0
votes
1answer
5 views

Second Qubit Not Flipped in Hadamard Gate

I'm very new to QM and Quantum Computing and I have a likely simple question, It may simply stem from my lack of knowledge of vector calculus. We have a 2-qubit quantum state: $$ \mid\psi\rangle = ...
4
votes
0answers
20 views

Gauge choice after Spontaneous Symmetry Breaking

After the spontaneous breakdown of local symmetry in presence of gauge fields (Higgs Mechanism), we can always choose a gauge where the Goldstone bosons are eaten up by the gauge field. Which ...
0
votes
2answers
20 views

Extract particular ions from an ionized gas

Is it possible to extract any particular ion ( either positive or negative ) from ionized gas ( or plasma ) without spending any ...
6
votes
2answers
38 views

Center of mass frame for massless particles

Given a scattering event where a photon and electron go in and a photon and electron come out, what is the center of mass frame? I'd say, since the photon has no mass, it's the rest frame of the ...
-1
votes
0answers
5 views

Space elevator: a Earth rotation brake model

I read this article regarding the space elevator. A very long carbon nanotubes string, running from the Earth surface into the vacuum of the space. Tension and friction, an enormous quantity of ...
4
votes
6answers
73 views

What is the relationship between force and momentum in collisions?

I know that $ \Sigma F = \Delta mv/\Delta t$. But if we had a marble that moves in a straight line at a constant velocity and colloids with another marble. Because of the law of conservation of ...
1
vote
1answer
122 views

Question about buoyancy

I took an empty clear sphere with radius r, put some weight inside this sphere, and put in into the water. I calculate the buoyancy force as: Volume of the sphere = Volume of the water displaced ...
10
votes
4answers
417 views

What's wrong with this application of Thomas Precession to circular motion velocity measurements?

If you happen to have the Third Edition of Classical Electrodynamics by John David Jackson, turn to section 11.8, as that's where I'm getting all this from. If not, you should still be able to follow ...
-2
votes
2answers
30 views

Flea jumping question [on hold]

During takeoff, a flea develops an acceleration of $3m/s^2$. It reaches a max height of 36mm. How long does this acceleration last? Finding the initial velocity was fairly easy, but finding the time ...
2
votes
1answer
50 views

finding equation of a water droplet

I have a water droplet which is falling down through its gravity. I've supposed that my droplet is an ellipsoid and I want to find the equation that represents this ellipsoid in XYZ coordinate system. ...
4
votes
4answers
251 views
+50

Why does a conservative force return the work done against it by a body to that body?

Newton's 3rd law of motion: Newton's third law of motion or the law of action and reaction implies that there is no isolated force in nature. Whenever there is any force at all , there must be ...
0
votes
0answers
6 views

How to drive quadrotor moments of inertia

I would like to know how moments of inertia (i.e. around x,y and z axes) of a quadrotor is driven given the total mass and the distance from the origin of the quadrotor to the center of a $i$th ...
1
vote
1answer
23 views

Speed with wind resistance

This is probably a basic question, but it has been a while since I did anything like this. If a boat is sailing forward at speed $x$ and the direction of the wind, with magnitude $y$, is either equal, ...
1
vote
2answers
30 views

what make the bottom portion of a wheel in rolling motion move?

As I just learn about the rolling motion which is the combination of pure translation and pure rotation. The top portion of the rolling body has the speed of double speed at the center of the object ...
29
votes
7answers
3k views

Homemade salad dressing separates into layers after it sits for a while. Why doesn't this violate the 2nd law of thermodynamics?

The oil, vinegar and other liquids in homemade salad dressing separate into layers after sitting for a while, making the mixture become more organized as time evolves. Why doesn't this violate the ...
0
votes
0answers
12 views

A box up an inclined ramp with a coefficient of friction [on hold]

A 6.25 horsepower motor to pull the boxes a distance of 8.35 meters up a ramp inclined at an angle of 36.2º with respect to horizontal. The boxes have a coefficient of kinetic friction of 0.381 as ...
0
votes
0answers
16 views

Projectile Aiming [on hold]

I'm having a but of trouble with a game I'm programming. What I have is an enemy who periodically shoots a laser at the player if they're close enough. I've been trying to come up with a way to make ...
0
votes
0answers
22 views

Normalize human motion

I'm working on human motion recognition. I have question about normalization. Based on the literature, there are many methods used for normalization. I don't understand how there do normalization, ...
1
vote
1answer
24 views

Is a double integral required to find the moment of Inertia of a non-uniform sphere?

