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. Like Tony Stark

    Measuring position, velocity and acceleration in relative motion

    Well, ##r(t)## in ##A## is just a vector ##(0;y)## because is tangent to the trajectory. Then, from the perspective of ##B## the particle moves in an uniform circular motion. Is this right? The velocity from ##B## must be ##\omega##, right? And what about acceleration?
  2. crownedhues

    Position in Velocity-Time Graphs

    Would it be correct if I multiplied the time by the velocity of the object since the units would cancel into meters? So for example, I multiply 2 seconds by 1m/s which gives me 2m - would that be the object's position?
  3. adosar

    I Position of Particle in Special Relativity (A vs B)

    Recently I have come into Special Relativity and specifically Lorentz transformation. Let's assume two frames A and B moving relative with speed ##v##. The position of a particle moving with respect to B is given by ##x′=f(t′)=3t′##. What is the function of position ##x=f(t)## of the particle...
  4. E

    Question about equilibrium position

    Suppose we have a reversible reaction $$aA + bB <=> cC + dD$$ which is exothermic in the forward direction. If the temperature of the system decreases, the rate of the forward reaction will increase so that the quotient Q increases to the new (higher) value of Kc. This I think I am ok with (I am...
  5. S

    Tension and speed of bowling ball pendulum passing the equilibrium position

    For part a I used conservation of energy. -m*g*cos(θ)*L+1/2*m*0^2=-m*g*L +1/2*m*v^2 => v = sqrt(2*g*L(1-cos(θ )). b) For b I was think that T = mg in the equilibrium point but that doesn't invole θ in the answer. So that's why I tought that T*cos(θ ) = mg. So that the tension is mg/cos(θ). But...
  6. H

    I Wave function when there is coupling between spin and position

    Why can't the general state, in the presence of coupling, take the form $$\psi_-(r)\chi_++\psi_+(r)\chi_-$$ where ##\psi_+(r)## and ##\psi_-(r)## are respectively the symmetric and anti-symmetric part of the wave function, and ##\chi_+## and ##\chi_-## are respectively the spinors representing...
  7. Arman777

    I Fınding the position of a point on the line

    Let us suppose we have a line ##l_1 = ax + by + c = 0## and we have a point P, ##P(x_p, y_p)## that is outside of this line. If we draw a perpendicular line from point ##P## to a point on the ##l_1##. What would be the coordinates of this point ? I know there are many ways to do it. But I am...
  8. GuillemVS

    How to get the absolute position of a relative object?

    I don't know if this question suits this forum, I post this here actually because I saw (if not my memory is failing) that here it is also possible to solve math problems. So, back on track: I like to discover things from myself, so I searched for the Euler's formula, willing to find the...
  9. kolleamm

    I Rotate a shape back to its original position with the fewest rotations

    Summary: Rotate a shape back to it's original position with the least amount of rotations. Lets say you have a cube. It's starting rotation is (0,0,0). It can be rotated on each axis ( x,y,z ) no more than once each by 90 or -90 degrees (rotation can also be skipped for any axis). The shape...
  10. karush

    MHB 2.62 Calculate the objects position and acceleration (using tikx for graph)

    2.62 An object's velocity is measured to be $v(t)=\alpha-\beta t^2$ where $\alpha=4.00\, m/s$ and $\beta=2.00 \, m/s^3$ At $t=0$ the object is an $x=0$. (a) Calculate the objects position and acceleration as functions of time (b) What is the object's maximum positive displacement from the...
  11. Benjamin_harsh

    Centre of gravity shifted to what position?

    A square sheet of metal has a square of one quarter of the original area cut from one corner as shown in the figure. Which of the following statements is true about the position of the centre of gravity of the remaining portion of the sheet? a) center of gravity lies at a distance of 5/12 of...
  12. C

    Position to momentum space in three dimensions

    Hi! I am trying to change the hydrogen ground state wave funcion from position to momentum space, so i solved the integral Ψ(p)=(2πħ)^(-3/2) (πa^3)^(-1/2)∫∫∫e^(prcosθ/ħ) e^(-r/a) senθ r^2 dΦdθdr and got 4πħ(2πħ)^(-3/2) p^(-1) (πa^3)^(-1/2) I am [(ip/ħ-1/a)^(-2)], which according to the...
  13. WrathofAtlantis

    Could wing height position (through changing pitch) affect propeller airflow?

