1
vote
0answers
4 views

Conventional flux in centrifuge?

The molecules are sedimentated in centrifuge, which is rotating with angular velocity $\omega$. The chemical potential of molecule (considering potential associated with centrifuge force) is: ...
1
vote
0answers
7 views

Number of States and Required Info for Bits vs Qubits

So with classical bits, if you have 2 bits, there are 4 possible outcomes that are possible. To determine these states, you only need 2 pieces of info, the state of each bit. With 3 bits, you can have ...
0
votes
0answers
4 views

Electrolysis of Paramagnetic Ferrous Chloride in Water

I'm trying to settle a bit of a debate between a friend and myself over the cause of an effect observed when dissolving Ferrous Chloride, Iron(III) Chloride, in water and supplying an electrical ...
-1
votes
0answers
12 views

Tensor raising and lowering

Just a quick question. I know: $V^{a}V_{a} = 1$ But wondered on the following: $V^{a}_{ab}$ Is it $1*V_{b} = V_{b}$ Or would I have to re-label V as it wouldn't be the same component?? Thanks!
0
votes
1answer
13 views

Friction Force and Applied Force for Acceleration

A person needs to move a 565 N object. The coefficient of static friction for the surface it's sitting on is 0.63. How much force is required to accelerate the object at an initial rate of 0.4 m/s2? ...
0
votes
0answers
21 views

Problem with commutator

My area is mathematics; however, told me about a problem that can solve with simple math, it says: Using $[\hat{J_{z}},\hat{O}]$, show that $\langle\alpha,j,m|\hat{O}|\beta,j',m'\rangle$ can be ...
2
votes
1answer
18 views

“Voyager: Lightning on Jupiter”: what's a sound source for this?

NASA created an official Soundcloud channel with a various sounds from missions. There are a Voyager: Lightning on Jupiter sound. Is there are ay information on how's this sound is produced (and ...
0
votes
1answer
23 views

Why is the voltage negative?

What I don't understand is why the the two voltage sources are subtracted when working out the emf for part a, The graph does not show the orientation of the solar panel so I thought I was to ...
0
votes
0answers
22 views

can there be an object which reflects( not illuminates ) electromagnetic waves in the non visible region?

can there be an object which reflects( not illuminates ) electromagnetic waves in the non visible region? If so then will it be appeared to us(humans who can see visible region only) transparent or ...
0
votes
0answers
7 views

Calculate rotational duration of magnetic levitation inside a vacuum chamber?

Background Numerous examples show rotating pyrolytic graphite (or similar diamagnetic material) that can be moved using a laser. Problem The problem has the following objects: An N52 grade ...
6
votes
0answers
25 views

What mechanism is responsible for the creation of these dunes on Comet 67P/Churyumov-Gerasimenko?

What mechanism is responsible for the creation of these dunes on Comet 67P/Churyumov-Gerasimenko? The following high resolution picture from ESA's Rosetta mission shows the dunes: At a distance ...
0
votes
1answer
19 views

Alternating Current/Electromototive Force equaling 0?

All alternating current diagrams are drawn as sinusoidal waves that intercept with x axis. Given our usual sine wave that equals to 0 at 180° it would mean the alternating current would equal to 0. If ...
1
vote
0answers
21 views

How does independence of the basic bras affect the choice of numbers used to represent a ket?

On page 54 of Dirac's book, The Principles of Quantum Mechanics, he states: Take an orthogonal representation with basic bras $\langle\lambda_1\lambda_2...\lambda_u|$, labelled by parameters ...
0
votes
0answers
7 views

Extracting times of hits from a composite detector response

I have a detector that registers a sequence of "hits" over a period of time. Each hit produces a signal that has the approximate form ...
0
votes
1answer
14 views

Sum of static and dynamic pressure in a tube constant?

