Position Definition and 1000 Threads

  1. T

    Derive the following kinematics equation using the position and velocity equations

    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...
  2. M

    Energy vs. position eigenstates

    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...
  3. A

    Newton's third law in terms of inertial position vectors for n-body system

    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, $$\frac{d^{2}}{dt^{2}}m_{a}\vec{r_{a}}=-\frac{d^{2}}{dt^{2}}m_{b}\vec{r_{b}}$$...
  4. Arsenic&Lace

    Endurance->permanent academia position?

    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...
  5. P

    Could I get a tenure track faculty position at a small liberal arts college or

    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...
  6. H

    Determine the position of the slider on the pot

    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...
  7. B

    Potential Energy vs. Position Graph

    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?
  8. J

    Determine position given linear and angular accelerations

    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...
  9. O

    How Do You Analyze Acceleration on a Position vs. Time Graph?

    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...
  10. A

    Expectation value of momentum times position particles in a box

    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...
  11. S

    Deriving Rocket's position from acceleration.

    Homework Statement There's a short introduction saying that honing missiles can determine their position by utilizing their acceleration, then the problem says: Suppose that the missile's acceleration obeys the following equations: \\ a_x = 0.8\\ a_y = -6.0 - 3.0t Knowing that, in t =...
  12. S

    Deriving position from a car's velocity equation.

    Homework Statement A driver sees the red light, and instead of braking the car, changes the gear to neutral. Suppose that velocity obeys this equation: v = v_0 * e^{-bt} Where v_o = 20 m/s and b = 0.150 s^{-1} a)Acceleration when time equals 0;(Answer:-3.0 m/s^2) b)Displacement when t=5.0...
  13. C

    Archived Atwood Machine, I determining position of the masses.

    Homework Statement I know how to do this type of problem, I'm just confused as to how to determine the distance the (4m) mass goes up . Homework Equations N/A The Attempt at a Solution So I was thinking that if mass (5m) and mass (3m) go in opposite directions then mass (4m)...
  14. B

    The relationship between Kinetic Energy and Position

    Task So I am writting a lab, and one of the testable questions required me to come up with a relationship between position and kinetic energy. In the lab a cart is released on a ramp and the end point of the cart is used as the reference point (h=0). We formed a position time graph and we...
  15. O

    Calculations for sun position follower

    HI I'm making a sun follower with a pic, and I need the formulas to calculate the position of the sun, I need to calculate azimuth angle and zenith angle (Is that enough to know at any time the position of the sun?). Thanks
  16. H

    Probability of n position occupied by atoms

    Homework Statement If you have atoms that are normally located at the normal lattice positions or at an interstitial position where energy >ε, how can I find the probability that n interstitial positions are occupied by atoms? If we were to use large N how can I find the fraction of...
  17. W

    Position and Velocity as a function of time

    Homework Statement At time t=0 an ant starts to walk from -2f to -f at a constant speed v. Show that the position (q) and velocity (u) of the ants image as a function of time is given by: q=(2f-vt)f/(f-vt) AND u = f2v/(f-vt)2 Homework Equations d(u/v)/dx = [V(du/dx)-U(dv/dx)]/v2...
  18. S

    An applied force varies with position

    An applied force varies with position according to F = k1 xn− k2, where n = 3, k1 = 2.4 N/m3, and k2 = 56 N. How much work is done by this force on an object that moves from xi = 5.13 m to xf = 28.2 m? Answer in units of kJ i keep using the integration equation: w = ∫f(x) dx where k1x^4/4 - 56x...
  19. T

    Position and angle of Earth/Moon/Sun and timing

    Hello all, I made an account here some time ago but hadn't got around to using it. I'd quite like to build a program for getting the angle of the Earth compared to vernal equniox (so I can convert from ECI to ECEF co-ordinates), angle of the moon relative to the earth, and angle of the sun...
  20. S

    Calculating Force to Hold Cylinder in Position

    This is a work related problem. I was calculating the amount of force required to hold a cylinder in a position when its Center of gravity is not at the center. Problem Background Assume a 60' long cylinder. Circumferential it is made of 8 sections. For maintenance purpose, one...
  21. T

    Minimum Uncertainty in Electron Position: Rectangular Wave in k-space

    Homework Statement In the case of an electron wave packet, the function A(k) has a rectangular shape, i.e. it is equal to A0 if k0-a<k<k0+a, and zero everywhere else. (a) Find the minimal uncertainty of electron position. (b) Find the electron wavefunction. Homework Equations ΔxΔp=h/4pi...
  22. G

    Tracking the position of trebuchet payload

    Homework Statement For the parts of the Trebuchet shown, develop expressions for the position, velocity, and acceleration, x, x', and x'' of the payload as a function of the arm angle θ and its derivatives θ', θ''. Use the vector tools in Mathematica to help develop the expressions...
  23. P

    Distance between two position vectors.

