Position Definition and 1000 Threads

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...

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...

Hi, I am wondering how to describe a position of our solar system to some other extraterrestrial intelligence in some distant galaxy to find us? Is it possible or not? i mean if such guidance exist for any galaxy or they have to track back movement of your probe or spaceship etc. and some...

Homework Statement http://img824.imageshack.us/img824/6466/31231242.png http://img835.imageshack.us/img835/5220/76022234.png It's a free fall problem and I have to calculate a = g Homework Equations g = (2*(d-(vi * t)))/t^2 g = (2d)/t^2 The Attempt at a Solution I've made a...

Homework Statement A motion detector transmits a click which is reflected off of a moving car. The echo is received by the motion detector after .0026 seconds. the motion detector sends out a second click .1 seconds after the first click. The echo for the seconds click is received after...

How can you let Initial position and initioal velocity be equal to zero? I understand that it will be zero at time = 0, but as time goes on from 1, 2 , 3 , 4 won't it change? I underlined that it in read in the picture?

Homework Statement A binary star system consists of a star P and a star Q, of mass 4.0 x 10^10 kg and 2.0 x 10^10 kg respectively, separated 6.3 x 10^9 m apart. Star P and Star Q move in circular orbits with their centers at the center of mass which remains at rest. Find the position of...

What is the difference between position time graph, velocity time graph and acceleration time graph and how would each of them look like when drawn?

Homework Statement The diagram (http://i83.photobucket.com/albums/j282/missingyoub4urgone/Physicsyahoohelp.png) tracks the location of an object moving in a straight line along the x-axis. When is the object (a) farthest from the origin, (b) at rest for an instant, (c) in the midst of being at...

Homework Statement I can't figure out part two to a problem. The first part asked us to find the displacement, but I'll let you read for yourselves: Part 1: A cyclist maintains a constant velocity of 5.3 m/s headed away from point A. At some initial time, the cyclist is 259 m from point...

Homework Statement The position v. time graph for a certain object moving along the x-axis is shown. I don't have the graph. Bu I have the points. (0,-2), (1,9), (4,4), (6,4), (8,-4), (9,0) The object's initial position is -2m. Find the instantaneous velocity at ... (m/s) a.) 0.5s...

Hello, As a concrete model to refer to, I'll work with the one-particle system in a potential box with infinite edges. Inside the box is a potential barrier of height V. Let's say we've measured the energy at one moment to be E < V. The probability of measuring the particle inside the barrier...

Homework Statement A particle's trajectory is described by x=((1/2)*(t^3)-2t^2)m and y=((1/2)*(t^2)-2t)m, where t is in s. a) What are the particle's position and speed at t=0s and t=4s? b) What is the particle's direction of motion, measured as an angle from the x-axis, at t=0s and...

Hello everybody, I'm working on a project and I want to verify a few theories I have. I'm unfamiliar with equipment for taking these types of measurements, so I wanted a little bit of help on this. Basically a bb is fired from an airsoft gun (350-550 fps), and I want to find the...

two particle of mass, find distance of equilibrium position? need a hint to start question, really appreciate

Homework Statement An electric point charge of Q1 = 5.23 nC is placed at the origin of the real axis. Another point charge of Q2 = 1.89 nC is placed at a position of p = 2.63 m on the real axis. At which position can a third point charge of q = -2.62 nC be placed so that the net...

Homework Statement The acceleration of a particle is given by a(t)= - 2.1 m/s2 + (3.1 m/s3)t Find the initial velocity v0 such that the particle will have the same x-coordinate at time t=3.96 as it had at t=0. What x-coordinate will the particle have at time t=3.96 Homework...

I have read that, in QFT, unlike QM, there is no position probability density function because position is not considered an observable. Then how is a position measurement represented/modeled in QFT? As always, thanks in advance.

Confused about a simple thing... For a common balance, since both arms have equal weight, what causes the pole to choose a horizontal position? Shouldnt it be stable in any other position as the torque around the centre is zero for any other position too?

The position of an object is given by x=At+Bt^2, where x is in meters and t is in seconds. a)What are the units of A? (express answers in terms of m and s) b)What are the units of B? (express answers in terms of m and s) I know this may sound silly, but I really don't understand what the...

I just started taking a Quantum Mechanics course at my university (only 3 days into it) and some of the topics got me thinking about stuff. Namely, about "particles". I searched on Physics Forums and found some other posts pertaining to my question, but a lot of the responses referenced topics...