Classical Definition and 1000 Threads

I have a degree in Electrical Engineering and I want to learn classical mechanics in my free time. I originally planned to just learn out of a textbook, but I saw the university near me has a graduate course in classical mechanics this semester, and I am considering enrolling in the course...

Homework Statement Consider two objects with masses ##m_1## and ##m_2## exerting forces on each other with magnitude ##F##. If no other net forces act on the objects, they obey the equations of motion ##m_1\ddot r_1=F##, ##m_2\ddot r_2=-F## Show that the corresponding equations of...

Earnshaw's theorem http://en.wikipedia.org/wiki/Earnshaw's_theorem gives a straightforward reason why we can't have a static equilibrium for a system of point charges. For some time I've been trying to find out if anyone's worked out a similar proof for the impossibility of a dynamic...

According to Maxwell's Equations, the classical vacuum permittivity and permeability have a very important role: They determine the speed of light. But it seems like these two important concepts are not as precisely defined in the quantum world. Are there rigorous analogs of these two...

Hi everyone. I'm confused with the balance of energy in this situation (I'm comparing the mechanical energy, initially, at rest, at a height = h, and then, at the end, at height = 0). It doesn't seem to be fine, maybe I missed something. I'd appreciate some help - Everything is in the .jpg...

I was recently reading about quantum computers because I once asked a teacher with more experience in the field "What was the origin of the quantum speedup" with his answer being quantum parallelism, which I kinda understood at that time, but I forgot about it. So, the other day I was thinking...

Dear all, I'd like to know what is the place/use of complex variables (and complex analysis) in classical mechanics. By the way, is there any? Thanks for your help. Best regards!

I'm currently collating my own personal notes and would really appreciate some feedback on my description of the relativity of position and velocity in classical mechanics. Here is what I have written "Position is clearly a relative quantity as two inertial frames S and S' displaced by a...

What is the relation between classical from quantum vs measurement problem. On one hand they seem to be related on the other they seem to be of different nature. We always see our screens on front of us and not 100 meters away, that we say is classical object although the screen is a quantum...

The QED theories merely state that a photon has spin and momentum. Are there any reasonable mechanistic descriptions, perhaps in terms of variations of E and H beyond the infinite plane wave (which is also not helpful)?

This question is inspired by ephen wilb's https://www.physicsforums.com/threads/quantum-theory-of-others.816818/#post-5130620. In Bohmian Mechanics, everything is exactly as in classical probability theory. How, from the point of view of BM, does the measurement problem arise? Since the...

I have a question that's been gnawing at me recently. In classical physics, momentum is mass times velocity, which makes sense, take the mass of an object, calculate the velocity and you are left with a vector quantity of momentum. In quantum physics, we have momentum p=h/λ. This doesn't seem...

Homework Statement A stopping potential of 0.50 V is required when a phototube is illuminated with monochromatic light of wavelength 600 nm. Monochromatic light of a different wavelength is now shone on the tube, and the stopping potential is measured to be 1.1V. What is the wavelength of this...

Good afternoon all, A few days ago, I had been reading a book on general relativity and cosmology by Dr. Brian Greene, in which something was written that I found to be very profound. (At least, from the standpoint of my own ignorance on the subject.) I was wondering if any professionals could...

In QM there is no cloning theorem that says "we can't clone or erase quantum state". But in classical macro world we can copy information and erase it. If we should describe classical information as a very complex quantum state then we shouldn't be able to copy or erase it, right? And obviously...

In the quest of searching what are the basic ingredients of quantum theory that provide exponential speed-up to some quantum algorithms, a basic question that is pursued in the literature is when a quantum circuit (or algorithm) can be classically simulated efficiently. One example is this paper...

Hi there, I am confusing on the statement that we have classical physics when Planck constant approaching zero. I search the similar topic in Physics Forums and I saw that most of the answers refer to the size effect. It argues that when we measure something in the scale of meter comparing to...

There is only one way to reduce the equations of special relativity (aka Lorentz Transformations) to the equations of Newtonian mechanics (aka Galilean Transformations). In light of the above, why are there multiple ways to reduce quantum-mechanical equations of motion into classical equations...

Homework Statement I'm asked to calculate the propability of finding a particle outside the classical limit for a quantum harmonic oscillator in it's ground state Homework Equations Ψ0(x) = a*emωx2/2hbar When a = (mω/πhbar)1/4 The ground state energy E0 =hbar*ω2/2 The Attempt at a Solution I...

Hello Seniors, I have done BSc in Physics but couldn't take lectures of Classical Mechanics. I am Almost blind in this subject. Since it's a core course in Physics, so i need your help to understand the basics in this course. If anyone of you have any helping material/notes/slides etc which...

Hello all. I have almost finished chapter 4 on energy in Taylor's classical mechanics book. But in the last example in this chapter I got confused. Here it is: "A uniform rigid cylinder of radius R rolls without slipping down a sloping track as shown in Figure 4.23. Use energy conservation to...

I'm an EE major doing a minor in physics. I have to take a standard intermediate electromagnetism course from the engineering department (which is just a more applied version of the physics department course). To get my minor, I was thinking about getting permission to use this course as a...

Hello, PF, I'm going to be taking graduate CM next semester and the professor uses Landau's textbook instead of Goldstein, which I take is the usual text. What are the appreciable differences between the books and what kind of math will be needed? I have the basics-complex analysis, linear...

Hi, Assuming the electron is a sphere of finite extent, the classical electron radius is derived by equating the energy of the electric field with mec2. For the computation of the field energy, we have to assume a charge distribution. Both constant charge density and constant surface density...

