Physical Definition and 1000 Threads

Homework Statement Find the period of a pendulum consisting of a disk of mass M and radius R fixed to the end of the rod of length l and mass m. How does the period change if the disk is mounted to the rod by a friction less bearing so that it is perfectly free to spin? The centre of the...

Hello. Im looking for a good scrap or junk yard that has good supplies for low prices, mainly electronics, science, aviation, military. Just a place that sells decent quality stuff that can be used for science related stuff. Like old radars, satellite dishes, monitors, medical electronics...

I've been trying for a long time to get an answer to the question, "What is the physics or mechanical explanation of contracting physical objects and the distances between them?" I understand that the phenomenon is theorized to depend on different observations from different frames of reference...

hi, please explain can by using suitable operator we can find any physical quantity- as by using hamiltonian on wave function we can find energies by the eigenvalues? thanks wasi-uz-zaman

Hi Does anybody know the physics meaning of the following equation \frac{\partial u}{\partial t}+\bar{U}\frac{\partial u}{\partial x}=D\frac{\partial ^3 u}{\partial x^3} Is there any physical system can be described by this equation? Thanks.

Physical Problem -- triangle as a pool table Hello, can you please help me? It is an irregular triangle as a pool table: At point A, there is a small billiard ball. How should the bullet hit, that it hits first the band 1, then 2, and finally with the band 3, after a shock again arrives...

Hi I am not sure what method to use when analysing the difference in values between physical measured data and modeled data. This is to do with measuring the energy deposited at a point in water from a beam of photons. I have a set of physical measurements obtained whilst varying the...

Why is "squaring" so significant when it comes to basic physical laws? Let me begin by saying I do not have a background in physics, or science for that matter! I just have an interest in things like cosmology and particle physics because I like to understand things. So my question is this...

Hi, Can someone double check I understand this correctly? The turbofan has lower specific fuel consumption because a gas's momentum is proportional to its velocity, whereas a gas's kinetic energy is proportional to its squared velocity. Therefore a turbojet can be made more efficient by adding...

1. Hi all, I am doing a practice exam attempt and I am stuck on this question: What is the physical interpretation of |ψ(r,t)| and |ψ(r,t)|^2? Can the wavefunction |ψ(r,t)| be measured directly? My attempt was: The Schrodinger equation describes the relationship between the energy...

Hey all, I starting to study QED along with a slew with other materials. (I read in the QED book and when I don't understand a reference I go to Jackson's E&M and work some problems out, it has been beneficial thus far!) Most of the topics are not too far fetched but I am struggling to...

Dear All, I wonder if there are any constraints about posting a paper draft on arXiv before the submission to PRB? If there is any legal constraints what are they? What other things which may affect the paper's publication? for example: Editors not feeling excited about the paper because it...

I came across a blog post or some internet page (probably a year ago now) saying that since the 1970s biological systems could be described purely in terms of physics. I tried searching for a decent text that describes biology and chemistry in terms of rudimentary physics but couldn't find...

Trying to understand what happens upon impact to the metal of a car that is stopped (Vehicle 1)when another car's driver's side rear (Vehicle 2) impacts the stationary car . Vehicle 2 is a heavier, larger car and is moving in reverse at approximately 10-15 MPH. The impact site on Vehicle 1 is...

We all understand what metres PER second (m/s) physically means... but, What I was wondering was what does a 'metre-second' actually mean? Or does it have a physical meaning at all! As an example: If we take the units for Dynamic viscosity we have: Kilogram per metre second ( Kg /...

I would like to simulate the Physical Layer of the Controller Area Network(ISO 11898) to evaluate the performance of the system under varying conditions(Temperature, Twists/turn, Length, Termination type, Unfitting Node Terminations, Interconnections, Splices, Unbalanced Loading etc.) I will be...

