Position Definition and 1000 Threads

Hi, So I applied for a postdoc position for a research lab in France. In my cover letter to the PI (who's English) I wrote at the end: "I will call you next week to make sure that you received my CV. Thank you for your time and consideration." I received an acknowledgment of my application...

We know that the universe is expanding,but do we know from which point it is expanding outwards?

A circuit has a 10 kΩ potentiometer with a 5 kΩ load. Determine the position of the slider on the ‘pot’ when the voltage across points ‘XX' is 3 V. Think I'm there but not sure of my working out is excessive or I've taken the long route R1 in series with 2 resistors in parallel (R2 and...

Derivative: position, velocity, acceleration as functions of time? Homework Statement A 1.00 kg glider attached to a spring with a force constant of 25.0 N/m oscillates on a frictionless, horizontal air track. At t = 0, the glider is passing through its equilibrium position with a velocity...

Hi everybody, I'm planning a 2016 mission to the moon similar to Apollo 8 (Orbital mechanics homework). I decided to start from a equatorial parking orbit, and then to perform a plane change. The problem is that I obviously need to know the position of the moon's orbit plane, which, as you know...

.. Using Keplerian Elements Hi. Disclaimer: this is the first foray into orbits I've ever taken. I only did mechanics in university and haven't really touched it sincew. I'm busy coding a simulation of a solar system. I've managed to code a routine to calculate the position of a body along...

In what kind of cases do u we formulate the equation type x=Asin(wt+phi) or x=Acos(wt+phi)...and if for example we use it to define the position of some thing in motion when do we know when to use cos and when to use sin...?

The first thing I remember hearing about in QM was the time-independent 1-D schrodinger equation, Hψ = (\frac{-\hbar^2}{2m}\frac{d^2}{dx^2} + V)ψ(x) = Eψ(x) . This is an eigenvalue equation, the Hamiltonian operator H operating on the energy eigenstate ψ to produce the product of the energy...

Homework Statement Using the position space representation, prove that: \left[L_i, x_j\right] = i\hbar\epsilon_{ijk}x_k . Similarly for \left[L_i, p_j\right] . Homework Equations Presumably, L_i = \epsilon_{ijk}x_jp_k . \left[x_i, p_j\right] = i\hbar\delta_{ij} . The Attempt at a...

I'm looking at some code from a book that details uses the heliocentric position and velocity to compute an orbit of a meteor. See attached pages. At the top of the section at mid-page, page 37, he gives a source, Herget, 1953, Solar Coordinates 1800-2000. The book was written in the...

Homework Statement Give expressions for computing the matrix elements Xmn of the matrix X representing the position operator X in the energy basis (using eigenvectors of the Harmiltonian operator) Also told to consider the example of the harmonic oscillator where energy eigenvalues are...

I'm designing a 4-layer board with a couple of CPLDs and a uC. The top and bottom layer are for signals and the 2nd layer is ground and the 3rd layer is 3.3V. I'm placing a 0.1uF X7R Ceramic cap in 0402 package on every Vcc/Gnd pair. The thing that confuses me is that I've seen several ways...

Solar position and velocity vectors -- Use? What are the solar position and velocity vectors used for? A program I'm working with requires them to help construct the trajectory of a meteor. Do they somehow become useful in calculating the orbit of the meteor? Aside from their use, I'm...

Homework Statement The circuit (attached) shows a 10kOhm potentiometer with a 5 KOhm load. Determine the position of the slider on the 'pot' when the voltage across points 'XX' is 3V. Homework Equations Vout = Vin* (R2/(R1+R2)) The Attempt at a Solution Please see attachment...

Hello! Not sure if this should go here, but it's from a physics textbook. I was reading about charge by induction and the use of an Earth to achieve this. Here's a wonderfully detailed and exquisite image that took many laborious hours to construct. The red and black Earth's are not intended...

I would just like some clarification and some assertion that I've got the right idea. Please correct everything I say! For any observable A over a finite-dimensional vector space with orthonormal basis kets \{|a_i\rangle\}_{i=1}^n we can write A = IAI = \left(\sum_{i=1}^n |a_i\rangle\langle...