    I am talking about low wing single engine WWII fighter types. In particular, I am interested in accelerated propeller airflow through the transition/curvature of the prop slipstream spiral distribution around the wing, from being partly below, towards mainly above the wing. This as the wing's...
  14. B

    Closed form of the position of a bouncing ball

    I know that the height before the first bounce will be ##y = g * t * t + v_0 * t + y_0##. After the first bounce, I can find y by pretending the ball was thrown from the ground with velocity ##e * -v_f## with ##v_f## being the velocity of the ball when hitting the ground, but I have to reset the...
  15. A

    Trying to calculate the time derivative of a position differential

    here I am trying to find ##\frac{d}{dt}dx## where ##x(t)## is the position vector Now ##\frac{d}{dt}(v_x(x,y,z,t)dt)=\frac{dv_x}{dt}dt=\frac{\partial v_x}{\partial t}dt+\frac{\partial v_x}{\partial x}dx+\frac{\partial v_x}{\partial y}dy+\frac{\partial v_x}{\partial z}dz## Now dividing by ##dx##...
  16. A

    A Do QED effects make a huge change to the position of the electrons?

    In https://en.wikipedia.org/wiki/Lamb_shift about the lamb shift, it's mentioned that the change in the electron's frequency due to QED effects (vacuum polarization and self-energy correction) is about 1 GHz, which would translate to an energy change of hf = 6.63E-25 J. This is 3E-7 times of the...
  17. A

    I Does the Compton wavelength put a limitation on position measurements?

    I have read on Wikipedia (https://en.wikipedia.org/wiki/Compton_wavelength) that we cannot measure the position of a particle more precise than half of its Compton wavelength, since the photon we would need will be so energetic to produce electron-positron pairs. How does the creation of...
  18. M

    Michelson-Morley Experiment: the importance of the laser position

    Why was it important that both arms were parallel and perpendicular to the rotation of the earth?
  19. D

    A position of stable equilibrium, and the period of small oscillations

    I tried by taking the derivative of the potential to find the critic points and the I took the second derivative to find which of those points are minimum points. I found that the point is ##x=- a##. I don't understand how to calculate the period, since I haven't seen anything about the harmonic...
  20. zehkari

    Find the position of a proton in an E and B field

    Hello all, I have a question with the helix path of proton in a magnetic field that I am a bit stuck on. Question: Equations: F = qv X B F = mv^2/r d=vt My Attempt: Think the graph drawn is good enough for questions (a). However, I am stuck on (b) and (c). Firstly I am not entirely sure...
  21. Haorong Wu

    The position and momentum operators for a free particle in Heisenberg picture

    Homework Statement From Griffiths GM 3rd p.266 Consider a free particle of mass ##m##. Show that the position and momentum operators in the Heisenberg picture are given by$$ {\hat x}_H \left( t \right) ={\hat x}_H \left( 0 \right) + \frac { {\hat p}_H \left( 0 \right) t} m $$ $$ {\hat p}_H...
  22. S

    Determining position of an object after inelastic collision

    Homework Statement A 39,000 lb truck A and a 3968 lb sports car B collide at an intersection. At the moment of the collision, the truck and the sports car are traveling with speeds vA = 70 mph and vB = 30 mph. Assume that the entire intersection forms a horizontal surface. Letting the line of...
  23. J

    Finding the expected value of position in a Potential Well

    Homework Statement Hello today I am solving a problem where an electron is trapped in a potential well. I have a solved Schrodinger's Equation. I am having problems in figuring out what the wave function should be. When I solved the equation I got a complex exponential. I know I cannot use the...
  24. J

    Finding the POSITION of the center of mass

    Homework Statement Three spheres are placed around a coordinate grid: one of mass m at the bottom-left, one of mass 3m a distance of 3L above the first, and one of mass 2m a distance of 4L to the right of the first. 4 points between these three spheres are labeled: A near (1.3L, 1.5L), B...
  25. J

    Describe the position of a pulley attached to a sling

    Hi, I am studying the behaviour of a pulley that is attached to a sling. The situation looks like this: There is a drum that can give or take cable. Then there is a floating pulley with a cable through it. The pulley can move on the circle with a radius the same as the length of the sling...
  26. F

    How Is the Position Function H(t) for a Yo-Yo Derived in Calculus?