The sum of static pressure and dynamic pressure is said to be constant along a streamline. Except for energy conservation reasons I don't understand why that is. Static pressure is proportional to ...
-4
votes
0answers
15 views

Principle of electrical machine by vk R mehta complete ebook needed [on hold]

I need the ebook for my exam on Wednesday(expecially dc generator and dc motor chapter)
1
vote
0answers
33 views

Tensor Notation Puzzle

I have hesitated to ask this question for fear of someone tagging it as a duplicate. It comes close to what others might have asked but I am looking for particular answers to this puzzle. Using ...
0
votes
1answer
26 views

Deriving electric field

Can anyone explain where the following expression for the electric field vector comes from? $$ \mathbf E(\mathbf r,t) = -\nabla \phi(\mathbf r,t) - \frac{\partial}{\partial t}\mathbf A(\mathbf r,t) ...
3
votes
2answers
30 views

Conceptual Question on Work and Potential Energy

I'm confused by classic description of work and negative work. If someone pulls (slowly) on a rope to lift a bucket in a well, I understand that the person is doing work on the bucket and gravity is ...
0
votes
0answers
37 views

Why does my metalic water bottle make noise?

I have metallic water bottle from Mountain Warehouse. An image of it is below. I fill it up and take a couple of swigs and I hear these random clicks and ticks after I set it down and other noises ...
4
votes
3answers
103 views

Is any energy required to deflect an asteroid, with force always perpendicular to its trajectory?

Let's assume there is an asteroid traveling on a straight line (far from any gravitational source), and we need to deflect it from its actual trajectory, so we build a rocket motor on the surface and ...
2
votes
1answer
12 views

Potential energy of Hydroelectric plant before the dam was built

So the energy potential of a Hydroelectric dam is the difference between the head and base. Before the dam was built where does all that energy go? I can understand that for a long valley that is ...
2
votes
2answers
18 views

Wave displacement with phase difference 180

The variation with distance x along a wave of its displacement d at a particular time. A second wave has the same frequency and speed as the wave shown in Fig. 2.1 but has double the intensity. The ...
4
votes
3answers
270 views

6 wheels more efficient than 4 wheels?

Which would be easier to push in a straight line, a flat cart with 4 wheels or the same cart (and same load) with the same size wheels, but has six wheels? and why? Thanks
0
votes
1answer
32 views

Gravitation Field inside hollow sphere [on hold]

for this homework problem I am trying to work out the gravitation field inside a hollow sphere. I have searched for a while now and haven't found a good post working it out thoroughly. One thing I ...
0
votes
2answers
32 views

How do the flow equations relate to the actual situation?

This question might seem silly but I'll try to make it clear. It's a question (I think) about partial differential equations systems in general, but since currently I'm studying fluid mechanics I'll ...
6
votes
4answers
1k views

How fast would someone have to run to travel vertically up a wall?

I am currently doing a physics project on the effects of so-called 'super-speed'.I was wondering how fast you would have to run to vertically travel up a wall? That is, to negate the force of gravity. ...
0
votes
0answers
4 views

PEDOT drying and polymerisation on air [on hold]

Have anyone tried to dry and polymerize PEDOT:PPS on air (usually it dryed in dry nitrogen, but we'd like to avoid our equipment modification)? What are the results?
1
vote
1answer
21 views

a charged particle path [on hold]

A particle of mass $m$ and charge $e$ enters a homogeneous and stationary electric field $E$ with velocity $v_0$ perpendicular to the direction of the field. Calculate the particle's path? What does ...
1
vote
1answer
15 views

Can iron be magnetized Via electric current in aqueous solution?

If you suspend iron particles in water and run an electric current through, the particles gather in a line along the current. Is this a form of magnetism?
2
votes
1answer
39 views

Finding potential energy of a solid hemisphere on top of another solid hemisphere [on hold]

A solid hemisphere with radius $b$ has its flat surface glued to a horizontal table. Another solid hemisphere with radius $a$ rests on top of the hemisphere of radius $b$ so that the curved ...
2
votes
0answers
24 views

Building a Faraday cage for mobile networks that is transparent for optical wavelenghts

A friend of mine is working on an architectonic project, where she designs a Faraday cage type of open space built in parks or other public places. The initial thought is to build it from some sort of ...
-2
votes
0answers
13 views

Can you tell/give me any websites about ship hydrodynamics? [on hold]

Can you tell/give me any websites about ship hydrodynamics?
0
votes
1answer
27 views

How long does analog to digital conversion take? [on hold]

I am analyzing Voltage signals from many channels which have passed through a multiplexer for analog to digital conversion, before reaching the computer. I am wondering how long the conversion takes, ...
1
vote
1answer
35 views

Can we extract chemical energy remotely?

