Mechanics Definition and 999 Threads

Let's try to get into the looking glass of quantum mechanics together.

[Mentor Note -- Two threads on the same by the OP have been merged into one] I'm having trouble understanding the solution my professor gave me, in particular, the accelerations of m_2 and m_1. When my professor solved for the acceleration of m_2, he used a as the acceleration but when I look...

I'm confused on how to derive the multidimensional generalization for a multivariable function. Everything makes sense here except the line, $$ \frac{\delta S}{\delta \psi} = \frac{\partial L}{\partial \psi} - \frac{d}{dx} \frac{\partial L}{\partial(\frac{\partial \psi}{\partial x})} -...

Hello, Springer books are on sale this week so I wanted to buy some textbooks to support my studies and (eventual) future career. I'm an undergrad (in europe) and my courses next year will be QM, GR and statistical mechanics, so I was looking for books about these topics, but any suggestion on...

Is Quantum Mechanics a Probabilistic Forecast of nature?Someone I know told me their interpretation of QM is that QM only a probabilistic forecast of systems like electrons around atoms. I would like someone to analyse this interpretation and say if its valid or not. According to this person we...

For this problem, The solution is, However, I though dams were built to withstand the average force exerted by the water. Therefore, from ##PA = F## a larger width dam would have less force exerted on it due to the greater area so would not have to be as thick (less mass, and thus inertia)...

I'm guessing this question can be solved using the law of conservation of momentum Vi = 5 m/s (5 m/s) M = (4.33 m/s) cos30 M + V sinθ M I don't know what to do after this... I'm also not sure if I use the sin and cos correctly.

Hi. I looked everywhere for a specific book but I cannot find any pdf copy of it. The book specifics are below: Publication Name: Principles of Quantum Mechanics Author: Hans C. Ohanian Publisher: Benjamin Cummings Publishing Company ISBN-10: 0137127952 ISBN-13L 9780137127955 I would...

I have attempted but with no result.

Is my solution correct? (I only have answers to odd-numbered exercises.) Is it a good solution or have I overcomplicated things? (a) The forward force provided by the engine balances the air resistance force, so ##F_{engine}=F_{air} = \alpha v^2 + \beta /v{^2}##. Let ##W_{engine}## be the...

My final answer is different from the official one in the back of the book, and I can't figure out what I did wrong. This is my attempt: Let block 1 be the vertically moving block and let block 2 be the horizontally moving one. Also, let ##m_1 = 6.00 ~\rm{kg}##, ##m_2 = 8.00 ~\rm{kg}##, ##v_0...

$$ \frac{5E-3*v^2}{2} = (2 + 5E-3)(10)(0.2)(2) $$ v = 56.64 I just don't get how this is the wrong answer....it's just simple conservation of energy, right?

Looking for something else I just stumbled over this paper the declare as introducing a field they call "bayesian mechanics". I thought I would create a new thread for a change and just highlight this paper. It's the first time I've seen this from the authors so I don't have their full...

TL;DR Summary: Mechanical engineering,robotics,mechnics,dynamics Hi guys , I'm new to mechnics and I want to learn it for building robotic arm , but I find mechanics book topics somewhat difficult for me , what I need to learn to get started as I'm a highschool student with basic level math.

I am following [this YouTube lecture by Schuller][1] where he finds the appropriate formalism for the quantum mechanics in the physical curved space. Everything makes sense to me but at the very end I see that we find the pull backed connection one-form on the base manifold. He says to the end...

Starting from the Heisenberg equation of motion, we have $$ih \frac{\partial p}{\partial t} = [p, H]$$ which simplifies to $$ih \frac{\partial p}{\partial t} = -ih\frac{\partial V}{\partial x}$$ but this just results in ## \frac{\partial p}{\partial t} = -ih\frac{\partial V}{\partial x}## and...

Hi everybody. Some years ago I came across a video on youtube where they talked about an experiment with small and large envelops, when the small ones were placed into the large ones and then it resulted in something interesting. It might have been an instance of delayed choice, but I am not...

It this correct explanation why quantum is not valid for large object? Why would small object want to hide their information?

It is often argued that Dirac Equation is not valid as relativistic quantum mechanics requires the creation of antiparticles. But, there are also some arguments that suggest otherwise. For example, I saw Arnold Neumaier's website on this that there are multiparticle relativistic quantum...

Warning: Long post, apologies beforehand. So science/physics isn't my field of study or work, but am always fascinated by it (looking back, perhaps I should have went down that route). In any event, a few months ago I went to finally learn more about relativity after reading a discussion of...

Hello, I hope you are doing well. I had a question about the eigenvalue problem of quantum mechanics. In a past class, I remember it was strongly emphasized that the eigenvalues of an eigenvalue problem is what we measure in the laboratory. ##A\psi = a\psi## where A would be the operator...

How much statistical mechanics do I need to know to study QFT, astrophysics, black hole thermodynamics, and other advanced topics? And where should I study it in your opinion? So far I have only read Tong's notes however I don't think it is enough. Some quantum statistical mechanics is also...

I'm having trouble understanding how to find out whether or not a stationary point is a minimum and I'm hoping for some clarification. In my class, we were shown that, using Euler's equation, the straight-line path: with constants a and b results in a stationary point of the integral: A...

TL;DR Summary: Is there a mental model for setting up equations of motion and related mathematical equations when tackling mechanics problems? Hi there, I'm going through a first year mechanics textbook (An Introduction to Mechanics by Kleppner et al) from MIT OpenCourseware as I'm interested...

