Mechanics Definition and 999 Threads

Homework Statement: A binary star system consists of M1 and M2 separated by a distance D. M1 and M2 are revolving with an angular velocity w in circular orbits about their common center of mass. Mass is continuously being transferred from one star to the other. This transfer of mass causes...

Hi. There is a worked example in this book on P168-169 titled "Chain on a scale". Two different ways of obtaining the solution are shown. I am confused about the 2 different methods. Method 1 equates the rate of change of momentum of the chain to the net force on the chain giving F. Method 2...

First off, I was wondering if the acceleration of the conveyor belt can be considered a force. And I'm not exactly sure how to use Newton's second law if the object of the forces is itself on an accelerating surface. Also, I don't know whether it rolls with or without slipping. I thought I could...

I tried to workout the problem but I find motion in different coordinates systems a bit weird at the moment, so only thing I could do is realize that the x component of ##\vec r(t)## is: $$vt +x_0$$ but for simplicity we will use the initial condition ##x_0=0## so that ##t_0## is the moment the...

The wave function described seems impossible. Wave functions have to be differentiable at all points, right? Otherwise they don't represent a physically realizable state. The wave function in the example isn't differentiable at x=A, the maximum point. Also, for problem (c), I know it's visually...

David Deutsch, a theoretical physicist, talks about David Bohm in his book "the Fabric of Reality": "[w]orking out what Bohm’s invisible wave will do requires the same computations as working out what trillions of shadow photons will do. Some parts of the wave describe us, the observers...

Does quantum mechanics follow causality, phase transition, critical point, symmetry, asymmetry, order, disorder, continuation, discontinuation, limitation, without limitation, convergence, divergence, similarity, hierarchical structure, singularity, plurality?

what is the practical application of engineering mechanics dynamics in civil engineering when civil engineers work on static analysis?

My professor will be using Huang's Statistical Mechanics next semester and I have been reading a lot of polarizing reviews. Does anyone recommend a book to read parallel to Huang's to better understand the material and that discusses the same topics in similar fashion?

Summary: (TL;DNR) What subject should I study next in the realm of physics, considering I am a beginner Hello I am visiting this forum because as a young kid that is trying to learn physics without a proper teacher I am quite lost. Not as in I don't understand the material, its more so I don't...

In Newtonian mechanics, conservation laws of momentum and angular momentum for an isolated system follow from Newton's laws plus the assumption that all forces are central. This picture tells nothing about symmetries. In contrast, in Hamiltonian mechanics, conservation laws are tightly...

According to general relativity, gravity is simply the side-effect of bending the geometry of space-time. As a thought experiment imagine a 3D image being projected from a 2D hologram - the distance between the actual 2D pixels in the 2D plane always remains constant, yet depending on the shape...

Probability density function plays fundamental role in qunatum mechanics. I wanted to ask if there is any analogous density function in classical mechanics. Obviously if we solve Hamilton equations we get fully deterministic trajectory. But it should be possible to find function which shows...

If Newton II is defined as ##\sum F = \dot{p}## and ##p = mv##, why do we consider Newton I as a separate law for cases where ##\sum F = 0##? Is Newton I really independent of Newton II?

How valid is the statement "It means physics is ultimately concerned with descriptions of the real world" in the realm of QM? Heretic question, what is "real" besides the outcome of the measurement?

I'm trying to understand some notes that I have been given on Matrix Mechanics, specifically how the matrix element comes about and builds a matrix which when used applies the effect of an operator on a wavefunction. But I'm having some difficulties following what's being done in the notes with...

The momentum operator for one spation dimension is -iħd/dx (which isn't a vector operator) but for 3 spatial dimensions is -iħ∇ which is a vector operator. So is it a vector or a scalar operator ?

Could one come to think that time is irrelevant in quantum mechanics? we know that the QM equations are written with the time variable, (schrodinger equation). Yet everything suggests that time is irrelevant, as the search for loop quantum gravity seems to indicate

Problem Statement: There is no precise problem statement since it's an homework to be done independently, but I will try my best to explain it concisely (I also apologize for my mistakes in English) : I want to reproduce the simulation of the model presented in the pdf file attached to this...

