System Definition and 1000 Threads

In quantum mechanics if I repeat a measurement of the same observable in succession I get the same quantum state if it is not a degenerate state. If I make the system under consideration interact with another quantum system and meanwhile keep measuring it what happens? Does the system not...

Hi. I'm not sure where to put this question, thermodynamics or the quantum physics forum (or somewhere else). For a system in equillibrium with a heat bath at temperature T, the Boltzman distribution can be used. We have the probability of finding the system in state n is given by ##p_n =...

Will the probability to provide a negative value of a Sz 1/2 spin system always be 0? If lambda 1 = hbar/2 and lambda 2 = -h bar/2 ?

Example: 3/4 pvc in closed circuit with pump. Linear distance of pipe=30ft / head 8ft .... so not counting friction, what general description of force can describe what's required to make the liquid circulate?

Hi there, I hope that somebody can help me with this.. Any response is much appreciated! Let's have a vertical closed-loop system where the fluid circulates using the pump. The temperature in both sections gradually changes (the upcomer section is heated up) so that the densities, velocities...

As the title asks, does the invariable plane of the Solar system have axial precession? And if so, how much and at what rate? I have tried to find an answer to these questions for a while now, but still haven't found any. I recently asked on reddit too, which pointed me to some speculation...

If I know a person has exerted total force F with their legs and I’m interested in breaking down said force in smaller forces exerted for each involved muscle group - how can I do it? With a basic level of understanding of human anatomy I can divide the leg as a series of levers but how can I...

For this problem, The solution is, However, how do they know the block B will move up and block A will move down? The masses of each are not given so could be the other way round if ##m_b > m_a##? Also how do they know that if block B moves up by 1cm, block A will move down by 2cm? Many thanks!

In my system I am trying to represent two lenses. L1 with focal length f1=910mm and the other lens, L2 with focal length f2=40mm. These lenses are space such that there is a distance of f1+f2 between the lenses. I have a unit amplitude plane wave incident on L1. My goal is to find the...

Triggered by the restore data from a deleted file thread, I was thinking about what improvements have been made in file systems in the last 50 or so years, What was not present in Multics or ITS or early unix..." I'm not talking about capacity limits. At the birth of the PC, one could have...

Hi, I'm not sure to understand what ##| \phi_n \rangle = \sum_i \alpha_i |\psi_n^i## means exactly or how we get it. From the statement, I understand that ##[U,H] = 0## and ##H|\psi_n \rangle = E_n|\psi_n \rangle## Also, a linear combination of all states is also an solution. If U commutes...

I am looking for more books like this one: https://archive.org/details/MethodOfCoordinateslittleMathematicsLibrary Method of Coordinaes (Little Mathematics Library) by A. S. Smogorzhevsky I am also interested in papers if you can suggest any. I am interested in texts, that explore the idea of...

In his original 1905 paper “On the Electrodynamics of Moving Bodies” Einstein's concludes his thought experiment on the definition of simultaneity by stating “It is essential to have time defined by means of stationary clocks in the stationary system, and the time now defined being appropriate...

Hi everybody, I encountered a problem simulation of permanent magnets (PM) in Ansys Maxwell. There are many PM in my simulation and I need to define for each of them a proper coordinate system (CS). But I could only defined 255 CS. After that I can create new CS but It won't be possible to...

If I have been given a system of inhomogeneous linear ODEs, $$ \vec{x'} = \begin{bmatrix} 4 & -1 \\ 5 & -2 \\ \end{bmatrix} \vec{x} + \begin{bmatrix} 18e^{2t} \\ 30e^{2t}\\ \end{bmatrix} $$ I have found its particular solution to be: $$ 1/4 \begin{bmatrix} -31e^{2t} - 25e^{6t} \\ 85e^{2t} -...

For this problem I was very confused whether conservation of angular momentum should be applied to the person, the swing or the person-swing system. It seems to me that there is no net torque on any of the three systems I listed above. However, it seems that the angular momentums of the three...

For part (f) Solution is I don't understand why the bit highlighted in yellow is true. Would anybody be kind enough to help.