Homework Statement A simple pendulum consists of a bob of mass 1.8kg attached to a string of length 2.3m. The pendulum is held at an angle of 30° from the vertical by a light horizontal string attached to a wall. If the horizontal string is cut close to the bob and the pendulum swings down...

Hi, I'm trying to calculate a postion and velocity of a body over time using an integrator at each time step, I've only used simple integrators so far but I wanted to a better one that I've seen, RK4 - Runge–Kutta method, to calculate new values of position equation. I've been using the...

I am solving a Hamiltonian including a term \begin{equation}(x\cdot S)^2\end{equation} The Hamiltonian is like this form: \begin{equation} H=L\cdot S+(x\cdot S)^2 \end{equation} where L is angular momentum operator and S is spin operator. The eigenvalue for \begin{equation}L^2 ...

Homework Statement The position of a particle is given by x = (2 cm) cos 10πt, where t is in seconds. (a) What is the frequency? Hz (b) What is the period? s (c) What is the amplitude of the particle's motion? cm (d) What is the first time after t = 0 that the particle is at its...

Dear All, After long time, I have to start working again on basic physics for my application in one of our automotive project. Anyway, my problem is, I receive the angular velocity of wheel from external source like (say CAN bus) for every 10ms, now, I need to calculate the Angular position...

Im currently a junior physics major with an average gpa. I want to continue my education to the graduate level, and in order to better my chances of getting into a good grad school I really need to start focusing on getting some research experience. I have looked over some of the research...

A 1kg particle is in a potential given in joules by U(x)=4x2+5x-3, where x is in meters. The particle is initially at position x=1m and moving with velocity v=6m/s in the +x direction. Find the position when the particle first comes to rest. Here is my train of thought F(x)= -dU/dx...

Homework Statement Electrons moving initially at 2.4 X 106 m / s in a horizontal direction. They enter a region between two plates of 2 cm in length and are subjected to an acceleration of 4x 1014 m/s2, vertical and pointing upwards. Determine: a) the vertical position of the electrons as...

Homework Statement Three ice skaters are on a perfectly smooth frictionless lake. They are together at rest at the middle of the lake when they push off on each other. When skater #1 (m1 = 80 kg) is 6.00 meters EAST of the starting position, and skater #2 (m2 = 60 kg) is 6.00 meters NORTH of...

1. Show that the angle between two position vectors is equal to the angle between two instantaneous velocity vectors eg. v1 and v2 when v1 and v2 are conncected tail to tail in a uniform circle. No angles are given, it is just general. 2. Has to be proven without calculus. No information...

Starting with, \hat{X}\psi = x\psi then, x\psi = x\psi \psi = \psi So the eigenfunctions for this operator can equal anything (as long as they keep \hat{X} linear and Hermitian), right? Well, McQuarrie says that "the eigenfunctions of a Hermitian operator are orthogonal", which can be...

Why in my textbook does it define a velocity field as V = V(x,y,z,t) where x, y, and z are functions of time. I'm mixed up because if x, y, and z are functions of time, why does there need to be an additional time term t?

Why can an oscilloscope have the probes changed in position and have a dc current reading but not for an ac current? I put the oscilloscope leads with the probe at D and the ground side at A, and there was no waveform, why is this?

Homework Statement Two infinitely long current carrying wires run into the page as indicated. Consider a closed triangular path that runs from point 1 to point 2 to point 3 and back to point 1 as shown. Which of the following plots best shows B•dl as a function of position along the closed...

Hi there, I need a help. There're given 4 sensors (any kind of sensor which can transmit&receive signals in order to find a distance between another sensors around there). And we know the position of first sensor, say x1=0, y1=0, and have to find other 3 sensor's position. We can easily find...

1. The position vector of a particle at time t ≥ 0 is given by r = sin(t)*i + cos(2t)*j. Find the cartesian equation for the path of the particle. 2. I was told that the answer is: y = 1 - 2x^2 But I don't know how to obtain that solution. 3. r = sin(t)*i + cos(2t)*j At first I...

Suppose I have acceleration defined as a function of position, "a(x)". How to convert it into a function of time "a(t)"? Please give an example for the case a(x)= x/s²

Homework Statement A particle starts from the origin with velocity 5 m/s at t = 0 and moves in the xy plane with a varying acceleration given by a = (9*squareroot*t)j, where "a" is in meters per second squared and t is in seconds. Determine the velocity of the particle as a function of...