First F=m(x+2) Initial velocity is 2m/s find the relation between the time and displacement Second F=m(2v+3) Initial velocity is 3 m/s Find v(t) Please help me I tried but I can't finish it

Hello, I remembered once hearing of a must-have quantum mechanics book by Paul Dirac. I don't remember if it was his Principles of QM or Lectures on QM. Based on the table of contents, I believe it was the Principles of QM book; however, looking at both I was thinking about getting his Lectures...

The question doesn't specify whether we're talking about translation or rotational equilibrium, so I suppose it's both: In order for the body to have translational equilibrium: 60 N + F2 = 0 F2 = -60N However, in order to have rotational equilibrium: 60 N * 3m + F2 *8 m = 0 60 N * 3m - 60 N...

A lecturer today told the class that relativistic QM for single particles is flawed by showing us that for a state centered at the origin, it was possible that ##Pr(\vec{x}>ct)>0##. He said that this was down to the fact that we should be considering multi-particle states in relativistic...

Why aren't you guys discussing this? http://de.arxiv.org/abs/1405.1548 The paper is 259 pages. And it will take me a year to read it. The Cellular Automaton Interpretation of Quantum Mechanics doesn't use any wave function. Just please tell me. How does it explain for example the double slit...

i want to know what is the most suitable quantum mechanics that will enables me after studying it to answer these specific questions ? i mean based on the hardness of these questions ( what book would you suggest to study these subjects ) . and by the way what is the level of these QM questions...

Problem Statement: An oil with density 900 kg/m3 and viscosity 0.18 Ns/m2 flows through a circular pipe which inclines upwards at 40° to the horizontal. The length of the pipe is 10 m and the diameter is 6 cm. The fluid pressure at the lower end of the pipe is 350 kPa and the pressure at the...

I ran into this kind of expression for a sum that appears in the theory of 1-dimensional Ising spin chains ##\displaystyle\sum\limits_{m=0}^{N-1}\frac{2(N-1)!}{(N-m-1)!m!}e^{-J(2m-N+1)/kT} = \frac{2e^{2J/kT-J(1-N)/kT}\left(e^{-2J/kT}(1+e^{2J/kT})\right)^N}{1+e^{2J/kT}}## where the ##k## is the...

Hi, I have a question, why when we study the Delta-Function Potencial we can treat with ##E < V##, since the following relation says ##\frac{d^2 \psi}{dx^2} = \frac{2m}{\hbar^2} (V - E) \psi## And do not allow it? or it is just ##E <...

I've come up with the following causes: - air resistance - parallax - during the collision, some of the kinetic energy gets converted into thermal energy. - invisible deformations But I'm not sure which would be the biggest effect on the total momentum change. Are there any other reasons that...

Correct me if I'm wrong, but I think it is not possible to solve (1) with all the data that's given. As for (2), I have come up with the following solutions: (a) - The tension in the string acts as the centripetal force on the fuzzy dice (b) - The frictional force between the road and the car...

Are this 2 words have same meaning in Newtonian mechanics: More than 2 non-parallel forces and Coplanar Concurrent Force System?

I have a solution, However Cant understand 1 point.Now, This is the solution: ##N_2 l cos\theta + \frac 1 2 F_g l cos\theta - f_2 l sin\theta = 0## ## N_2(1 - \mu tan\theta) + \frac 1 2 F_g = 0## This is the the point that I don't like - yes it is less that 0, but it's even less that...

In the double-slit experiment when a detector was placed before the two slits, a 2 strip pattern was produced after the two slits. When there was no detector placed before the two slits, a different pattern was produced after the two slits. Why does the presence of a detector before the two...

Most of the cases when I see applications of statistical mechanics is when Fermi-Dirac or Bose-Einstein statistic are used in condensed matter or the equilibrium equation of neutron stars. Besides the Poisson-Boltzmann equation, I would like to know what are the modern...

