2
votes
1answer
125 views

Can someone please explain impedance matching and wave reflection?

I'm reading Wikipedia's article on impedance matching (http://en.wikipedia.org/wiki/Reflections_of_signals_on_conducting_lines) and this just seems so foreign to me. 1) What does it mean for a ...
3
votes
1answer
1k views

Calculating time to reach certain velocity with drag force

I was given a problem for homework where we needed to calculate the time for a falling object to reach a certain velocity when accounting for drag force. I did it by setting up acceleration as a ...
31
votes
5answers
3k views

How is it possible to accelerate a neutron?

It is possible to accelerate a charged particle in an electric field, how is it possible to accelerate a neutron? How can we control its velocity?
1
vote
0answers
26 views

Matter and Electrical Impulses

The human brain is composed of about 100 billion neurons; with trillions of synapses. These synapses transmit signals, which is obviously made of some sort of matter. This is what creates thought and ...
0
votes
1answer
45 views

Gravitiation force of a sphere

Was wondering about Shell Theorem, specifically about the immediate results. Force (on a point mass) inside a shell is 0. Force (on a point mass) outside a shell is GmM/r^2 From what i know the ...
1
vote
1answer
148 views

Drag - Dimensional Analysis / Buckingham Pi

Dimensional Analysis / Buckingham Pi Theorem I'm working on dimensional analysis and I'm having trouble. Here's a problem from my book I'm working on for practice. I'm suppose to consider a small ...
0
votes
0answers
153 views

3DAnisotropic oscillator in Spherical Harmonic basis-States with $L_z=0$

I've been trying to prove a rather simple looking concept. I have a code that calculates states of a 3D anisotropic oscillator in spherical coordinates. The spherical harmonics basis used to expand ...
2
votes
1answer
47 views

How to separate different CP eigenstates?

Someone can tell me how to separate different CP eigenstates(even and odd) using angular distribution of B meson decay?
6
votes
1answer
91 views

Quantum ring and Dirac Quanitzation

I had a small question. If you look at the energy eigenvalue problem for a particle restricted to a ring, you get $$E_n = \frac{\hbar^2n^2}{2mR^2}.$$ If you then put a solenoid inside the ring, then ...
1
vote
2answers
300 views

How does the temperature in a bucket of water with ice change over time?

I'm curious what happens to the temperature of the water in a bucket of water with ice in it. Let's start with a bucket with just ice in it, and we add water, in a room which is room temperature. It ...
1
vote
0answers
136 views

Relationship between thickness and resistivity of thin metal films, finding the characteristic thickness and the cut off resistivity

I’m working on a lab report on the relationship between thickness and resistivity of thin metal films. I collected data that was approximated to the 2nd order exponential decay equation: $$7\times ...
2
votes
2answers
139 views

Differentiating the Hamiltonian Operator, $\hat{H}$

Firstly let $\hat{H}$ denote the full energy of the electromagnetic wave. I'm trying to differentiate the Hamiltonian operator with respect to the components of momentum, i.e. $$\frac{d}{dp_x} ...
1
vote
1answer
108 views

How many wavefunctions are in a minimal basis set for benzene?

I am reading Modern Quantum Chemistry by Szabo and Ostlund and on page 62 he says "A minimal basis set for benzene consists of 72 spin orbitals." I tried to understand this number but failed. ...
1
vote
0answers
47 views

Does a pulled rubber band contain as much energy as a twisted rubber band?

lets say I take two similar rubber bands. One of them I pull until it almost reaches its breaking point. The other I twist until it almost reached its breaking point. Do both of these rubber bands ...
0
votes
0answers
82 views

Is there a way to measure the energy stored in a twisted rubber band?

I am building an energy storage device using rubber bands. It contains 24 bands which are twisted by a set of gears. I would like to measure (or predict) the amount of energy that the device can ...
2
votes
2answers
81 views

How to meaningfully describe the practical effectiveness of one large bomb versus a series of many small bombs, all else constant? [closed]

Background: Given two sets of conventional bombs (constituted of fuel which explodes by way of chemical decomposition reaction) : Set 1 - One shell of a given volume encasing a given amount of fuel. ...
5
votes
1answer
188 views

Can quantum vacuum carry entropy?