    H(t) = t^3-6t^2+5t+30 this is a yo yo 30 inches above ground at t =0, at 4 secs it is 18 inches above ground. Please tell me how these figures are derived; t^3,6t^2, 5t; I realize the 30 is initial position. I am 81 but very curious. Thank you.
  27. manojr

    I Uncertainty of momentum and position

    I was reading a book which had some comments on EPR paper (Einstein, Podolsky, Rosen - 1935) like following: In Newton's physics, when two identical billiard balls hit each other head-on, bouncing off in opposite direction, knowing one ball's position and speed will also indicate other ball's...
  28. D

    Trajectory of a particle when its position vector changes

    Homework Statement The position vector of a particle changes: Only by its module. Only by its direction. What can be said about the trayectory of the movement of the particle? Obtain the answer analitically. Homework Equations None. The Attempt at a Solution I think that the trayectory...
  29. K

    Position formula in a non-inertial frame

    The equation ##x = x_0 + vt + at^2/2## is derived assuming a constant acceleration ##a##. My question is , from what frame is this path ##x(t)## described? Can I use it from a non inertial frame?
  30. gmastrogiovanni

    I Do I need energy to measure position without uncertainty?

    I state the following study and then expose my doubt at the end. MY SYSTEM A free particle (absence of forces) on one-dimensional space (X axis). INITIAL STATE At t=0 the wave function is a Gaussian wave packet NOT normalizet centered in ##x_{0}## and with standard deviation ##\sigma##...
  31. X

    I How to find the position of a celestial object in the sky?

    Hi all, I am an electrical engineering student currently involved in a project aimed to create a simple GoTo azimuth mount. I don't have a lot of background in astronomy, so I am a bit confused on how to find the position of a star in the sky. After some research on my own, I figured out that...
  32. D

    If a particle was at position X for zero time, was it there?

    A moving particle has been at position X for zero time. Was it ever at position X? Can zero time be considered as never, as in "I was in Rome for zero amount of time."? It seems like it would have been at position X if time passed in pieces the size of Plank time.
  33. Zack K

    Location of charged particle given magnitude of position

    Homework Statement A charged particle has an electric field at ##\langle -0.13, 0.14, 0 \rangle## m is ##\langle 6.48\times10^3, -8.64\times10^3, 0 \rangle## N/C. The charged particle is -3nC. Where is the particle located? Homework Equations ##\vec E=\frac 1 {4π\varepsilon_0} \frac q {|\vec...
  34. R

    Other Transitioning from PhD to a different type of research position

    I'm currently in the process of applying for research positions in my field, unfortunately it's somewhat niche and research positions rarely become available. When they do they tend to go to those who they know already. So, I'm having to look at different research fields, which is kind of...
  35. E

    Other Advice for Writing a Research Plan for a Postdoc Position

    Hi! I would like to apply to a postdoc position, but one of the requirements is to detail at least a 2-page research plan on a certain topic. I haven't worked on that topic specifically before, so, I would need to research it. However, this may take sometime to know exactly what to do, and I...
  36. Talisman

    I Mirrors, phase shifts, and position

    I'm confused about something regarding phase shifts but I'm not sure I've pinned down what. I had always thought of a mirror as introducing a global phase shift of π in the position basis, but I only now realize that this makes no sense: of course -A ⊗ B = A ⊗ -B, so a global phase shift is not...
  37. Cathr

    Question about a derivation: velocity and position

    I started studying Lagrangian mechanics, and the movement equation is like this: d/dt (d/dz') L - d/dz L = 0 if the movement is on the z axis. Now the problem is, let's say L = M(z')2/2 - Mgz. How do we derivate an expression depending of z with respect to z' and also , an expression depending...
  38. TachyonLord

    The order of calculating velocity and position alters the solution?