1st page of Chapter 7, p.276, very last line, p=p'. I get that in Newtonian mechanics, the forces, times and masses are the same in two different inertial reference frames, but shouldn't the momenta measured be different?

I would assume that all the tension in the wire originates from the weight of the mass, and is equal to ##T=mg##, but that is incorrect. Forming a right triangle with a hypothenuse denoted by ##x## and applying Pythagoras theorem: \begin{cases}x^2=y^2+l_o^2 \\ x+y=l_o+\Delta l\end{cases} Solving...

See Peter Shor's comments here and here and Urs Schreiber's comments here.

I think the effective action should make sense also in Quantum Mechanics, not only in QFT. But I have never seen described in a QM book as such. Could there be a QM book that uses effective actions? Or maybe in QM effective actions are called another name? I think effective actions in QM could...

The solution to the problem simply states: "Use of mv^2/r = 2000. T = (2000 + 7500) = 9500N". I don't understand this solution. Nothing more is provided. I don't know how you are supposed to find the radius (in order to use the centripetal force formula) merely from the information provided...

I'd like to point to the book The Philosophy of Quantum Mechanics by C. Friebe et al., Springer 2018. It contains many topics usually underrepresented in foundational discussions of quantum physics, in chapters on many-particle systems and quantum field theory. It also has in its last chapter a...

So using conservation of energy where v0 = 7000 m/s $$ K_{i} + U_{i} = K_{f} + U_{f} $$ $$\frac{1}{2}mv^{2}_{0} - \frac{GMm}{R} = \frac{1}{2}mv^{2} - \frac{GMm}{r}$$ where R = the radius of the Earth and r = the distance from Earth's center plus the height its orbiting $$v =...

I'd like to draw attention to a very recent paper by Jürg Fröhlich, a well-known mathematical physicist from the ETH Zürich. It starts out as follows: Section 2 is titled ''Standard formulation of Quantum Mechanics and its shortcomings''. Surely @vanhees71 has very convincing reasons why this...

To find axial load , 5m / 6m = 0.83 Arc tangent , tan-1(0.83) = 39.69 Cosine of the force , Cos(39.69) = 0.77 Sine of the force , Sin(39.69) = 0.64 Axial load in the vertical direction , (200kN/m X 6 = 1200kN / 2 = 600kN + self weight of 6kN = 606kN) So 606kN X 0.77 = 466.62kN Axial load in the...

In a book it says that "we know of quantum phenomena in the electromagnetic field that represents a failure of superposition,seen from the viewpoint of the classical theory." I want to about what quantum phenomena is he talking about? This was from the page 11 of the book Electricity And...

Part (a) was fine. For part (b), I started off with finding the position vector of bird A and bird B after 4 seconds, and this was: Position vector of A after 4 seconds: -4i + 11j Position vector of B after 4 seconds: (-8 + 4p)i + (9+8p)j But after this I'm lost. Usually I'd have some idea...

In analogy to classical mechanics, I thought a good definition to "What does "solving a quantum mechanics problem" mean?" was to give the propagator (aka the Green function, or the 2-point correlation function): In classical mechanics, solving a problem means to give the path of the particle...

As shown in figure there's a homogeneous solid sphere. It is rotating about axis which is passing through point P directed perpendicular to the plane of paper. (In short like a pendulum). I'm neglecting gravity and assuming a force F which is directed perpendicular to the string. (The string...

Summary: How much weight can the bars support? Three one-meter-long bars with cross-section area A = 1 square centimeter support a rigid plate of weight W. For steel, E = 200 GPa and S = 400 MPa. Determine the maximum weight W the bars can support for three cases: (i) all three bars are...

I tried to solve it and I got that the forces on the cylinder A are: F_1= 58.8 and F_2=58.8 Cylinder B are: F_3=117.6 and F_4=117.6 Cylinder C are: F_5= 58.8 and F_6=117.6 Can someone help me with this?

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