A sphere of radius $0.17m$ has a density $\rho$ described by the equation $\rho = 3500 kg / m^3 - (9500 kg / m^4) r$, where $r$ is the distance from the center of the sphere. What is the moment of ...
0
votes
2answers
58 views

If Earth starts moving when attracted by an object, where does the energy come from?

Suppose a body(very big but not bigger than Earth) moves against gravitational force of Earth. The force will do negative work on the body decreasing its kinetic energy. The decreasing energy is ...
1
vote
1answer
60 views

How to find the electric field of a charged tube?

Let's say there is a charged tube(cylinder with no top or bottom) with radius $a$, length $l$ and charge $q$ and a point which is collinear with the centre of the charged tube. Anyway, since we can ...
1
vote
1answer
29 views

Pressure and variation in pressure due to depth

In my class, we were shown the following problem: Using the equation $P_1$ = $P_0$ + $\displaystyle\rho$gh, where $P_1$ is the pressure at Superman's mouth and $P_0$ is the pressure at the surface ...
1
vote
3answers
22 views

Sound diffraction through a single slit

When sound waves diffract through a single slit, do they produce an interference pattern which is mathematically identical to that of light waves in the corresponding experiment?
1
vote
0answers
18 views

Extra-Solar System Global Warming?

The sun probably easily dominates in its impact on the atmospheric temperature of Earth. However, for roughly half of each day, each side of Earth faces away from the sun. Combined, the time spent ...
1
vote
1answer
112 views

Calculating Phase Diagrams (Calphad)

I am calculating the phase diagrams for Li-Mg binary alloy with reference to the following text: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=5600701 In the equation used in the above ...
0
votes
0answers
6 views

What is the force of the wind resistance? [on hold]

A sled of mass 15.0 kg is pulled forward with a force of 35 N. Also a frictional force of 12.2 N acts on the sled. Finally a wind resistance acts on the sled. Over a period of 18.0 s the sled ...
2
votes
1answer
50 views
+100

Wavefunction of isomers

In quantum chemistry, the wavefunction for a molecule can be viewed as the output of a function $\xi(m, n_1,..., n_k)$ with $m, n_i \in \mathbb{Z}^+$ that returns a $|\psi\rangle$ that satisfies a ...
1
vote
1answer
36 views

Hooks Law and acceleration [on hold]

A 435 gram sharpened piece of iron rebar into a spring loaded device. It takes a force of 355 Newtons to compress the spring by 27.5 cm. With what speed does the rebar shoot out of the device? ...
3
votes
0answers
22 views

Two carts connected by spring on frictionless track

I have the following homework problem: Consider two carts of equal mass m on a horizontal, frictionless track. The carts ar5e connected by a single spring of force constant k, but are otherwise ...
0
votes
2answers
62 views

Is centrifugal force equal in magnitude to the centripetal force in the frame of a body undergoing circular motion?

I was working out the minimum tangential velocity required for a swing to complete a full revolution and assumed the centripetal force is equal to the centrifugal force, so that I could set the weight ...
0
votes
1answer
4 views

Determining flexural modulus by performing 3 point bending test using hollow cylindrical tube

I would like to decide the flexural modulus of the material of plastic tube by performing 3 point bending test according to the ASTM D 790 procedure. In ASTM D 790, the form of the specimen is ...
0
votes
1answer
20 views

Two Limits in Thermodynamics - Reducing Driving Force and Increasing Resistance

I just wanted to clarify what is probably a very obvious idea. Suppose I'm holding a a piston separating two containers at different pressures. If I release the piston, it will naturally move, ...
5
votes
4answers
121 views

Is there some special case where a fermion can mediate a force?

