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. S

    Time dependent position given position dependent force

    Homework Statement A particle of mass m is subject to a force F(x) = −kx^−2 (1) that attracts it toward the origin. (a) Determine the potential energy function U(x), defined by F(x) = − d U(x)/dx. (b) Assuming that the particle is released from rest at a position x0, show that the time t...
  2. K

    Gaussian wave packet in position space

    Hi all, The Gaussian wave packet is widely discussed in the text. I got the following expression for wave packet in momentum space ##\psi(p, 0) = A \exp\left[-(p-p_0)^2/ (2\sigma_p^2)\right]## with ##A=\sqrt{2\sigma_p/\sqrt{2\pi}}## As my understanding, the corresponding wave packet in...
  3. Gh778

    The position of a point in 2 rotations with 2 axes

    Homework Statement It's a question I ask to myself. A support turns at ##w_0## and can accelerate. A disk on the support can turn around itself (side view) but at start ##w_1=0##. I done the experimentation with 2 wheels but I'm not sure about my tests. There is an angle between 2 axes: The...
  4. Adoniram

    Finding most probable position for given wave function

    Homework Statement A particle has a given wavefunction: ##ψ(x) = C e^{-x}(1-e^{-x})## (many steps in between) ... Find the most probable position of the particle Homework Equations Most probable is where the probability density's derivative = 0. Right? ##P(x) = |ψ(x)|^{2}## The Attempt at a...
  5. Andre' Quanta

    The operator X for the position in QFT

    During a course of QFT my teacher said that in this theory is not possible to use the operator X for the position in order to construct with the momentum P and the spin S a set of irreducible operators that charachterize particles, and that we need a different point of wiev: the irreducible...
  6. G

    Uncertainty principle if position is restricted

    Hi. Assume we have a large number of identical boxes of some finite length ##l## and with infinite potential walls. Let's prepare them all in the same momentum eigenstate. Since for eigenstates ##\Delta p=0##, by the uncertainty principle ##\Delta x## should go to infinity. However, since the...
  7. J

    Engineering How hard to get an entry chemical engineering position?

    I am a nontraditional applicant with a bachelor's degree in neuroscience. I am almost finished a master's degree in chemical engineering, but many jobs that I wish to apply to have a "bachelor's of engineering" as a requirement. And a master's as only a "preference." Would these companies still...
  8. B

    Identifying Increasing Speed from Position vs. Time Graphs

    Homework Statement Three objects can only move along a straight, level path. The graphs below show the po- sition d of each of the objects plotted as a function of time t. The magnitude of the velocity ∥⃗v∥ of the object increases in which of the cases? (view image/attached file) Homework...
  9. R

    How do robotic arms/joints know what position they are at?

    I guess I am interested in the various electronic means of finding out how a robotic joint relays positional information back to it's control unit.
  10. M

    Table for signs of position, displacement, and velocity

    Homework Statement Homework Equations Velocity = Displacment/Time The Attempt at a Solution Ok, so I thought this was straightforward at first, but I'm having my doubts. The position column, I filled out with the standard assumption the right and up are positive and left and down are...
  11. A

    Force and momentum in gymnastics position

    Hi. I'm trying to solve this problem but I'm not sure my solution is right: "Suppose that a male gymnast wishes to execute an iron cross during a gymnastics session. The total mass of the gymnast is 60 kg. Each ring supports half of the gymnast's weight. Assume that the weight of one of his...
  12. bcrowell

    Educational app for graphing position, velocity, and accel

    I thought other physics teachers here might be interested in this browser-based educational application I wrote: http://www.lightandmatter.com/velocity/ . As you move the mouse up and down, it graphs its position, velocity, and acceleration. In the past I've had some classroom exercises that...
  13. ZapperZ

    Insights Postdoctoral Physics Position - Comments

    ZapperZ submitted a new PF Insights post Postdoctoral Physics Position Continue reading the Original PF Insights Post.
  14. Shailesh Pincha

    What are the failed experiments to determine electron's position?

    What are some of the failed experiments to determine electron's position? One could be by electromagnetic radiation of suitable wavelength (here X rays) but that tears apart the atom. I want to know the different views tried to determine electron position.
  15. F

    Heisenberg Uncertainty in wavelength and position

    Homework Statement Show that ## \Delta\lambda\Delta\ x>lamdba^2/4*pi## The Attempt at a Solution When I substitute de Broglie's p=h/lambda I get the equation of ##\frac {\Delta\x}{\Delta\lambda} > 1/(4*pi )##
  16. N

    Understanding Position-Time Graphs: Can They Determine Speed?

    Can the position-time graph tell you the speed? I thought it was ONLY velocity. Can you please give me an example when IT DOESN'T allow you to find the speed? Thanks so much in advance!
  17. D

    Quantum oscillator from position to momentum space

    So I've read you can get the corresponding wave function of a quantum harmonic oscillator in momentum space from position space by making the substitution ##x \to k## and ##m \omega \to 1/m \omega##. However in deriving the TISE for momentum space, I seem to be making a mistake. In momentum...
  18. H

    B Why is the uncertainty in position equal to the wavelength?