    Hi, Supposing the position vectors of two bodies A and B are described thus: A = (a1,0,a3) + (Va,0,0)t and B = (0,b2,b3) + (Vb,Vb,0)t, where Va, Vb are constant in time. How may I find the minimum distance between these two bodies? If the vectors are skew, then the distance comes out as...
  24. P

    HW Lab PHYS101: Net torque of pulley system and meterstick position balance

    THANKS, I ONLY NEED HELP #2 NOW, PLEASE 10/31/12 @ 9:10 pm bumpHomework Statement 1)If the fulcrum of a 0.1 kg meter stick was placed at the 40 cm mark and a 200 g mass at the 0 cm mark, would it be possible to balance the meter stick with a 200 g mass on the long side of the meter stick? What...
  25. B

    Energy, force, acceleration, and work with time dependent position

    Homework Statement A 4.00-kg particle moves along the x axis. Its position varies with time according to x = t + 2.0t^3, where x is in meters and t is in seconds. Find (a) the kinetic energy of the particle at any time t, (b) the acceleration of the particle and the force acting on it at...
  26. B

    MS to teaching position - options?

    I've just started an MS program in physics, and I don't really have a clear career goal. I have realized that many people pursue MS degrees so that they can teach in high schools or at city colleges, and these sound like good options to keep in the cards. What is the job outlook for people...
  27. Adoniram

    1-dimensional non-conservative force that depends on position?

    Homework Statement Does there exist a 1-dimensional non-conservative force that depends on POSITION (not velocity)? Homework Equations N/A The Attempt at a Solution I've given this a lot of thought, and I can't come up with anything! Friction doesn't work, etc... Any help would...
  28. W

    Uncertainty in position for eigenstates (Liboff 3.10)

    Homework Statement From Liboff edition 4: For the state ψ(x,t)=A exp(x-x0)2 / {4a2} * exp(ip0x)/hbar * exp (-iω0t) show that (Δx)2 = a2 then argue the consistency of this conclusion with the change in shape that |ψ2| suffers with a change in the parameter a Homework...
  29. F

    Calculating work with force and position vectors

    Homework Statement What work is done by a force \vec{F}=((2 N/m)x)\hat{i} + (3 N)\hat{j}, with x in meters, that moves a particle from a position \vec{r}1=(2 m)\hat{i} + (3 m)\hat{j} to a position \vec{r}2=-(4 m)\hat{i} - (3 m)\hat{j} Homework Equations Work=F\bulletd The Attempt at...
  30. O

    Relating change in time to change in position and velocity

    I was looking back at some homework solutions I've solved earlier this term and I ran across this equation: Δt = 2*Δx/(vf+vi) Which seems to translate to: Δt = Δx/vave Is this an actual way of finding delta t? I got the answer right, but I can not understand or find where I got this...
  31. T

    Mass-Spring Equilibrium Point: Affect on Position, Velocity, & Acceleration

    Somehow I have become confused about the different parameters of a damped mass-spring system that follows: my'' + cy' + ky = 0 When the mass-spring system is oscillating, but passing through its equilibrium position (y=0), the third term will be zero. And from the best I can rationalize...
  32. K

    Work vs Position: Force-Displacement Relationship

    Homework Statement 1. You create a plot and the linear trend is y = 3.75 x + 0.135. The plot is titled "Work [Joule] versus Position [meter]". Write the "physics" translation for this plot's trendline. Homework Equations y = 3.75 x + 0.135. Find physics equation. The Attempt...
  33. C

    Determine the magnitude of force at pin A as a function of position d.

    Homework Statement Refer to link for picture of problem. http://session.masteringengineering.com/problemAsset/1127894/8/Prob.5-29.jpg Determine the magnitude of force at pin A as a function of position d. The mass of the weight is 700 kg and d goes from 1.7 m to 3.5 m I have found Fbc...
  34. C

    Position vectors in different frames of reference

    Homework Statement I am doing a problem involving a man dropping a ball from the top of a mast of a ship at t =0 a height h above the origin of a ship's coordinate system. In the sea's frame of reference, the ship is moving with velocity u\hat{i} . The origins of these two frames...
  35. M

    What is the significance of V(0) = -j in finding position vector?