So, we know that the state of quantum vacuum does carry energy, as it was measured in the Casimir effect. This energy comes from particles almost instantaneous creation and annihilation. Even if they ...
1
vote
1answer
232 views

Permeability and magnetization of soft iron at various fields

I'm curious as to the magnetic permeability of soft iron (and other materials if available) under different fields. I know permeability of materials changes with field (that is why we have saturation ...
2
votes
0answers
704 views

Effective refractive index calculation of fiber core

Can someone pls explain what is effective refractive index of fiber core and how to calculate it theoretically? Suppose the fiber core refractive index=1.4446 and cladding refractive index is= ...
1
vote
1answer
228 views

Do different density objects in liquids affect net weight [duplicate]

I would test this but I have no tools to test it with. If I have a beaker of water and weigh it on a measure. Then I stick my fingers in the water (it doesn't over flow) does the weight change or ...
2
votes
1answer
94 views

Can these two terms cancel out?

In trying to prove that $$\Gamma_{\mu\nu\lambda} = \eta_{ab}J^a_bJ^b_{\nu\lambda}.$$ The author canceled out while expanding the first equation $$J^a_{\mu\lambda}J^b_\nu$$ with ...
0
votes
0answers
68 views

Equivalence of derivation of Majorana fermions

Perhaps is this a stupid question but I have really no answer. To prove the emergence of Majorana bound states I search zero-energy solution of the Bogoliubov - de Gennes equation $$ ...
1
vote
0answers
58 views

Why are atoms with a complete octet the most stable ones? [duplicate]

I mean are the valence electrons in an octet arranged so that they have the lesser amount of energy that is lesser than electrons in other atoms?
2
votes
1answer
193 views

How fast would a bullet travel through liquid air?

According to Wikipedia, a bullet from a .22 Long Rifle travels at a speed of 320 m/s and the density of liquid air is 870 kg/m3. What equation would calculate the speed of a bullet fired into liquid ...
1
vote
1answer
209 views

How torque and friction cause wheel to roll

I apologize if this question has been answered before, but I did not find the explanation that I needed. If a torque is applied to a wheel situated on a frictional surface, what forces cause the ...
3
votes
1answer
216 views

What is the simplest way to perform a Cavendish experiment?

The Cavendish experiment is cool, but seems complicated to experimentally perform. What is a simple way to recreate the experiment?
1
vote
2answers
249 views

Differentiation in general relativity

If we have: $$ \frac{d\phi^a}{d\tau}= \frac{\partial \phi^a}{\partial x^\mu} \frac{dx^\mu}{d\tau} \tag{1}$$ Differentiating it, we get: $$ \frac{\partial \phi^a}{\partial ...
0
votes
0answers
12 views

Which constant is required to calculate the energy in a thermal analysis?

I want to calculate the energy in a thermal analysis. I want to do it in analogy to the electrostatic field, because I'm interested calculating the $H_1$ error in a Finite Element analysis. For ...
1
vote
0answers
48 views

diamagnetism in constant magnetic field

"The diamagnetic materials repel the materials which produces magnetic field, so putting these materials in the proximity of the magnetic field generating materials produces the effect of the ...
1
vote
0answers
26 views

How to calculate resources taken up in quantum computation

Suppose I have $n$ qubits namely $\{|\psi_{1}\rangle,|\psi_{2}\rangle.....|\psi_{n}\rangle\}$. I apply a series of unitary operations $U_{1},U_{2}...U_{n}$ (applied in order) to these qubits. Each ...
1
vote
1answer
156 views

How to calculate the photoelectric effect with photon efficiency?

I am not sure exactly where to go with this problem. The problem states: "A $1.3 \, \mathrm{mW}$ laser ($\lambda = 545 \, \mathrm{nm}$) shines on a cesium photocathode ($\phi = 1.95 \, \mathrm{eV}$). ...
3
votes
0answers
71 views

Perpetual Mobile and Gravitation

I have fundamental question about what is called the “law of conservation of energy”. We all hear about the tidal power stations which using the tidal power. The source of the tidal power came from ...
1
vote
1answer
122 views

Loading a capacitor in an RC circuit

I have an RC circuit to which I am going to apply voltages of 5V every 100ns. So every 100ns, the capacitor will change its "state" from charging up to uncharging. I have been trying to find the a ...
1
vote
0answers
50 views

Looking for binning software [closed]