In the mathematics of Calculus, a basic requirement is that the system or function should be continuous. Until the discovery that matter is discontinuous, applying Calculus in Physics was reasonable. But why is it still applied almost everywhere in physics ? Won't such applications produce...

Hi, I understand that some physical quantities in electromagnetism are analogous to physical quantities in heat transfer. For instance, electric field is analogous to temperature gradient. I want to know which physical quantity in heat transfer is analogous to Inductance ("L") ...

Why can't low frequency or high frequency light enter my eye just like ordinary light? I imagine an ordinary camera should be able to detect light if it enters the lens, no matter the frequency. Am I under a misapprehension about cameras? Why can't the eye do the same? I know this is a physics...

Hello! Today I've learned that when a Van der Waals gas undergoes a free expansion, it cools down a bit. :bugeye: This is in contrast with the ideal gas in which case since it does no work and since the process is adiabatic, the internal energy of the ideal gas remains unchanged by the...

Hi everyone, I'm a new member but it's not the first time I look at the forum. Well, I don't know if this is the right section to post my question. I think it is related to quantum mechanics interpretation too. Anyway, let's have a look at my problem. I've computed cross section for photon...

Homework Statement Homework Equations N/A The Attempt at a Solution I am having trouble getting my head around these questions, the first part a) wasn't too tricky, I used the fact that eigenfunctions of a Hermitian operator \hat{O} are orthogonal and got my normalisation...

Quantum mechanics says that physical observables are self-adjoint operators. Is this correspondence a bijection, ie can we realize any such operator as a physical observable? There are obvious practical concerns with physically realizing certain contrived operators. But are there any...

Hello, I am confused as to the physical significance of the dot product of B and ds. Why would we evaluate this scalar product. My textbook has it on here without any motivation for it. Also, why is the analogous gauss' law used with flux, yet magnetic flux doesn't use amperes law?

what is it ? please explaining the physical operation of semiconductor diode (pn junction).

In special relativity we have the relation that for a free particle E^2 = \vec p^2 + m_0^2 and that also hold in relativistic free field theories (free Klein-Gordon etc) where one can show that we have a completeness relation 1 = \int \frac{d^3 \vec p}{(2\pi)^3} \frac{1}{2E_{\vec...

Question: does the physical curvature of spacetime ever "move"? Something isn't adding up with Einstein's theory--or, more likely, I'm just not understanding it correctly! How can we say that the curvatures of spacetime created by the presence of stress-energy is giving us a continuum? When I...

Does space have a physical role in the "jerk" of acceleration? This "jerk" that the great Einstein talks about in his book is really confusing me. Without space, there seems not to be a medium through which matter can move, thusing allow it (matter) to make sense of "force." I'll use one...

In my TD classes I have to deal with entropy. But what does it really mean? I know that it is the degree of disorder and the equation S=q/t. But what is this disorder? How can a physical system be aware of order and disorder since it is an abstract concept?They say that solids have high order...

We are learning about NMR and ESR right now. I know physical chemistry is a difficult topic to learn because there is a lot of background information that you have to be aware of in order to understand things. My professor does not reference these background topics, speaks with a strong...

Homework Statement Typical semiconductor fabrication technologies employ copper (ρ ~ 15.7nΩm; μr ~1) as the interconnect material. A process is designed for a clock frequency of 1GHz, has interconnect cross sections ranging between 35nm x 70nm and 0.18um and 90nm. Quantitatively determine...

After normalising a wave equation, let's say psi = A*e^(-r/a), and finding that A = +/- sqrt(2/a), what does this mean in terms of the physical significance of the wave? Would the wave just be a superposition of two waves with the two different A values?

I am very confused about the physical meaning of the concept "flux" I am really trying to understand what it means, what unit it has, but I keep reading contradicting definitions. So, on the one hand, I read that "...flux is defined as the rate of flow of a property per unit area, which has...

Hello, everyone. I am currently a junior [physical] chemistry major and am picking out my future upper division electives. I've narrowed them down to a handful of classes and what I'm looking for is just a little background information on them, which ones might be better than others, general...