To state directly. Can we use any electromagnetic method to extract energy from fat? Humanity store useless fat inside their body. And to work out mechanically leads to frustration of tireness and ...
0
votes
1answer
16 views

Interferometry works as a filter

I attended an astronomy seminar the other day and though I did not pick up much as it was on data collection etc, I did take away one sentence: "Interferometry works as a filter" Now I know what ...
0
votes
0answers
28 views

2 masses are attached to hanging string and one is released. What is the max height reached by the other? [on hold]

A spring is in static equilibrium (not moving) with two masses ($m_1$ and $m_2$) attached to the spring. The spring constant is: 22.0 N/m, while $m_1 = 0.16\,kg$, $m_2 = 0.13\, kg$ and mass 1 ...
4
votes
2answers
449 views

Does a force act on the body during collision

Consider two bodies A(black) and B(red) having equal mass. A is moving at a constant speed towards B, which is stationary. At certain point of time, they collide elastically, $\therefore u_{A}=v_{B}$ ...
-2
votes
1answer
30 views

Quantum mechanics: Finite square well problem

What will happen if the potential is less than 0, for instance $V(x)=-10eV$. Is this means there will be no bound states? Since solution to the time independent Schrodinger equation(those discrete ...
0
votes
0answers
11 views

Why is the heavy/light hole band not called heavy/light electron band?

Are the bands called heavy hole, light hole and electron band, just because the charge carriers are holes/electrons or is there some deeper reason I missed? The question might seem stupid, but it ...
2
votes
1answer
35 views

How is $\varepsilon_+^\mu(p) = \bar{v}(k) \gamma^\mu u(p)$ derived?

The relation $$\varepsilon_+^\mu(p) = \bar{v}(k) \gamma^\mu u(p)$$ is sometimes used to ease calculations of Feynman amplitudes with external gluons (see for example here at (2.13)). Where does this ...
1
vote
3answers
38 views

Can we harvest energy from constant gripping?

Gripping things hard needs energy even though nothing really moves. So I think we could harvest energy from this action, but I know that any type of energy harvesting requires moving parts. So can ...
-2
votes
0answers
14 views

what is variable mass of earth or center of mass? [on hold]

If we say the human being follow the law of conservation of mass. I agree then billon year ago the earth mass was in its bength which has came above so that means either mass along with its related ...
0
votes
0answers
25 views

correct tetrad index notation

There seems to be some different standards on the indexes of the tetrad. I am wondering which is the standard, which is correct, and which is an abuse of notation. In Sean Carroll's notes and in ...
3
votes
2answers
144 views

Water escaping from a pendulum bob, how is time period affected? [on hold]

well the question is: A hollow pendulum Bob filled with water has a small hole at bottom, through which water escapes at a constant rate. How is the time period(T) affected as the water flows out? I ...
0
votes
1answer
18 views

What are the advantages of Magnetocardiography?

I am reading the book Bioelectromagnetism by Malmivuo: Difference between the bioelectric and biomagnetic measurements lies in the sensitivity distributions of these methods. Diverse technical ...
1
vote
1answer
20 views

Is electricity constant in standard ECG device? [on hold]

I am reading the book Bioelectromagnetism by Malmivuo et al. I am thinking if you need to use Maxwell equations in electromagnetism of ECG device. I am not sure if you need to change the current ...
4
votes
1answer
64 views

What is the physical meaning of anti-commutator in quantum mechanics?

I gained a lot of physical intuition about commutators by reading this topic. What is the physical meaning of commutators in quantum mechanics? I have similar questions about the anti-commutators. ...
3
votes
1answer
54 views

Why does matter gather as discs around massive objects? [duplicate]

Why do discs, like rings of Saturn and the spiral shape of our galaxy form around massive objects, instead of just a (spherical?) cloud of matter?
0
votes
0answers
13 views

Conductivity Matrix (Symmetry Information)

I'm trying to understand the symmetry content of the conductivity matrix: one information is, presence of time-reversal symmetry causes the off-diagonal terms to vanish. When this is broken (e.g. in ...

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