    Why is the uncertainty in position of an object which is determined by a wave equal to the wavelength of the object? I don't get it. Isn't the wave diffracted at the surface of the object? we can then calculated the distance from velocity and time accurately, can't we? is it because we must...
  19. twoski

    Get vector position projected on line

    Let's say i have a set of lines (denoted in the image as connected at the blue dots) and a rectangle with maxs and mins known (denoted with orange dots). I want to project from the mins of my rectangle such that i get a point on the line below it (the green dot). Furthermore, this needs to be...
  20. H

    Hamiltonian in the position basis

    According to <x|H|x\prime>=(-\hbar ^2 /2m \frac{\partial^2 }{\partial x^2}+v(x)) \delta (x-x\prime) can one draw the conclusion that the Hamiltonian is always diagonal in the position basis?
  21. Fantini

    MHB Relation between matrix elements of momentum and position operators

    Hello. I'm having trouble understanding what is required in the following problem: Find the relation between the matrix elements of the operators $\widehat{p}$ and $\widehat{x}$ in the base of eigenvectors of the Hamiltonian for one particle, that is, $$\widehat{H} = \frac{1}{2M} \widehat{p}^2...
  22. H

    How to prove that position by velocity is a constant vector

    [Note from mentor: this thread was originally posted in a non-homework forum, therefore it does not use the homework template.] ------------------------------- So I've been asked to prove that in a harmonic function where a(t)+w2r(t)=0 that (1) v(t).v(t)+w2r(t).r(t)=constant scalar and...
  23. L

    Position of unknown material on electrostatic series?

    Homework Statement You have a new unknown material. You want to get a rough approximation as to the location of the unknown material on the electrostatic series. You only have two tools at your disposal; some wax and a charge detector. Design an experiment (procedure) that will help you...
  24. D

    Relativity of position and velocity in classical mechanics

    I'm currently collating my own personal notes and would really appreciate some feedback on my description of the relativity of position and velocity in classical mechanics. Here is what I have written "Position is clearly a relative quantity as two inertial frames S and S' displaced by a...
  25. _Kenny_

    Quantum conditions for position and momentum operators

    Hello! I'm currently making my way through the book "Quantum Field Theory of Point Particles and Strings" and on page 13 they talk are talking about quantization of the classical versions momentum and position. The first part to quantizing these is turning them into operators. The books goes on...
  26. AwesomeTrains

    Maximum position expectation value for 1D harmonic oscillator

    Hey, I'm stuck halfway through the solution it seems. I could use some tips on how to continue. 1. Homework Statement I have to determine a linear combination of the states |0\rangle, |1\rangle, of a one dimensional harmonic oscillator, so that the expectation value \langle x \rangle is a...
  27. AwesomeTrains

    State transformation - Position to momentum space (Dirac)

    Hey everyone! It's my first semester with quantum mechanics and I'm uncertain if my solution of this problem is correct, would be nice if someone could check and let me know :smile: 1. Homework Statement I have to calculate the representation of the state: |\alpha \rangle \equiv exp[-i...
  28. A

    Position measurement in Non-Relativistic QM

    I've read several times in textbooks that in NR-QM you can measure with exact precision the position of a particle if you don't care at all for the momentum (because the uncertainty of the momentum will be infinite), it always seemed reasonable enough for me but now that I think about it, it...
  29. T

    How can you actually measure the electron position?

    Standard quantum mechanics text-books discusses Born rule, which states that the probability of finding a particle in a certain region in space is given by $$ |\Psi ({\bf r},t)|^2d^3r $$ Thing is, I never have seen a discussion about how you can actually measure the particle position in a...
  30. Drakkith

    Position at Which 2 Cars Pass Each Other

    Homework Statement Anna is driving from Champaign to Indianapolis on I-74. She passes the Prospect Ave. exit at noon and maintains a constant speed of 75 mph for the entire trip. Chuck is driving in the opposite direction. He passes the Brownsburg, IN exit at 12:30pm and maintains a constant...
  31. D

    Find the position of the centroid of the shaded area

    1. Find the position of the centroid of the shaded area http://imgur.com/ieiSPPY 2. The black triangle with the square cut out is where the centroid must be located.I know that the object is symmetrical and the triangle can be divided into parts with two smaller right angled triangles I have...
  32. A

    Multiplexer as a Position Sensor: How?