Problem: Which of the wave functions shown might conceivably have physical significance? Solution: I have attached a drawing of the two wave functions. According to my book, the one on the right could have physical significance, while the one on the left does not. Can anyone explain why not...

From Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles, Eisberg-Resnick: "A physical example approximating the idealized situation represented by these wave functions would be a proton moving in a highly monoenergetic beam emerging from a cyclotron. Such beams are used to...

Homework Statement Explain the difference in the following properties of dimethyl ether and ethanol: 1) Solubility in water 2) Rate of evaporation Homework Equations The Attempt at a Solution 1) Due to the oxygen being bonded to 2 carbon atoms none of the hydrogen atoms in the...

Green's function?? Physical interpretation?? Hi friends.. Can anyone help me to understand the physical interpretation of the green's function with help of some physical application example such as that from electrostatic?? I am unable to understand what is meant by linear operator in green...

Homework Statement Two charged spheres are brought into physical contact with each other. Initially, the charge on the first sphere was 2.34 nC, while the charge on the second sphere was -3.23 nC. a) What is the final charge (in C)on either charge?(2A) b) How many electrons moved...

We recently had a long thread https://www.physicsforums.com/showthread.php?t=666861 about cases where raising and lowering indices isn't completely natural, i.e., where a vector "naturally" wants to be upper-index or lower-index. If you have a metric, then it's pretty clear to me what...

"Finally, discuss some physical limitations that might ..." Homework Statement Part (d) of problem 1 here: http://faculty.washington.edu/joelzy/402_502_W13_hw4.pdf Homework Equations I have (I(t) I'(t))T = cos(t/√(LC))k1 + sin(t/√(LC))k2, some k1, k2 ε ℂ2 for my solution and so I know...

Author: Morris Kline Title: Calculus: An Intuitive and Physical Approach Amazon link: https://www.amazon.com/dp/0486404536/?tag=pfamazon01-20 Prerequisities: High-School Mathematics Level: Undergrad Table of Contents: Why Calculus? The Historical Motivations for the Calculus The...

Author: Donald McQuarrie, John Simon Title: Physical Chemistry: A Molecular Approach Amazon Link: https://www.amazon.com/dp/0935702997/?tag=pfamazon01-20

Author: Robert Stewart Title: Introduction to Physical Oceanography Download Link: http://oceanworld.tamu.edu/resources/ocng_textbook/PDF_files/book_pdf_files.html Prerequisities: Contents:

what is physical and geometrical meaning of limits?

Let us denote by X^i=(1,\vec 0) the Killing vector and by u^i(s) a tangent vector of a geodesic, where s is some affine parameter. What physical significance do the scalar quantity X_iu^i and its conservation hold? If any...? I have seen this in may books and exam questions. I wonder what it...

Homework Statement Indicate which of the following expressions yield eigenvalue equations and identify the eigenvalue. a) d/dx (sin(∏x/2)) b) -i*hbar * ∂/∂x (sin(∏x/2)) c) ∂/∂x (e-x^2) The Attempt at a Solution I know that if the wave equation yields an eigenvalue equation, it will...

Author: Peter Atkins Title: Physical Chemistry Amazon Link: https://www.amazon.com/dp/0716735393/?tag=pfamazon01-20 Prerequisities: Contents:

Author: Mary L. Boas Title: Mathematical Methods in the Physical Sciences Amazon Link: https://www.amazon.com/dp/0471198269/?tag=pfamazon01-20 Prerequisities: Calculus Table of Contents: Infinite Series, Power Series The Geometric Series Definitions and notation Applications of...

I am a graduate student in physics. Can someone recommend a book that explores transport phenomena or diffusion from a physical sciences (instead of engineering) point of view? I would like that because I'm not dealing with industrial equipment and don't want to spend chapters wading through...