Position Definition and 1000 Threads

I have a question about the formalism of quantum mechanics. For some operator A... \langle x |A|\psi\rangle = A\langle x | \psi \rangle Can this be derived by sticking identity operators in or is it more a definition/postulate. Thanks.

Homework Statement The position of a ball moving on a straight line has an equation of p(t) = 1/3t^3 - 2t^2 +3t , where p is its position and s is time in seconds 1. At what times is the ball at rest? 2. Using its velocity and acceleration, determine the balls DIRECTION and if it is...

Hello guys! Lately I've been studying some topics in Physics which require an extensive use vector calculus identities and, therefore, the manipulation of partial redivatives of vectors - in particular of the position and velocity vectors. However, I am not sure if my understanding of partial...

Newton's laws says ## F=ma ##. Which, as far as I can see, states that all physical interactions concern the second time derivative of position. And because there is no other way for two bodies to interact in the physical world, the "worst" I can do to a system is change its acceleration, right...

Hello everyone. I'm new here and I'm not not a computer science student. But, I have to take programming to complete my degree. So, now I'm in a great depression about this assignment. My lecturer ask me to write a program to find root of an equation f(x)=0 for specific f. Both methods are...

I'm new to QM, but I've had a linear algebra course before. However I've never dealt with vector spaces having infinite dimension (as far as I remember). My QM professor said "the eigenvalues of the position operator don't exist". I've googled "eigenvalues of position operator", checked into...

Hi Everyone, This is my first post so bare with me. Firstly, a bit of background about the problem. I am designing a near rear drive train for a formula student car which incorporates a chain tensioning device linking the differential to the rear of the chassis. Essentially I am wanting...

Homework Statement A penny is released from the top of a very smooth sphere of radius 1.3 meters. The sphere is fixed to a platform and doesn't move. The penny slides down from rest and leaves the sphere at a certain point. How far will the penny fall away from the point of contact of the...

Homework Statement The position function of a particle is given by r(t) = <2t, 3, -2t+1> where t is the time in seconds. When is the speed a minimum? What is the minimum speed? Homework Equations v(t) = r'(t) The Attempt at a Solution The derivative of r'(t) = 2 + 0 + (-2) = 0. The t is...

Homework Statement Velocity vector given by r'(t)=<cos(t), -sin(t), -2sin(t)> Surface that the position vector needs to lie on: z=x2+y2 Homework Equations Integral of r'(t) will give position function The Attempt at a Solution I know that the integral of r'(t) will give me...

I've learned that there are three types of p shells, namely Px, Py and Pz, each in a different direction. I've also learned that when different atoms bond together, they form specific shapes depending on the number of bonds and electrons. I want to ask, will the shape of the p or d subshells...

The Canadian national men's curling competition (the Briar) is going on this weekend and I am motivated to write a computer program to simulate the motion of the rocks on the ice. I see on TV that the rectangular rink 14 by 126 feet appears to be trapezoidal on the screen, with the front about...

I recently read in a book that if i am standing on the top of a moving train and i jump in the air i will land behind my original position. But if i am inside the train and i jump i will land exactly where i was originally! Is this true?? And if it is, then why does this happen?

Hi there all, I have a personal project I'm working on and since I haven't done any linear algebra in many years I'm not sure what I think is right, is right. I'm also not entirely sure this is the right place to ask but I'm asking more for confirmation/clarification of methodology than...

x(t)=Acos(ωt+ϕ)\\ v(t)=-Aωsin(ωt+ϕ)\\ \\ Let\quad n=integer,\quad A=0.5,\quad ω=2.\\ \\ Given\quad initial\quad position\quad (0,\quad 0.25)\quad and\quad initial\quad velocity\quad (0,\quad 1),\quad find\quad ϕ.\\ \\ x(t)=0.5cos(2t+ϕ)\\ 0.25=0.5cos(ϕ)\\ ϕ=±1.0471975512+2πn\\ \\...

A stone is thrown upward from the top of a 20 m high cliff at an angle of 25 degrees. The stone has an initial velocity of 15 m/s. Make the BASE of the cliff the origin. (a) Write out the position, velocity, and acceleration vectors for the stone. (b) What is the magnitude of the velocity of the...

I graduated with a BA in physics in December 2012 in the United States and am currently searching for a job. I have a connection at a company that manufactures bearings, seals, and rings among other things for a variety of industries. Some examples of these industries are: medical systems...

