Physical Definition and 1000 Threads

Homework Statement Free body force diagram question, where I have selected the best answer but the diagram doesn't ring completely true (see diagram uploaded). I think mathematically the diagram is sufficient but it doesn't properly represent the situation. Do you agree? Homework EquationsThe...

I'm an attorney trying to invalidate a patent that I believe is directed to patent-ineligible subject matter. It's been an interesting exercise, and I'd love to hear other ideas/suggestions/etc. on how to approach it. At a high level, the patent claims certain structures with a certain...

Is wave a physical object or its just a model?

In ##2-2## scattering, the Mandelstam variables ##s##, ##t## and ##u## encode the energy, momentum, and angles of particles in a scattering process in a Lorentz-invariant fashion. ##s=(p_{1}+p_{2})^{2}=(p_{3}+p_{4})^{2}## ##t=(p_{1}-p_{3})^{2}=(p_{2}-p_{4})^{2}##...

I've been asked to replace a professor for a couple of classes in an undergraduate quantum mechanic course. I have to present some topics on angular momentum, including the addition of angular momentum. I have no problem with the general theory and can present it just fine. But I would like to...

my question is why physical quantities need a unit?

Homework Statement Is there a physical difference between the following wave functions? If yes, why? If no, why not? \Psi(x,0) =5e^{-ax^2} \Psi(x,0) =\frac{1+i}{\sqrt{3}}e^{-ax^2} \Psi(x,0) =e^{i\pi/7}e^{-ax^2} Homework Equations - The Attempt at a Solution They only differ in the...

How to submit paper to physical review letter? is there any specific criteria such as recomendation from expert? or can we submit without recomendation?

What are the physical significances of the eccentricity and of the semi-latus rectum of the orbital ellipse?

I just want to share my paper I recently wrote. I am trying to submit for publication: [Reference to unpublished paper deleted]

I'm new at this, trying to understand the overall picture of GR From what I understand space does not actually curve but rather test particles tracing out their world lines in Euclidean space as compared to ones tracing out their world lines near a source of gravity is the physical meaning of...

I am relatively well versed when it comes to systems of spin, or doing the maths for them at least, but am unsure whether all of the {L2, Lz, (other required quantum numbers)} basis eigenstates for a general system of n particles of spins si, where si is the spin of the ith particle, can...

Consider the 2-point correlator of a real scalar field ##\hat{\phi}(t,\mathbf{x})##, $$\langle\hat{\phi}(t,\mathbf{x})\hat{\phi}(t,\mathbf{y})\rangle$$ How does one interpret this quantity physically? Is it quantifying the probability amplitude for a particle to be created at space-time point...

[Mentor's note: This question was split off from: https://www.physicsforums.com/threads/meaning-of-physical-quantities-and-division.880214/] What does this differential "d" mean? Why say dE instead of E? or

I read this interesting thread trying to find an answer to my questions (and I got even more confused). I study radiometry units in context of computer graphics. I have a few questions, starting from the basic ones: 1. Following AlexS's note, why is speed=distance/time and not distance*time? 2...

What are the prerequisites to read this book? In the book he stated that there are no GR and QFT knowledge assumed but some people said that it is not true. Can anyone comment on this book? Thanks.

Hope we have some PVD specialists in the house :) we have a pfeiffer e-beam PVD in the lab which i use to deposit Ni and Pt thin films ( around 100nm each) on Si wafers. I have always had the problem of "Ni splashes" while heating the target ( with the e beam) which leads to a process stop (...

Do we have any examples of physical constants appearing in topics that are focused more on abstract mathematics? For example, do the values of the physical constants ever appear in the results of papers on mathematics that are not focused on direct applications to physics? Could they do so if...

Is the wave function physical ? I've searched for this on the web, and most people seem to agree that it does not represent a physical thing. It'd be just a probability distribution. There is still debate and uncertainty about that question though. What annoys me then is what about the observed...

[You don't need to read the whole thing, but I'd recommend doing so, because there are examples of my struggles somewhere in there, like specific problems.] Greetings as usual, It's me again. That hopeful physicist who somehow found himself at the wrong place with the wrong mind in the wrong...

So here is my question, and maybe I am not asking it right, but here we go: If electromagnetism prevents me from actually touching anything at a quantum level, how is it that I can get cut by a knife, or get a road rash falling off my bike? If the negative field of electrons that surround...

Hey everyone, I am a CS major, and part of my curriculum has me taking 2 sequences in various sciences. Initially I wanted to do physics & chemistry. I ended up taking Physics I, but am unable to take Physics II next semester due to scheduling conflicts; thus this summer I am taking the first...

http://arxiv.org/abs/1202.2115 I know Arxiv isn't a real journal, but this caught my eye. Is this a meaningful physical interpretation of the Riemann hypothesis? From what I understand, the zeta function can be modeled as a wave, but attempting to solve for the real part requires infinite...

Hi. In the derivation of the relativistic formula for adding velocities, the Lorentz factor drops out. Mathematically, the formula works for inertial frames with relative velocity c and even gives an answer to Einstein's famous question about what happens if you drive at the speed of light and...

I understand that if we have a quantum mechanical system, then its state at some given time ##t## is fully described by a state vector ##\lvert\psi(t)\rangle## in a corresponding Hilbert space. This state vector containing all possible information about the distributions (of all possible values)...

