m}{dt} \frac{dx^k}{dt} =...

Is Pascal's Principle valid with no gravity?

Huygens principle states that every point on a wave is a source of a secondary wavelet, so when you shine a light at a single slit, you get fringe patters. How come when you shine a normal light at a wall (without any slit), you don't get fringe patters? Surely, if every point on a wave is a...

Dear PF Forum, Determinism. 1. Is there determinism? 2. Because we can't measure the electron position, it doesn't mean there's no determinism? Heisenberg uncertainity principle states, per wiki: But because we can't measure it, it doesn't mean that the universe itself is indeterministic...

I wrote a blog post explaining the quantum pigeonhole paper (but critical of their interpretation of that result). As part of trying to improve at writing, I'm requesting criticism. What was confusing, what was good, what was rushed, what was wrong, etc. Also discussion about the quantum...

As I understand it, a Cartesian coordinate map (a coordinate map for which the line element takes the simple form ##ds^{2}=(dx^{1})^{2}+ (dx^{2})^{2}+\cdots +(dx^{n})^{2}##, and for which the coordinate basis ##\lbrace\frac{\partial}{\partial x^{\mu}}\rbrace## is orthonormal) can only be...

Homework Statement Please see the attachment for a better picture The energy of an electron in a hydrogen atom is: E = p^2/2m - αe2/r; where p is the momentum, r the orbital radius, me the electron mass, e the electron charge, and α the Coulomb constant. Use the uncertainty principle for...

How does the Pauli-exclusion principle explain ionization energy trends? Is it just that as you move down the periodic table, the electrons experience repulsion between each other, and thus the atoms get bigger?

What would the world be like if the Principle of Least Action were different? Let's say that it minimized a different quantity than KE - PE. EF Taylor et al argue that if the quantity minimized were KE + PE, physical systems would accelerate apart from one another. Here's their short articlet...

In page 15, Peskin and Schroeder states that The principle of least action states that when a system evolves from one given configuration to another between times ##t_1## and ##t_2##, it does so along the path in configuration space for which ##S## is an extremum. What is the definition of...