I was given a table to plot on to a position time graph, but how would I know what type of motion to use? A curve or straight line? Here is the table T---P 0---0.0 4---2.0 6---3.0 10---4.0 15---5.0 16---5.0 18---4.4 22---3.2 26---2.0 28---1.4 33---0.0

Calculate electric field at position x given ρ and thickness d?? Homework Statement Two large uniformly charged slabs, I and II, are stacked together as shown in the picture. Suppose the thickness of each slab is d= 0.2 μm. The volume charge densities in the negatively charged slab (I)...

A particle of mass m moves in the x-y plane; its acceleration in m/s^2 is given by the expression ->a = −6iˆ for t ≥ 0 secs . At t = 0 secs, the object is at the point (x(sub 0), y(sub 0) = (36,0); coordinates are in meters. At t = 4 secs , the object is at the point x(sub 0), y(sub 0) = (36...

A hot-air balloon has just lifted off and is rising at the constant rate of 1.8 . Suddenly one of the passengers realizes she has left her camera on the ground. A friend picks it up and tosses it straight upward. If the passenger is 3.1 above her friend when the camera is tossed, what is the...

Hello! I was reading this excellent article about position independent code and it's implementation for shared libraries. I'm still confused about one part though. My current understanding is that the offset between the code section and data section is known at compile time. Since this offset...

Homework Statement A uniform rope of mass M and length L is pivoted at on point and whirls with uniform velocity ω What is the tension at the rope at r from the pivot point? Neglect gravity. Homework Equations The Attempt at a Solution Centripetal force at r is given by -mr...

Air traffic controllers usually describe the position of an aircraft relative to the airport by altitude horizontal distance and bearing . suppose an air craft altitude 1450 m , distance 24 km , and bearing 18.0 degrees east of north. what are the x,y,z components in meters of the position...

Homework Statement If ~r, ~v and ~a denote the position, velocity and acceleration of a particle, prove that Homework Equations (d/dt)[ a * ( v x r)] = (da/dt) * (v x r) "*" is a dot product "x" is a cross product The Attempt at a Solution I didn't really get that far. The...

Homework Statement We know, for constant n, \frac{\partial L}{\partial y} = \frac{d}{dx} (\frac{\partial L}{\partial y'}), where we define L as being the optical light path length, and y' is the derivative of y with respect to x, and L = L(y, y') = n \sqrt{1 + y' ^{2}}. However...

Hi. I am curious about ways to sense the position of a rotor in a BLDC motor. I am familiar with hall sensors and back emf but am wondering if there are other ways to find the position of a rotor maybe more accurately. I had an idea about using a laser and a photoresistor around the...

Hello, new to these forums! I'm working on my UPI homework, and I just want to verify if I'm doing something correctly. The problem: The position vector r of a particle moving in the x - y plane given by r = (2t^3)i + (6-7t^4)j, where r is in meters and t is in seconds. Calculate r v a...

I've read that if one wants to quantize gravity , there must be a smallest length scale " The Planck length " . If I want to measure the position of a point particle then in conventional Quantum mechanics I'll find it at the point $(x,y,z)$ at some-time $t$ with an arbitrary momentum but this...

A harmonic wave traveling in +x-direction has, at t = 0, a displacement of 13 units at x = 0 and a displacement of -7.5 units at x = 3λ/4. Write the equation for the wave at t = 0. Homework Equations The equation for a harmonic wave is r = asin(kx-vt+θ) a being the amplitude k...

looking for standards & guidelines on Neutral Wire for distribution system, especially Neutral Up or Neutral High (neutral on top of the phase conductors), advantages & dis-advantages of it.

We were told in lectures that the time independent Schrodinger equation can be applied to wavefunctions, i.e. \frac{hbar^2}{2m}\frac{d^2U}{dx^2}+V(x)U=EU where U is the wavefunction bra x ket psi. I don't understand why this is valid, as wavefunctions are probability amplitudes, and operators...

Determine the required angular velocity $\omega$ of the relative position vector in order to maintain a constant separation distance $r_0$ for two equal masses. What equations are needed for this?

I'm attempting SCIENCE by using math that I have never used before, nor do I understand (despite reading numerous articles, watching all of the khanacademy videos, etc etc) I'm attempting to use trig to locate a point directly behind another player in Minecraft. I've read through these...

