1
vote
1answer
22 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
16 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
45 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
26 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
16 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
36 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
17 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
39 views

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

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
477 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
46 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
39 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
43 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
15 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 ...
3
votes
1answer
83 views

Correct tetrad index notation

There seems to be some different conventions 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
149 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
20 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
94 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
55 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?
1
vote
0answers
16 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 ...
1
vote
1answer
20 views

Questions about the formula used to determine inductive reactance and $Z_t$

I am currently on the inductors unit in my Navy schooling and I have two questions about these formulas that I learned about. As I'm aware, the ability of an inductor to concentrate a magnetic field ...
2
votes
1answer
42 views

Confused about gravitational potential energy [duplicate]

So learning the concept of gravitational potential energy, my professor says that when lifting an object without any acceleration, the force we exert on the object to lift it is the same as the force ...
1
vote
1answer
14 views

Direction of induced EMF(and current) and Lorentz force direction?

Is the right hand rule for the Lorentz force (given the current and magnetic field directions)and the direction of induced EMF the same?
2
votes
2answers
56 views

Is superposition principle equally valid for both scalar and vector quantities?

I was wondering if superposition is even applicable to scalar quantities because scalars should simply add up to give final result as there is no sense of direction. Do we have any example of a vector ...
1
vote
0answers
39 views

How to prove that the net magnetic force in an arbitrary current loop is zero [on hold]

I believe that using Stokes' theorem makes this a laughing matter, because $$\mathbf{F}=\oint_C i d\mathbf{r} \times \mathbf{B}$$ Since the magnetic field is constant the $\nabla$ operator would ...
0
votes
0answers
28 views

How to calculate how much air is leaking out of an object?

I have a pressurated pvc pipe. I am wondering how long it would take for it to leak out on a small tube. I really just want to know how to do the equation, so I could figure it out depending on the ...
3
votes
1answer
46 views

Super Strong Magnets

I've seen the size of electric motors get smaller over the past 10-15 years...especially those used in small remote control vehicles like helicopters. I heard that the magnets being used in the ...
0
votes
0answers
17 views

Trying to calculate the length of a tube to heat Ar gas

If one were trying to heat Argon gas from ambient (~20C) through a mild steel tube of some diameter 'd' how long would it need to be? Additional unknown includes flow rate of Ar gas so some general ...
4
votes
3answers
163 views

Why is $\pi$ used when calculating the value of $g$ in pendulum motion?

I am trying to intuitively understand why $\pi$ is used when calculating the value of $g$ using the harmonic motion of a pendulum: $$g ~=~\frac{4\pi^2L}{T^2}.$$ Does it have something to do with the ...
-1
votes
0answers
18 views

Finding net force [on hold]

Buoyancy and high altitude ballooning. Buoyant forces are supplied by every fluid (liquid or gas), it’s the mechanism that sends high altitude balloons all the way up to the stratosphere. For gases, ...
1
vote
1answer
66 views

Interaction pictures of Quantum Mechanics

I want to understand the Schrödinger, Heisenberg and interaction picture and have a few questions about them: So in general you have a time-dependent Hamiltonian $H$, as for example the potential may ...
0
votes
0answers
10 views

Addition of forces in dielectric material

In this paper (page 2 of document) it is said that: Because this calculated force was comparable to the gravitational force, they assumed that the same would be true for the forces on a ...
2
votes
1answer
56 views

Why do vapour cones form around jet fighters?

Apparently this phenomenon has nothing to do with jets breaking the sound barrier and has something to do with the Prandtl-Glauert singularity as described on Wikipedia. But, the Wikipedia article ...
1
vote
0answers
34 views

Projectile motion, solved with perturbation theory [on hold]

A ball is dropped from rest, the initial height is $h_1$. There is air resistance given by $-mkv$. In the downward motion, the equation of motion can by written as $$\dot v = -g-kv$$ with the y ...
2
votes
0answers
26 views

Discrete Symmetries: Breaking and Preserving

This is not a question, let's list down all the effects resulting from breaking or preserving of various discrete symmetries, on various observables, be it in condensed matter or in high energy. ...
0
votes
1answer
40 views

Atom in a box and collapse of the wave-function

Suppose I have an atom trapped in an optically transparent box. I'm assuming the atom is bouncing off of the walls and not bonding, i.e. the center of mass of the atom experiences a square well. Now ...
2
votes
1answer
44 views

Coupling of matter field with gauge boson and Goldstone boson:

What's the fundamental difference between the way a gauge boson gets coupled to a matter field, preferably a Fermionic field and the way a Goldstone boson gets coupled to the matter field ? In ...
0
votes
0answers
19 views

Finding most/least tension between 5 cars attached to a train [on hold]

I am currently doing Grade 11 physics and I have been troubled by this one question for homework for quite a while. Hopefully most of you will be able to help me out. Question: A 40,000kg train ...
0
votes
0answers
23 views

Calculate the density of this liquid and determine general formula for finding density of a liquid [on hold]

a) A 3.8 kg aluminum ball is found to have an apparent mass of 1.9 kg when completely submerged in a particular liquid. Calculate the density of the liquid. b) Determine a general formula for ...
1
vote
4answers
254 views

Having trouble understanding some stuff about delta functions [on hold]

I was going through one of the examples in Griffith's Quantum book and there was a few things in Example 3.3 that I didn't understand that I was hoping to get some clarification on. For instance, we ...
2
votes
0answers
45 views

Physical reasoning and mathematical problems [on hold]

After reading The Mathematical Mechanic: Using Physical Reasoning to Solve Problems by Mark Levi, I was wondering if there there are other books (or papers) that use a similar approach to explore ...
1
vote
1answer
39 views

Concerning the transtition between matter dominated universe and radiation dominated universe

What caused the transition, and how to we know that this did not warp our calculations for the age of the early universe ?
0
votes
0answers
32 views

Covariant Nonlinear Transformation in two inertial frames [on hold]

I read about Lorentz transformation in my old lecture materials: and I started to think what would the matrix/tensor (or other structure, no matrix presentation exist, since matrices are linear) be ...
-4
votes
2answers
57 views

What will happen if a hairdryer is turned on in an air tight box?

I wanted to know what would happen if a hairdryer is turned on in an airtight box
0
votes
0answers
16 views

Why does it appear that a Carnot Engine is allowed to reject less heat when $T_H$ is increased?

I'm struggling to understand a consequence of the definition of the thermodynamic temperature scale: $$\left( \frac{Q_H}{Q_L} \right)_{\mathrm{rev}}=\frac{T_H}{T_L}$$ This equation is valid for a ...
0
votes
0answers
24 views

Are complex planes (Gaussian plane) examples for a Hilbert Space?

My assumption: Yes, even though from physical application point of view it looks like different. (A complex plane is used in complex AC analysis, while Hilbert Space refers usually to QM.)
-3
votes
0answers
25 views

Is time relative to the speed you are traveling [duplicate]

Is time relative to the speed you are traveling.. What happens when you reach the speed of light?
2
votes
0answers
20 views

Behavior of Parahydrogen in a Magnetic Field

At low enough temperature, at equillbrium, the dihydrogen molecule is predominately parahydrogen, with the spins of the two protons opposite. Does an external magnetic field alter the ortho-para ...

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