    So I tried solving the differential equation for a spring - mass system using Euler's Algorithm in Python. The equation being d2x/dt2= -4π2x (The equation was obtained by Dimensional Analysis) here x and t are both dimensionless equivalents of position...
  39. Dorian

    Position vs Time Graph: Simple Harmonic Motion

    Homework Statement [see attached photo] I seek specific help with (a) only. The answers to this question are provided in the back of the textbook, so I know the answers (I hope). Homework Equations ##x(t)=Acos(\omega t+\phi _{0}),## ##v_{x}(t)=-A\omega sin(\omega t+\phi...
  40. N

    Solving Baseballs Colliding with a Car: Find Speed & Position

    Homework Statement You throw baseballs at a mass rate of σ kg/s (assume a continuous rate) with speed u at the back of a car. They collide elastically with the car. The car starts at rest and has mass M. It moves on the ground with no friction. Find its speed and position as a function of time...
  41. TytoAlba95

    Silent mutation and third position

    I got this question in an exam. Why do silent mutations always affect the third position of a codon? I have no clue about it.
  42. P

    How does the position of a force affect a spinning wheel

    Homework Statement 1m diameter solid disc spinning at 10 rpms with a subsequent .5m diameter solid disc being driven by the 1m sokid disc. Homework Equations Not sure there is one for my particular situation. The Attempt at a Solution Just using the torque is equal to force times distance...
  43. J

    Position wave function of energy eigenstates in 1D box

    Homework Statement Consider a particle which is confined in a one-dimensional box of size L, so that the position space wave function ψ(x) has to vanish at x = 0 and x = L. The energy operator is H = p2/2m + V (x), where the potential is V (x) = 0 for 0 < x < L, and V (x) = ∞ otherwise. Find...
  44. J

    Position of particle in inertial reference frame

    Homework Statement The position of a participle in a fixed inertial frame of reference is given by the vector r = i(x0 + Rcos(Ωt)) +j(Rsin(Ωt))where x0, R and Ω are constants. a) Show that the particle moves in a circle with constant speed Homework Equations F = mv2/r The Attempt at a...
  45. E

    Kinematics: find the particle's position as a function of time

    Homework Statement There is a particle that moves in 1-dimension. mass is m, force on the object is given as a function of position(x), Fx= -mω2x.(ω is constant) when t=0 particle has x0>0, and velocity is zero. find the particle's position as a function of time. Homework Equations There is a...
  46. PrinceWalnut

    Physics How to recommend a research mentor for a faculty position?

    Hi all! I'm an undergrad in physics in the USA, and a research professor I've been working with for the past ~2 years is applying for an open faculty position at an Australian university. She hasn't asked me to recommend her in any way, and I know that in all likelihood the word of some...
  47. opus

    When is the velocity zero or changing?

    Homework Statement Use the graph (attached below) to determine the time intervals when the velocity is positive, negative, or zero. Homework EquationsThe Attempt at a Solution The graph is of a position function. Velocity is the derivative of position. Velocity will be zero when the derivative...
  48. K

    A Is There a Solution for a Particle Falling into a Gravitational Well?

    Hello, I am trying to find a function x(t) that describes a particle falling into a gravitational well from a certain distance. So, for example, I am trying to figure out the differential equation: F = m*(dx^2/dt^2) = -GMm/x^2. Or simply, dx^2/dt^2=-GM/x^2 or even more simply, x''(t)=-k/x^2...
  49. Al_Pa_Cone

    Determine the position and magnitude of the max bending moment

    Homework Statement For my question, I am following a previous method I used in my HNC where I had to determine the position and magnitude of the maximum bending moment. I am now working on my project and I have revisited this question but I am having some issues in my method. The above diagram...
  50. Matt Chu

    Time Derivative of Expectation Value of Position

    Homework Statement I want to prove that ##\frac{\partial \langle x \rangle}{\partial t} = \frac{\langle p_x \rangle}{m}##. Homework Equations $$i\hbar \frac{\partial \Psi}{\partial t} = -\frac{\hbar^2}{2m} \frac{\partial^2 \Psi}{\partial x^2} + V \Psi$$ The Attempt at a Solution [/B] So...
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