For example if we could bring a radioactive atom to absolute zero, would it still be subject to the random radioactive decay? Or would absolute zero inhibit the normal half-life decay of the element? Perhaps in other words, would absolute zero inhibit the elapsing of time?

Hey, This is my first post so I am hoping to do everything right :-) I do not understand the physical meaning of a complex wavenumber. I understand that, with a general approach u(x,t) = Re(A*[e][(i(kx-omega*t)]) and a complex wavenuber that the wave is decaying exponentially with x. What...

Homework Statement Question: What is the physical dimension of Probability Current for a particle in 1 dimension? (Quantum Mechanics) Homework Equations Quantum mechanical Probability Current: The Attempt at a Solution I know the physical dimension of mass, that is kg. If I know every...

Homework Statement To me it makes more sense to use force*time instead of force*distance. Because when you are aplying force to an object that isn't moving you're still wasting energy. Or when you push a weight over the same distance with little force or big force, the amount of energy wasted...

1. Homework Statement The violet sleeve has mass M and is free to move horizontally without friction. The green rod has mass 2M and length L and can rotate around a pivot on the sleeve without friction. At t=0, the rod is in vertical position and is rotating with angular velocity w. What are...

In the vector calculus course, I calculated integrals like, ##\int \vec F \times \vec{dr} ## Does this kind of integrals have physical significance or practical application other than Biot-Savart's Law?

I've read some articles online saying that the temperature is a measure of average kinetic energy of molecules so as the temperature increases, more molecules will bump into each other. However, I still don't quite understand why we feel hot when more molecules bump into each other. Is high...

The volumetric probability density function for the 1s orbital of the hydrogen atom has 1 peak, and it occurs at the Bohr radius. http://img1.mnimgs.com/img/shared/content_ck_images/images/probability%20density.png For the 2s orbital, it has 2 peaks, neither of which coincides with an...

Is there any alternative books that teach you how to just do the problems rather than emphasizing why, and is there any books that emphasize why in an easier format? Something like a "mathematical methods for dummies" book? This is the book I'm referring to (...

By physical form I mean stored chemical or actual be a physical thing you can touch. Yes I understand it already is a physical form in atoms but I mean is it possible to have a jar of heat.

Homework Statement We have a rod (length L, mass m) suspended at a point whose distance from the center of mass is a. 1) prove that (generally) there exist two values of a (a1, a2) for which the pendulum oscillates with the same period. 2) derive and explain: T = 2\pi\sqrt{\frac{a_1+ a_2}{g}}...

I understand this question is rather marginal, but still think I might get some help here. I previously asked a question regarding the so-called computable Universe hypothesis which, roughly speaking, states that a universe, such as ours, may be (JUST IN PRINCIPLE) simulated on a large enough...

Or is it a physical property of the quantum system? Or else? The Joint Committe fo Guides in Metrology: http://www.bipm.org/en/committees/jc/jcgm/ says that: "A physical quantity (or "physical magnitude") is a physical property of a phenomenon, body, or substance, that can be quantified by...

Must an initial state always be mapped onto exactly one final state and vice versa? Consider a slope that is shaped like a curvy "w". Releasing a ball from either end will result in the same final state where the ball is stationary at the highest point in the middle. So does it mean that...

Hey guys, so the other day I had a course about capacitive sensors and this thing below came up. The capacitive sensor is connected to the conditioner via two coaxial cables, the outer conductor of those cables are conected to a metallic casing which is also conected to physical ground. The...

Homework Statement I have doubt in calculating the permissible error. It goes as follows Measure of two quantities along with the precision of respective measuring instrument is A = 25.0 ± 0.5 m/s, B = 0.10 ± 0.01 s. A physical quantity C is calculated as C = A × B. What will be the value of...

Homework Statement I have doubt in calculating the permissible error. It goes as follows Measure of two quantities along with the precision of respective measuring instrument is A = 25.0 ± 0.5 m/s, B = 0.10 ± 0.01 s. A physical quantity C is calculated as C = A × B. What will be the value of C...

Hello Aren't all irrational numbers having an infinitely long decimal component? If so, how can any measure of a physical quantity be irrational? the decimal component is infinitely long..but the magnitude of the physical quantity surely isnt?

Hi. Can we infer something about physics from stuff like Vitali sets or the Banach-Tarski paradox? Maybe if we assume the energy in a given space volume to be well defined and finite, that there must be fundamental particles that can't be split, or that there must be a Planck length and energy...

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...

what can make a student unable to attend physical activities at school ? like , what are the physical illnesses that make one unable to play sports . thank you

Interesting new work on the link between quantum state vectors are physical states: Can different quantum state vectors correspond to the same physical state? An experimental test Daniel Nigg et al 2016 New J. Phys. 18 013007 Abstract A century after the development of quantum theory, the...

I'm looking for good examples of physical motivation for integrals over scalar field. Here is an example I've found: If you want to know the final temperature of an object that travels through a medium described with a temperature field then you'll need a line integral It appears to me that...

Homework Statement I have the following task: A chemical reaction 2 A(g) <-> B(g) + C(g) has an equilibrium constant defined by: ln=0.8+ 1050/T−1,3.105/T² a) What is K at 400K? Calculate ΔrG0 In a volume of 5L you get 2 moles of A and 0.5 moles of B. Reaction still proceeds at 400K. Consider...

Hello! In my course on physical transport processes time and again these type of equations, containing partial derivatives, appear: But how do you actually calculate such an equation? I know how to take the partial derivative from a function like x²tz³. Would it be that I am given a...