I'm looking for a software which should do the following Take a set of data $X$ and $Y$: Procedure A Finds the max and min in $X$ Divide this interval in a number of bins chosen by me For each bin ...
0
votes
1answer
31 views

Finding the distance between two osclilating particles in a wave

Assume a wave function $\psi = \psi(x,t)$ where $x$ is position from the starting point $(0,0)$ and $t$ is time. Two oscillating points A and B are located at $x_1$ and $x_2$ respectively with $x_2 ...
0
votes
0answers
33 views

Heavyside Lorentz units and Gaussian units

What is the relation between Heavyside Lorentz units and Gaussian units? From this Wikipedia article, I noticed there are $4\pi$ difference between them, but my TA wants more. Is there other ...
0
votes
0answers
46 views

Difference between non-adiabatic coupling and diagonal Born Oppenheimer correction?

I think my question is quite well formulated in the title! I'm trying to understand collision process involving crossing between different electronic states in the potential energy surface, which ...
3
votes
2answers
247 views

Is there a mathematical equivalence between gravitational optics and quantum optics or are they mathematically incompatible theories?

I know that massive gravitational bodies will curve the path that light travels. I think that quantum optical mediums also bend light. I am still confused of whether quantum optical mediums actually ...
1
vote
1answer
166 views

How does underwater sound sound?

I have been thinking about underwater sounds (i.e. sounds produced and recorded underwater), what exactly the water does, and how to emulate this effect. Imagine a sound played underwater (e.g. from ...
3
votes
1answer
188 views

what physical quantity do real scalar field operators create/destroy?

Let $\phi(\textbf{x}) \neq \phi^\dagger(\textbf{x})$ be a complex scalar field, and let $\varphi(\textbf{x}) = \varphi^\dagger(\textbf{x})$ be a real scalar field. $\phi(\textbf{x})$ destroys a ...
1
vote
2answers
98 views

Phase shift in back-reflection generated at the mating point of two fibers

If you have light traveling from glass to air at normal incidence, e.g., in an optical fiber with the endface open, the Fresnel reflection coefficient would roughly be $R = |(1.5-1)/(1.5+1)|^2 = 0.04$ ...
2
votes
2answers
72 views

Thermographic camera - show for visiting school children

Next week a group of pupils (12-14 years old) will visit my institute. I would like to teach them about infrared radiation. Do you have any suggestion what kind of simply and impressive experiments I ...
3
votes
4answers
265 views

Liouville's theorem and preservation of topology

What might be a simple proof showing that the time evolution of the phase space volume can't lead to splitting off of the phase space volume? By Liouville's theorem, the total phase space volume is ...
2
votes
0answers
31 views

Why does a cyclist/motorcyclist bend when making a turn? [duplicate]

I've seen this very prominently in the Olympics
1
vote
1answer
130 views

Cobalt 60 beta decay

In the beta decay of an atom of Co60, the radiation you would expect is one or two gamma rays, plus an electron plus an electron neutrino (and in the nucleus Ni60+, if I understand it well). However, ...
1
vote
0answers
245 views

Gravitational potential energy and Center of Mass

I've been reading about the Nordtvedt effect, and how Gravitational Binding Energy (GBE) affects total mass. According to the WP article, experimental evidence rules out the existence of this effect. ...
1
vote
1answer
42 views

Dual and Multiple scattering of protons in light elements

I was wondering whether dual large angle scattering and multiple small angle scattering is of great significance in proton colision with light nuclei in comparison to heavy nuclei. For instance given ...
5
votes
3answers
315 views

Tensor product notation convention?

For two particle state, the Dirac ket is writren as $$\lvert\textbf{r}_1\rangle \otimes \lvert\textbf{r}_2 \rangle. $$ Then how do we write its bra vector, $$\langle\textbf{r}_1\rvert \otimes ...
3
votes
0answers
56 views

When Did Structures Begin to Orbit in the Universe?

In Big Bang Cosmology, I am familiar with the radiation era, and the moment of last scattering, but I am just not familiar with the physics of orbits, or of the “falling outward,“ if you will, that ...
0
votes
2answers
355 views

Does angular speed of the earth around the sun remain constant?

I presume that angular speed is nothing but angular velocity without direction. So, since the earth always takes nearly 365 days to complete one revolution around the sun, can't we conclude that it's ...

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