According to the Copenhagen Interpretation, and considering Young's double slit experiment: Is what interferes the mathematical wave function flowing out the two slits but the electron itself takes a well defined path? Anyhow, I need a clearer idea about the position definition or...

Hey, My question is on determing the expectation value of position of the Harmonic Oscillator using raising and lowering operators, the question is part d) below: I have determined the position operator to be: \hat{x}=\sqrt{\frac{\hbar}{2m\omega}}(a+a^{\dagger}) and so the...

Relatively easy question but I haven't done anything like this in awhile. $$ \mathbf{r}(t) = \hat{\mathbf{x}}R\cos(\omega t) + \hat{\mathbf{y}}R\sin(\omega t) $$ The particle moves in a circle so I want to show that the position is given by the above. I know at $t = 0$ the particle is on the...

Homework Statement "On a certain clock, the minute hand is 8 cm long and the hour hand is 6 cm long. How fast, in cm/min, is the distance between the tips of the hands changing at 9 am?" Homework Equations The Attempt at a Solution I should be able to transform this somewhat...

Homework Statement compute the curl of: \vec{r} and \frac{\vec{r}}{r^3}Homework Equations \vec{r}=x\hat{x}+y\hat{y}+z\hat{z} r^3=(x^2+y^2+z^2)^\frac{3}{2} The Attempt at a Solution I figured out that the curl of \vec{r} = 0 as my book says it should be... however...I also need to prove...

Hello guys, the following problem I've had is from Beer and Johnston, Dynamics: Homework Statement At a distance R above the Earth's surface, a particle at rest is let go. Given the gravitational acceleration: a =-g\frac{R^2}{r^2} where r is the distance from the center of the Earth to the...

Homework Statement { y }_{ f }={ y }_{ i }+{ v }_{ yi }t+\frac { 1 }{ 2 } { a }_{ y }{ t }^{ 2 }\\ { v }_{ yf }={ v }_{ yi }+{ a }_{ y }t Derive { { v }_{ yf } }^{ 2 }={ { v }_{ yi } }^{ 2 }+2{ a }_{ y }({ y }_{ f }-{ y }_{ i }) 2. The attempt at a solution This isn't an actual...

This might be a silly question, but I'm not sure about the answer... Commuting operators have identical eigenstates. For example: energy and position operators seem to commute: [E,x] = Ex - xE = 0 Does it mean that position and energy operators share identical eigenstates? Because...

Assuming $$\vec{r_{a}}$$ and $$\vec{r_{b}}$$ is calculated from an inertial frame of reference. then for any two objects (named a and b) in a system of more than two objects, Is this the Newton's third law, $$\frac{d^{2}}{dt^{2}}m_{a}\vec{r_{a}}=-\frac{d^{2}}{dt^{2}}m_{b}\vec{r_{b}}$$...

There's a lot of pessimism about academic work here on physics forums which is probably legitimate. However, what I find odd is that it would seem that somebody with a lot of endurance and time, doing several post-docs, assistant professorships or research professor positions would eventually...

small engineering school? I currently attend Oakland University's PhD program. Formerly I was in a larger more well known PhD program but that didn't work out. I got sick and had to leave and decided to stay in my home state of Michigan for my PhD. My dream is to become an excellent...

Homework Statement A circuit shows a 10kΩ potentiometer with a 5kΩ load. Determine the position of the pot across point XX (taken across the 5kΩ load) when the voltage across the load is 3v Homework Equations The Attempt at a Solution I DONT HAVE A CLUE... Really stumped on...

I attached a graph of a potential energy vs. position graph. My question is, the relative minimum is characterized as a equilibrium point, but what is, specifically, is this type of equilibrium point--a stable, unstable, or neutral one?

Hello, I would like to know how to calculate (x,y,z) in the inertial frame at any given time, t for a body I am testing. On the body, I have one instrument that can give me (u,v,w) in the body frame, another instrument to give (roll, pitch, yaw) in the body frame, and yet another instrument...

Homework Statement A plot of Calvin's Mom's position vs. time is shown. Rank the acceleration of the five regions (e.g., A, B, etc.) from most negative to most positive See attachment! Homework Equations The Attempt at a Solution I think that b is the most negative and c is zero, a...

Homework Statement What is the expectation value of <p*x> aka the momentum times the position operator, for a particle in a box. Homework Equations Psi(x) = root(2/l) sin (n∏x/l) P= -ih(bar)d/dx X=x The Attempt at a Solution All integrals are from 0 to L I'm typing this on a playbook so I...