Homework Statement The transition amplitude for the harmonic oscillator may be written as ##\langle x_2, t_2 | x_1, t_1 \rangle = N_{\omega}(T) \exp(i/\hbar S_{cl})##, where ##T=t_2-t_1## and ##S_{cl}## is the classical action. Let the wave function at ##t=0## be ##\psi(x,o) =...

[Mentor's note -- this post does not use the homework template because it was moved here from a non-homework forum.] ---------------------------------------------- Not sure how the extra velocity quantity appears after deriving both side of the velocity function to get acceleration. Please help.

I have read some parts of the book but noticed some errors that are to much for me to be uncomfortable for the rest of the book. Anyone encountered such problems with the book? Mainly, encountering too many errors? Even the errata in the publisher's site didn't gave sufficient corrections to the...

In many textbooks, the non-commutativity for the canonical pair is considered to lead to the major variaty from classical mechanism(CM) to quantum mechanism(QM), and change the Possion bracket into quantum commutator is a standard procedure called as canonical quantization. But in fact the...

I don't know very much about quantum mechanics, but if I'm correct, the future can not be predicted with certainty according to quantum mechanics. If this is true, how can we have formulas in classical mechanics that do predict the future with certainty?

Is quantum physics closer to the truth than classical physics, or is it just a different way of looking at the same problem? For example, the rules of baseball explain the behavior of baseball players better than the rules of football, and vice versa. The rules of these two sports are not...

Hello all. I know both books cover some different topics, but for the topics they share, which one do you think is better? I have checked the first chapters in both books, and, for the time being, I can't decide. So, if anyone of you have used these textbooks, maybe you can give me a piece of...

I seem to have two approaches that I've seen and understand, but I can't quite see how they relate. 1. Write a general time evolving state as a superposition of stationary states multiplied by their exp(-iEt/h) factors, and calculate <x>. We find that <x>=Acos(wt+b) as in classical physics (in...

As seen in the picture, this question is about an object moving in the x-y plane. But I don't get why in equation 8.9 the cross terms vanish? If anyone can help me, that would be really nice.

I would appreciate any help with the following question: I know that for relativistic field theories, the stress tensor can be obtained from the classical action by differentiating with respect to the metric, as is explained on the wikipedia page...

I'm wondering if it's possible to send a man to the moon using only classical mechanics. If not, where would the classical equations fail?

If i have a current of both negative and positive charges(i know that there is also current from only negative and only positive charges,i'm not confused) along an infinite wire of square cross-section,and the we put a homogeneous magnetic field normal to the current,then a Lorentz force acts on...

This is the Euclidean classical action ##S_{cl}[\phi]=\int d^{4}x\ (\frac{1}{2}(\partial_{\mu}\phi)^{2}+U(\phi))##. It would be nice if somebody could explain the structure of the potential. I don't understand why ##\phi## is used instead of a position vector ##\textbf{r}##. Also, how can...

Homework Statement A point particle of mass m moves on a frictionless surface. Its position can be described with polar coordinates r and phi. The particle is connected to the origin of the coordinate system by a spring with spring constant k and unstretched length zero, which provides a force...

I am a secondary student who is in grade 10, which means that I am only beginning to learn physics and calculus (e.g. Newton's Laws and Binomial Theorem). I have a passion for physics and has been getting relatively good grades but recently I started to lay my hands on Newton's Laws and I am...

Would it be possible to have a generalised equation for magnetic force of interaction between magnet-magnet and magnet-ferromagnetic materials maybe iron.

Homework Statement - The force acting on a particle m = 3kg is given by the following force equation: F = (v/9)(3 - x2), the particle begins at a position of x = 1m with a speed of v = 0 m/s at time t = 0s. Find the displacement of the particle at time t = 5 s. Homework Equations F =...

It is stated that classical states are robust against decoherence.. what would happen if classical states can decohere too? Or how do you imagine it for example occurring to a table.. How would the table look like if it suffers decoherence too? Would you fall down if you sit on one?

In classical physics , specifically in rotational mechanics we have concepts of torque , angular momentum and their extensions. We widely use them in problem solving but how were they defined , what was the basis of their definition , was all that purely experimental and most importantly who did...

Hello, I am taking an introductory class on non relativistic classical field theory and right now we are doing the more mathematical aspect of things right now. The types of differential equations in the function ##f(\vec{r},t)## that are considered in this course are linear in the following...

MIT: Thermodynamics (2008) This is part 1 of 36 in the video series. Click the youtube link to find the playlist to select another video in the series.

Hallo Everyone, What are the most important unsolved problems in Classical Mechanics especially related to mechanics of rigid body mechanics, deformable-body mechanics and, fluid mechanics.

Dear all, How to differ the classical pixel and quantum pixel? How to represent the quantum pixel in quantum mechanics language? Some useful references are welcome. Thanks.

I'm looking for history books on the beginnings of physics (mechanics, electromagnetism, etc) focused on explaining the evolution of the various fields that we have nowadays in physics more than trying to introduce them. For example, I'm looking for books that talk about how Newton discovered...

Let's say one has a passion for classical physics - he/she wants to learn all there is to learn about classical physics. Given that she/he has the intelligence and work ethic, does a passion for classical physics an indication enough that she/he should pursue engineering? Or could one love...

At most schools, physics majors are only required to take two semesters of classical physics (correct me if i am wrong), with the third semester of the same series being an introduction to modern physics. I understand that most physics majors are more interested in modern physics, but classical...