Entropy question. Take a finite number of identical atoms in a specific volume of space at a moment of time. Run two thought experiments on this system scenarios (both time independent) 1: expand the volume of space of the system instantaneously by a factor of 10. The fixed number of atoms...

As a retired physics professor with a long experience in complex simulation software for high energy physics experiments (e.g. the LHC) I revisited last July the n-body planetary simulations which I taught in an undergraduate physics course during the Spring 2017. It was then that the...

Hey, gotta do some explanation first: I assume you know how roulette works. (if you dont: ball is thrown into a pit and it can either land on red, black or zero, each having a certain likeliness to land there. you can bet on where the ball will land) let's assume unrealistically you have the...

For this problem, If we assume that x = 0 is where the spring connects to the wall, then the rest position of the mass-spring-electric field position is x = EQ/k and the max position is x = 2EQ/k. Is there a reason for the symmetry between the rest position and max position? (The symmetry...

I am using 2 lenses in a 4f configuration. The input is a large collimated beam (632nm). After passage through the 2 lenses the beams vertical dimension remains constant, however, the horizontal dimension get smaller, as if it is being focused only in the horizontal direction. Does anyone have...

How can we control the pressure of the water inside a closed loop system (chiller system for example)? Let´s say, we have a pump curve and an system resistance curve that can be modified (through opening or closing some valves) In everywhere, what I see is that the intersection of the system...

Ok, logically, it must be that the static friction force of block A equal to the force of gravity on block B, so mass of block A is: m_A * 9.8 * 0.30 = m_B * 9.8 m_A * 2.94 = 2 * 9.8 m_A * 2.94 = 19.6 m_A \approx 6.7 kg. However, when I look at block A individually, there is one thing...

Let E be a fixed immutable quantity. E can be freely exchanged between T and V, as long as $$T + V = E$$ 1. What does the quantity $$\int_x T - V $$ signify? What is the importance of this quantity? -------------------- Let E now be the budget of a factory. E can either be spent on T or V in...

Hello! If I have a 2 level system, with the energy splitting between the 2 levels ##\omega_{12}## and an external perturbation characterized by a frequency ##\omega_P##, if ##\omega_{12}>>\omega_P## I can use the adiabatic approximation, and assume that the initial state of the system changes...

The system is shown below. It consists of a rod of length ##L## and mass ##m_b## connecting a disk of radius ##R## and mass ##m_d## to a collar of mass ##m_c## which is in turn free to slide without friction on a vertical and rigid pole. The disk rolls without slipping on the floor. The ends...

Hi I'm wondering if someone can illustrate with an example what I bracketed in blue? I'm having a hard time visualizing how it is that the accelerations of the components are NOT necessarily equal to the components of the acceleration...Much appreciated!

For example, in the problem below, if the center of mass is chosen to be measured initially at the center of the left mass, then it must be measured from the same position after the collision. This gives an initial COM of, and finial COM of, Which gives their change in center of mass of...

Hello, I am working on a theory for a Great Pyramid power plant and I need some help understanding if my current hypothesis is even possible and how to calculate how much water will fill the upper structure. I believe the water system to work as follows: An aqueduct delivers a steady flow of...

How can I solve a system of equations with complex numbers 2z+w=7i zi+w=-1 I have tried substituting z with a+bi and I have tried substituting w=7i-2z but didn't get anything useful. Edit: also, I've tried, multiplying lower eq. with -1 so that I can cancel w but I get stuck with 2z and zi and...

When you write out the equations of motion for a system of two isolated charges, you can add both of the equations and get the increase in the particles linear momentum on one side. On the other side, you get the sum of all the forces between the particles. I understand that this sum of forces...

So i was able to solve the angular velocity part but i don't know how to find the velocity of centre of mass . For the first part i simply conserved momentum about COM because if i consider the particles as a part of the same system as rod the collision are internal forces . I am mainly...