    Problem: Find position vector given a(t) [ look in paint doc] v(0) = i, r(0) = j I highlighted a portion in the paint doc that I have a question for. Why V(0) = -j + C? = i? Where did they get the -j?? Thank you.
  36. Shackleford

    Physics Physics Assistant position (radiation physics department)

    I have an interview with HR next Wednesday. After that, I'm supposed to meet with a few people in the department. I was told it would take about three hours. How should I prepare? I just graduated in May with a B.S. Math, Physics Minor. Here's the job description...
  37. B

    Help understanding position operator eigenfunction derivation

    I'm having trouble understanding the derivation of the the position operator eigenfunction in Griffiths' book : How is it "nothing but the Dirac delta function"?? (which is not even a function). Couldn't g_{y}(x) simply be a function like (for any constant y) g_{y}(x) = 1 | x=y...
  38. C

    Is Position Really a Vector in Classical Mechanics?

    Is the position a vector? Today I had a lecture on classical mechanics and the professor talked about vectors and how do we use them in physics to describe some physical quantities as velocity and acceleration. But he was very insistent about the idea that the position it is not a vector, that...
  39. N

    Thinking of withdrawing from a class and not accepting a research position

    Is it really that bad to withdraw from a class? I am taking 18 credits and I am taking the following classes: Computer Based Experimentation Classical Mechanics Multivariable Calculus Linear Algebra Computing for math & science Students in Transition Seminar I'm going to drop 1 class, computer...
  40. N

    Can Two Particles Occupy the Same Position in Quantum Mechanics?

    The Pauli principle say that many body fermi particle wave function is antisymmetry if we permute two particles.Then if the spatial wave function is antisymmetry,so there is not exist two particle occupy a same spatial coordinate at the same time.But I do not understand how about the circumtance...
  41. M

    Position and time interval of a particle

    Homework Statement The position of a particle moving along the y-axis has a position given by y = 0.20m + (8.0m/s) t - (10 m/s2) t2. is there any time interval during which the particle is not moving? Homework Equations The Attempt at a Solution I said No but I'm not sure why...
  42. H

    Position on the plane of a man

    Homework Statement An man starts on 0+0i of the complex plane. During the first walk step he moves a distance 1 to the right and lands on 1+0i. At each walk phase after this initial one the walk length decreases by a factor f<1 and he changes direction by an angle theta (measured from the...
  43. B

    Position ~ Time Graph vs Displacement ~ Time Graph

    1. Are these two the same? I'm not sure. Sometimes my teacher labels the Y axis with a Delta Displacement [E]. Other times it's just Position (M), so I'm not sure how to identify if we are finding Speed or Velocity. I'm just assuming they are the same. 2. Also, position is a Vector quantity...
  44. T

    How do we measure the position of a particle?

    I'd like to know with some precision how the position of a particle is measured. Just to focus the potential answers, I'd like to know some details of it because perhaps with that I could get a better understanding of some basic principles such us: 1) commutation relation of x and p 2) some...
  45. P

    Three balls are dropped, find position of each ball

    Homework Statement Ball A is dropped at t=0 from a window. At t=6, the ball hits the ground. Neglect air resistance for question a) Suppose that at t=1, Balls B and C are thrown vertically down from the same window. Ball C has a greater initial velocity than Ball B, as shown by their...
  46. A

    Evaluate a Particle's Position at Given Times

    Homework Statement The position of a particle moving along the x-axis varies in time according to the expression x = 3t 2, where x is in meters and t is in seconds. Evaluate its position at the following times. ( a) t = 2.30 s (b) t = 2.30 s + Δt (c) Evaluate the limit of Δx/Δt...
  47. K

    The commutator of position and momentum - interpretation?

    Hello friends! Im trying to get an geometric interpretation of QM and am now confused about the commutation relation between operators. Lets take momentum and position... sure, the fact that they don't commute show that we can not diagonalize them simultanesly. But what is the interpretation of...
  48. N

    Discover the Position of Planets in Our Solar System Using Math

    Hi everyone! I was wandering how can i find out which is the position of a planet relative to sun, in our solar system using the math?
  49. B

    Find the Position of an Orbiting Spacecraft

    Homework Statement Lets say that there is a small spacecraft (mass doesn't matter due to Earth's huge mass) orbiting Earth with a current distance from the center at 6,700,000 m. This whole problem is on a 2D plane with the spacecraft 's current position at (0,6700000). It's current...
  50. PerpStudent

    Rationale of the position operator?

    Why is the position operator of a particle on the x-axis defined by x multiplied by the wave function? Is there an intuitive basis for this or is it merely something that simply works in QM?
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