    Purpose: Create a position sensor using LEDs. Goal: Increase or decrease a pulse width in response to direction of movement. Chips Involved: 1) Clock. 2) 2x DM74150 (16×1 Multiplexers.) 3) 2x SN74193 (4-bit Binary Counters.) 4) 1x SN74LS112 (Negative Edge Master Slave JK Flip-Flop.) 5) 1x...
  33. H

    Force as a function of position, given x(t)

    Let me make this clear, this is not a homework question, I'm just curious. So I know a common question is finding velocity as a function of time given force as a function of position. I was curious, however, as to go backwards, starting with position as a function of time, and then finding force...
  34. S

    Position and magnitude of the maximum bending moment

    Homework Statement I need to calculate the position and magnitude of the maximum bending moment. Knows are: E=210GPa Homework EquationsThe Attempt at a Solution I've calculated the following: R1=33kN R2=32kN From the shear force diagram I know that at 2m from R1 at the concentrated load of...
  35. RileyF1

    Deriving Position WRT time of ball travelling on curve

    Homework Statement [/B] I'm trying to write a program in MATLAB which demonstrates a tautochrone curve and how the starting point of a ball is irrelevant as to the time it takes to get to the lowest point in the curve (without friction). At the moment I'm just trying to model it using a simple...
  36. Alex_Neof

    Centroid Position of a Lamina Bounded by a Curve

    Homework Statement A lamina is bounded by the x-axis, the y-axis, and the curve ##y = 4 -x^2.## Determine the centroid position ##(\bar{x},\bar{y})## of the lamina. Homework Equations ## A = \int_a^b (f(x) - g(x)) dx ## (Area) ##\bar{x} = \frac{1}{A}\int_a^b x(f(x) - g(x)) dx ## ##\bar{y}...
  37. F

    Interstitial position probability?

    Homework Statement A silicon crystal is being doped with Ni atoms. The formation energies for substitutional and interstitial Ni atoms are Es= 0.74 eV and Ei=0.16 eV, respectively. At 320 centigrade, what is the probability for a Ni atom to be placed in an interstitial configurations...
  38. D

    MHB Position vector question. Tough to solve.

  39. C

    Position vector in torque (and angular momentum)

    Torque is defined as the cross product of position vector and force, i.e. \vec \tau = \vec r \times \vec F . However the force vector \vec F is fixed, but the choice of origin is arbitrary, making \vec r also arbitrary. Does it make the torque vector also arbitrary, which apparently shouldn't...
  40. Quantioner

    The Wick rotation in position space

    The Feynman propagator is $$ G_{F}(x) = \int d^4p \, \frac{e^{-ip x}}{p^2 - m^2 + i\epsilon}. $$ I want to understand why the directions of Wick rotation in position space and momentum space are contrary. Every book I find says something like "we should keep ##xp## unchanged", but why? As we...
  41. A

    Describing a system by position and momentum.

    We often come across the statement, 'any measurable quantity of a system can be known by knowing its position and momentum'. I do not understand this. If position and momentum of a particle is given, how do we know its velocity? For that, mass also has to be specified right?
  42. D

    Kinematics: given 2 position vectors, time, and V of earlier

    If you know the position vectors of a particle at two points along its path, change in time between the two positions, and the particle's velocity at the earlier point, what quantities can you calculate? a)average acceleration b)final velocity c)average velocity d)displacement My answer was...
  43. A

    Uncertainty of position in an infinite potential well

    The ground state energy of a particle trapped in an infinite potential well of width a is given by (ħ2π2)/2ma2. So the momentum is given by (2mE)1/2 = ħπ/a. Since this is a precise value, doesn't that mean that we know momentum with 100% certainty? And if that is the case shouldn't the...
  44. goonking

    Graph of a particle's position

    Homework Statement Homework EquationsThe Attempt at a Solution the particle is oscillating so we know at 1.5 seconds, it is at the equilibrium point , where speed is highest. (the speeds are 0 at the highest and lowest points of the graph.) we see that it goes from -6m to 6m, which is 12...
  45. N

    How much does the raft move with change of position?

    heres the problem... and i figured out part a but don't understand how to get the second part, here is what i have done... my question is should the angle be from the point of origin? what I am getting is -2.12 meters in a direction of -45 degrees. is this correct? I'm using x2-x1/y2-y1 to...
  46. D

    Find the equilibrium position of the winch

    Homework Statement A whip made from a material shaped shaft axis radius R and moment of inertia I and a crank with the axis perpendicular to the axis of rotation of length l and mass m, while the rest parallel to the handle - mass ##m_{2}##. It hangs on a hoist that has mass m. Suppose rope...
  47. A

    Horizontal & vertical angle of antenna beams & UE position

    Hi this is my first post here. Sorry for this naive question xD I want to calculate antenna gain for which I need the horizontal Φ and vertical θ angle of an antenna beam. The formula for gain is. is it ok to convert the rectangular coordinates of antenna into spherical coordinates and compute...
  48. Praveen Vijayan

    Uncertainity Principle: possible to know the momentum and position?

    The principle states it is impossible to 'simultaneously' know the position and momentum(velocity)of an object. Position is something that can be noted at a particular instant, as from a photograph whereas velocity is something that can only be measured over a period of time,as from a movie. The...
  49. E

    Position Eigenstates Indeterminacy

    How large could position eigenstates indeterminacy be so as to be indistinguishable from classical state? For example. If a particle is smeared by 10 Planck length.. could we tell or could we consider it as classical state? What is the most accurate device that has probe the smallest region...
  50. S

    Confused by different definitions of position

    Hello, I am self-studying an introductory mechanics textbook and while I feel I understand the material there pretty well, I came across across an online definition of position which seems at odds with the explanations and definitions in my book. The definition that confused me is: ""Position...
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