What is Position: Definition and 1000 Discussions

The missionary position or man-on-top position is a sex position in which, generally, a woman lies on her back and a man lies on top of her while they face each other and engage in vaginal intercourse. The position may also be used for other sexual activity, such as anal sex. It is commonly associated with heterosexual sexual activity, but is also used by same-sex couples.The missionary position is the most common sex position, but is not regarded as the most favoured one. It may involve sexual penetration or non-penetrative sex (for example, intercrural sex), and its penile-vaginal aspect is an example of ventro-ventral (front-to-front) reproductive activity. Variations of the position allow varying degrees of clitoral stimulation, depth of penetration, participation on the part of the woman, and the likelihood and speed of orgasm.
The missionary position is often preferred by couples who enjoy the romantic aspects of ample skin-to-skin contact and opportunities to look into each other's eyes and kiss and caress each other. The position is also believed to be a good position for reproduction. During sexual activity, the missionary position allows the man to control the rhythm and depth of pelvic thrusting. It is also possible for the woman to thrust against him by moving her hips or pushing her feet against the bed, or squeeze him closer with her arms or legs. The position is less suitable for late stages of pregnancy, or when it is desired for the woman to have greater control over rhythm and depth of penetration.

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  1. T

    Position in Motion: When to Use Cos & Sin in x=A*sin(wt+phi) or x=A*cos(wt+phi)?

    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...?
  2. J

    What is the connection between energy eigenstates and position?

    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...
  3. B

    Commutation relations of angular momentum with position, momentum.

    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...
  4. S

    Computation of Solar Position and Velocity Vectors (Meteor Orbit)

    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...
  5. L

    Change for position to energy basis

    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...
  6. S

    Decoupling Caps' Via Position

    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...
  7. S

    Solar position and velocity vectors - Use?

    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...
  8. R

    Position of slider on potentiometer

    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...
  9. N

    Earth wire position and charging by induction

    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...
  10. U

    Position and Momentum Operators

    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...
  11. J

    Speed of Pendulum Bob at Lowest Point

    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...
  12. M

    Using Runge–Kutta method for position calc

    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...
  13. Y

    Hamiltonian with position spin coupling

    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 ...
  14. L

    Position of a particle is given by x = (2 cm) cos 10πt

    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...
  15. Y

    Calculation of Angular Position from Angular Velocity

    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...
  16. T

    Advice on obtaining an undergraduate research 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...
  17. E

    Find position when a particle comes to rest from a potential energy function

    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...
  18. M

    Electrons: Position, Exit Angle, 2 cm Length Plates

    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...
  19. A

    Find Final Position of Skater 3 on Lake

    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...
  20. B

    Centripetal Motion Velocity vs. Position Angle Assignment

    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...
  21. R

    Do the eigenfunctions for the position operator form an orthogonal set?

    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...
  22. M

    Question About Position, Velocity, etc. Fields

    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?
  23. W

    Why can an oscilloscope have the probes changed in position and have a

    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?
  24. S

    Plots of B•dl as a function of position along the closed path

    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...
  25. T

    Relative Positioning of Sensors

    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...
  26. E

    Converting Position Vector vs Time to Cartesian Coordinates

    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...
  27. W

    How to convert acceleration as a funtion of position to a function of time?

    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
  28. S

    Velocity and position of the particle as a function of time

    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...
  29. M

    Force and position problem?

    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...
  30. T

    Finding speed from position equation

    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) =...
  31. C

    Integrating velocity equation to find position?

    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...
  32. romsofia

    Quantum state with well-defined position and momentum?

    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)
  33. C

    Relating position and force to speed

    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..
  34. B

    2d Motion, calculating time when v=0 from position vector

    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...
  35. G

    Heisenberg's uncertainty principle, find uncertainty in position

    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 *...
  36. K

    Commutation relation of operators involving momentum and position

    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...
  37. A

    Dirac Notation - Position and Momentum

    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...
  38. I

    Create a graph of the position of a damped oscillator as a function of time.

    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 +...
  39. T

    Position of Ascending and Descending Nodes

    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...
  40. S

    Finding the instantaneous velocity on a position time graph

    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...
  41. D

    Calc 3/Vectors/Finding when object is furthest from origin given position vector.

    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...
  42. N

    What is a position measurement?

    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...
  43. N

    Acceleration Position question

    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 ?
  44. Q

    What Is the Position Operator x When Momentum p Is Defined as (h/2m)½(A+B)?

    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...
  45. S

    How to describe position of our solar system to some ETI in other galaxy?

    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...
  46. A

    Acceleration from Position vs Time^2 ?

    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...
  47. T

    Position vs. Time / Velocity

    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...
  48. M

    How can you let Initial position and initial velocity be equal to zero?

    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?
  49. C

    Find the position of the center of mass of the binary star system

    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...
  50. H

    Difference between position time, velocity time and acceleration time graph

    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?
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