Do you know of any place where I can look up things about the momentum (linear momentum) in fluid mechanics? It's just that when I have a variable velocity and it has to be integrated, I don't quite understand how to do it. I have looked for videos and things and I can't find that they are...

Hi, i'm struggling with that problem , i need to find the distance that point N went down.My way of thinking is that the structure is twice not statically determined because of the beam MN and beacuse of the left support which is also unnecessary in order for equilibrium. My 2 equations of...

I was looking at an example of fluid mechanics and I don't understand this. Statement figures: CONTINUITY EQUATION $$\left. \dfrac{dm}{dt}\right]_{MC}=(\dot{m}_2+\dot{m}_3)-\dot{m}_1=0$$ $$\dot{m}_1=\dot{m}_2+\dot{m}_3$$ $$\rho c_1A_1=\rho c_2A_2+\rho c_3A_3$$ $$\rho c_1 h1=\rho c_2 a1+\rho...

In "QED, The Strange Theory of Light And Matter" Richard Feynman describes the probability path of a single photon emitted from a source, reflected from a mirror surface, and finally reflected to a probe detector. This path is the least time path relative to the probe/viewer, determined by the...

Hi, I believe that I have an acceptable level of understanding where SRT, GRT, QM and QFT come from. This is not true for me regarding the "good old stuff". Newton, okay, this is relatively (:wink:) clear to me but do you know something about the historical motivation for Lagrangian and...

Suppose I stood up and spun around in a circle for about twenty seconds and stop. Then, I ask my friend to look into my eyes (as I try to look into his). He sees my eyes go back and forth and back and forth (and I cannot stop that). I vaguely recall someone telling me there is a hair (or...

I was reading the oscillations chapter which was talking about how to solve linear differential equations. He was talking about how to solve the second order differential below, where a is a constant: In the textbook, he solved it using the method of substitution i.e guessing the solution...

I've just come across the following line while studying (Young & Freedman) and found it amusing. It sounds like a dirty family secret we discuss once and then should never mention again :biggrin:

[This is a continuation of OP's thread here: https://www.physicsforums.com/threads/satellite-mechanics-linear-and-rotational-momentum.1046963/ ] satellite mechanics: linear and rotational momentum I'm trying to better understand classical mechanics, and came up with a question: Say we have a...

So, in a rare instance I actually read APS News, I came across “New Experiment Suggests Imaginary Numbers Must be Part of Real Quantum Physics.” In November 2022, Volume 31, Number 10. Since complex numbers are isomorphic to a real 2x2 matrix algebra, I was confused how such a claim can be...

Hi, the task is as follows Unfortunately, I am not getting anywhere at all with task c. I have now proceeded as follows: I assume that the calculation takes place in the reference system of the sun. In the task the following is valid, $$\vec{v}_{si}=-s\vec{v}_p$$ I have now simply assumed...

Hi, I'm working on a problem where I need to find the different energies allowed for a potential, and I found this link https://quantummechanics.ucsd.edu/ph130a/130_notes/node151.html, which is similar of what I'm doing. I'm using mathematica to find the values of E. However, I'm not sure how...

Is the answer 0.748?

satellite mechanics: linear and rotational momentum I'm trying to better understand classical mechanics, and came up with a question: Say we have a squared satellite weighting 100kg, 1 meter on each side. it has a thruster on it's side, shown in picture thruster quickly ejects 100g of propellant...

Figure: My attempt at a solution: For the calculation of ##F_{DB}## we consider the equilibrium in the whole machine. $$\left. \begin{array}{r} h\rightarrow h=6\cdot \sin \theta +3=6,44\, \textrm{ft} \\ d\rightarrow d=6\cos \theta -1,5=3,41\, \textrm{ft} \end{array}\right\} \,\, \alpha =\arctan...

Hi I’m looking for a textbook that shows the derivations of equations such as the different forms of the schrodinger equation fully and step by step.

Mcauley's "Classical mechanics: transformations, flows, integrable and chaotic dynamics" has a very interesting table of contents, and it has a philosophy of approaching Hamiltonian flows and chaos without using the formalism of modern differential geometry. Unfortunately, after reading the...

hello, I read in a lecture paper about fluid mechanics that velocity is not related to viscosity, i found this odd and i think it is an error , can someone confirm that?

I have no idea where to start with this problem. I am interested in any hints, or ways to proof this. But i would especially like to know how the commutator is connected to the identity.

The official solution says ±25.4°, but I'm having trouble reproducing it. Here is my solution: 1) The components of the velocity of firework F with respect to the ground G in the moment of explosion are the following (Notice, I'm using sin, because the statement says 30.0° from vertical.)...

I am aware of the Newtonian model of Gravitation and I am interested in Relativistic Mechanics. I do not know anything about relativistic mechanics other than its more "accurate" at modelling gravitation and that it "reduces" to the classical formulation in some cases. I only want to be able...

I was not able to attempt since I don't know which formula or method can be used to solve the problem

I'm quite interested in the aforementioned topic, and would like to take a look at more literature about it, and to learn more about it, and would like to ask if you know more about it, or know interesting aspects about it, you can suggest the titles of the materials, or share the links to the...

Hi, I have hard time to really understand what's a stationary state for a wave function. I know in a stationary state all observables are independent of time, but is the energy fix? Is the particle has some momentum? If a wave function oscillates between multiple energies does it means that the...