Looking at the comments of this questions Does the gravitino contribute to the gravitational interaction? and even considering that the answers here in this other question Why are all force particles ...
1
vote
1answer
18 views

Say, a liquid is made to flow in a tube. Why does the layers of the liquid in contact with walls of the pipe have zero velocity?

Say, a liquid like water is made to flow in a pipe. Why does the layer of water near the walls of the pipe have zero velocity? Does that mean that the layer of water near the pipe is stationary and ...
0
votes
0answers
10 views

Role of the crystallographic point group on properties of tensorial elasticity

If a space point group for a crystal is known, does this automatically define the elastic tensor symmetry of the material? What further implications can be found? The crystallographic subgroups: ...
1
vote
3answers
29 views

Mathematical Reasoning for Fluid Pressure as a Scalar

This question from a while ago and answers/comments to this question from earlier today both make heavy mention of the fact that fluid pressure is a scalar. Although this information was surprising ...
-2
votes
1answer
24 views

What causes the recessed blade of some folding knives to emerge in a kinetic opening?

KINETIC OPENING OF FOLDING KNIFE (FK) Several legal jurisdictions around the World, including Australia, have assented legislation/regulation which attribute the emergence of the recessed blade in the ...
0
votes
2answers
522 views

How do I express the interaction energy between two charged spheres?

Consider two identical insulating spheres each with radius $R$ and uniform charge $Q$ through their volume. They are separated from their centers by a distance of $d>2R$. Here is my general ...
2
votes
3answers
212 views

Reverse bias P-N junction

I am not able to understand why the PN junction does not conduct when reverse biased. Can't electrons travel from the N side through the power supply to the P side where they can jump from one hole to ...
1
vote
2answers
115 views

How can Lorentz contraction be “directly” measured?

If one is watching a relativistic object of e.g. spherical shape, which emits enough light to be detectable, it will, despite being Lorentz contracted, appear of its natural shape, although rotated. ...
0
votes
2answers
209 views

Measurement of the energy of an atom using a cold substance

An atom was prepared in a superposition of ground state and excited states.I propose to measure the state by coupling the system to a cold enough substance. By cold enough I mean $$kT\ll E_1,$$ where ...
0
votes
0answers
26 views

At what velocity does space no longer equal a vacuum? [on hold]

In Dr. Alistair Reynolds's book (Revelation Space), he mentions that space only equals a vacuum at low speeds. At which velocities would space no longer count as an almost vacuum?
6
votes
1answer
67 views

Why is the Oort cloud spherical?

Having read up a bit about the Oort cloud hypothesis, I find I don't quite understand this. Why is the Oort cloud spherical while the rest of the solar system is disk-shaped?
-2
votes
0answers
15 views

Leptons slide between quarks? [on hold]

I wonder if one of particles (maybe quarks?) are constructors of highways in 3d field for others floating around re/distributing energy by some (leptons?), restricted to laws set by (bosons?). If ...
0
votes
0answers
33 views

No length contraction!

Suppose a person standing on a platform were to observe and measure the length of a train passing by. Instead of the usual approach involving a clock and knowing the speed of the train, the person ...
5
votes
1answer
125 views

Why is cooling much harder than heating?

I'm trying to invent a distillation apparatus that runs solely on electricity. Suddenly, I realized that cooling things is really hard, while heating them up is so easy. Actually, it seems that there ...
0
votes
1answer
43 views

Do we exist in multiple dimensions?

I have heard that there are 12 spacial dimensions. Does this mean that this many are possible,or that 12 dimensions actually exist? If the ladder, then do the same things that exist in 3 dimensions ...
2
votes
2answers
391 views

Does coffee cool faster than tap water?

A friend of mine, based on casual observation, believes that coffee will cool faster than ordinary hot tap water. Being curious about this I have tried to investigate it myself, but I'm not well ...
1
vote
3answers
81 views

Variational Theorem proof

I have been trying to prove variational theorem in quantum mechanics for a couple of days but I can't understand the logic behind certain steps. Here is what I have so far: \begin{equation} ...
11
votes
4answers
4k views

Why don't planets have Circular orbits?

This might be a completely wrong question, but this is bothering me since many days ago. Given the mass (Sun) curves the space around it, gravitation is the result of such curved space (Correct me if ...

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