I have read in some books and articles that the Dirac-Bergmann procedure to deal with constraints in phase space does not care about holonomic and Non-holonomic constraints, but I've been unable to find a single example. So, I wanted to test that assertion by solving a simple non-holonomic...

In both the cases 7 kg mass accelerates towards the right because of the 50N force. The unbalanced forces in both the cases are the force of gravity due to 5kg block and force of friction. Applying Newton's second law of motion to cases 1 and 2 yields the following results for acceleration...

Hi, Unfortunately, I have problems with the task 4 In task 3 I got the following $$ T_f=T_ie^{\Delta S_i - c_i} $$ Then I proceeded as follows $$ \Delta S = \Delta S_1 + \Delta S_1 $$ $$ \Delta S =c_1ln(\frac{T_ie^{\Delta S_i - c_i}}{T_1})+c_2ln(\frac{T_f}{T_2})$$ $$ \Delta S...

I used the regular way of solving problems with pulleys. I tried to find the tension forces, which must be the same in the rope, but I get it wrong

I suspect we can treat the L shaped rod as two rods and then find the com for that system and then find the com of the ball and that system

I am trying to solve this and get the equations of motion using the Lagrangian method. I could do all the steps but the equations (especially the third one) seems..weird. What am I doing wrong? Sorry if the equations aren't in their simplest form, they are pulled straight from Wolfram...

Hello, I have some trouble understanding the role of the sympathetic nervous system in vasoconstriction and vasodilatation of blood vessels, I searched and found contradicting resources, does anyone have the right answer?

Scientists find the source of one of the rarest meteorites to fall on Earth https://www.msn.com/en-us/news/technology/scientists-find-the-source-of-one-of-the-rarest-meteorites-to-fall-on-earth/ar-AA13ejQe Terrestrial modification of the Ivuna meteorite and a reassessment of the chemical...

How would one go about solving this for a and b given N, E and K? n(0) + n(1) + … + n(K) = N n(0)*0 + n(1)*1 + … + n(K)*K = E Where n(k) = InverseDigamma(Digamma(a+1)-b*k)-1

tried writing the x position as x = Acos(wt) (ignoring the phase) so that d2x / dt2 = -w2x Substituting that into the individual motion equations would get the required result for the individual masses, but I am not sure how to combine the equations to get the reduced mass

Hello everyone, This is a question related to a research article involving a chaotic system that required to be solved numerically. I was trying to employ one of the spectral methods to solve the two dimensional version of the so called Rossler chaotic system...

The idea here (as I'm told) is to use the boundary conditions to get a transcendental equation, and then that transcendental equation can be solved numerically. So I'm making a few assumptions in this problem: 1. The potential ##V(x)## is even, so the wavefunction ##\psi(x)## is either even or...

Would anyone verify whether or not I've formulated the proper Lagrangian here for the system above (the pulleys are massless, inextensible ropes of length ##L## and ##S##): $$\mathcal{L} = T - U $$ $$ \mathcal{L} = \frac{1}{2} m_1 { \dot l_1 }^2+ \frac{1}{2} m_2 \left( { \dot l_2}- {\dot l_1 }...

I know data is decentralized in TFS. But how does that makes data sharing difficult? We've got distributed computing for the similar purpose on different machines as well. I read a lot on this but failed to find any information regarding why it was not possible to share data in TFS as compared...

In《Introducing Einstein's Relativity Ed 2》on page 106"lowering the first index with the metric,then it is easy to establish,for example by using geodesic coordinates..." In 《A First Course in General Relativity - 2nd Edition》on page 159 "If we lower the index a,we get(in the locally flat...

I used m1=m2=15,0kg System: FBD: Note: I believe I have solved a) correctly and am more confused about b). a) I started with drawing the FBD. Knowing that the net sum has to be zero for the system to be at rest I used the left mass to find the tension on the rope: S1 = G1 = 15kg*9,81m/s2 =...

I'm studying theoretical mechanics and I kind of find the notion of a "mechanical system" very slippery, especially when it comes to constraints. Take an example : I know that when a system consists of N particles and p constraints, it has 3N-p degrees of freedom; this is the definition. Then I...