Homework Statement The force shown in the figure acts on a 1.7kg- object whose initial speed is 0.44m/s and initial position is x=.27m. Find the speed of the object when it is at the location x=.99m. At what location would the object's speed be 0.32m/s ? Homework Equations I know...

Homework Statement We just had a test in my calc 3 class, and I'm pretty sure my teacher has the wrong solution to one of the answers. The question is about finding the speed of a particle given a space curve function r(t) = (cos2t)i + (3t - 1)j + (sin2t)k. Homework Equations v(t) =...

Homework Statement For t < 0, an object of mass m experiences no force and moves in the positive x direction with a constant speed vi. Beginning at t = 0, when the object passes position x = 0, it experiences a net resistive force proportional to the square of its speed: Fnet = −mkv2, where...

Well, I know if both the position and momentum are in a simultaneous eigenstate then, theoretically, we would be able to measure momentum and position without changing the wavefunction. But, is there such an eigenstate out there? Any help is appreciated! (sorry if the wording is awkward)

Homework Statement The force graphed in figure is applied to a 1.8-{\rm kg} box initially at rest at x = 0 on a frictionless, horizontal surface. (Graph is attached) Homework Equations F=ma (?) The Attempt at a Solution Don't know how to relate speed to these two scalars..

Homework Statement The position vector of a particle is given by r= ihat(2t^3-21t^2+60t+10) +jhat(3/2)(t^2-10t+9) At what time, if any, is the velocity of the particle zero (ie what time is the particle instantaneously at rest) Homework Equations The Attempt at a Solution...

Homework Statement Using Heisenberg's uncertainty principle, calculate the uncertainty in the position of a proton moving at a speed of (5.00±0.01) x 10^4 m/s. Homework Equations Δx\geq \frac{h}{4mΔv\pi} The Attempt at a Solution x\geq (6.626*10^-34)/(4pi(1.6726*10^-24)(5±0.01 *...

Homework Statement The problem is number 11, the problem statement would be in the first picture in the spoiler. Basically, I'm trying to find if two operators commute. They're not supposed to, since they involve momentum and position, but my work has been suggesting otherwise, so I'm doing...

Homework Statement Show that \left\langlex|p|x'\right\rangle = \hbar/i \partial/\partialx \delta(x-x') 2. The attempt at a solution \left\langlex|p|x'\right\rangle = i\hbar \delta(x-x')/(x-x') = i\hbar \partial/\partialx' \delta(x-x') = \hbar/i \partial/\partialx \delta(x-x') For...

This is an assignment for a class titled "Intro to Scientific Programming" and it is a prerequisite for Computational Physics. Homework Statement Create a graph of the position of a damped oscillator as a function of time.Homework Equations The equation is x = A*e^((-b/2m)*t)cos(omega*t +...

Hi again. I'm trying to determine the position of an orbit's ascending and descending nodes here. I already have the Longitude of the ascending node, and a unit vector that points to it, so what I now need is a way to find out the actual distance of the node from the central body. More...

I need help with a very general question. I was asked to find the instantaneous velocity of a position time graph at .5 seconds. i know to do this i need to create a line that is the tangent to that point. Here lie the problem... how on Earth do i make that line, and how do i measure the slope...

Hi guys I posted a picture of the problem set and my work so far. I am on letter (d) of the problem set and I am stuck. I am 90% sure I have the formulas to solve (d) through (g) but I am not clear how. Can anyone give me a basic idea on what step I should take next? Problem set my work...

Hello, To let you know where I stand, I am aware of the formal quantum theory (Hilbert space formulation). As you know, it states that an observable is an operator, and that's fine. My question is the following: what is the concrete realization of a measuring apparatus? The theory says...

A rocket sled for testing equipment under large accelerations starts at rest and acceler- ates according to the expression a = (1.7 m/s3) t + (7.9 m/s2) . How far does the sled move in the time interval t = 0 to t = 1.9 s ?

Homework Statement I'm so confused about the question below,actually i cannot understand the problem at all.Could anybody help me out?Thank you Homework Equations Find the operator for position x if the operator for momentum p is taken to be (h/2m)½（A+B),with[A,B]=1,and all other...