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.
At the beginning of every course in QFT we are told that, unlike in ordinary QM in which the position variable is a physical observable , the position variable in QFT is just a label.
Yet there are areas within QFT where the position variable is treated like a real physical degree of freedom...
In QM a free micro particle with definite momentum has not definite positions.But why does in classical physics a free particle with definite momentum still have definite positions but not blurred as in QM?(Because we can deduce Classical Physics from QM)
This is a homework question from my friend, I found the time but a tough differential equation occurred when I was trying to find accelaration, is there a simple solution for this?
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?
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?
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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##...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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.
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...
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...
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?
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##...
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...
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.
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...