0
votes
0answers
2 views

pressure on a sealed vessel

If a sealed vessel can withstand being submerged to 2 atm external pressure with 1 atm inside, is this the same as the vessel at 1 atm with high vacuum within the vessel? Sorry, I know this should be ...
0
votes
0answers
24 views

What makes a matrix a tensor in special relativity?

Is any matrix a tensor in special relativity? My question is inspired by the definition of the electromagnetic field tensor in Carroll's Spacetime and Geometry book. In equation (1.69) he defines a ...
0
votes
0answers
12 views

String-like theory

What is the general theory that describes the interactions between strings. I mean the basic object in the theory is (closed) string and they have interactions among them. The string theory, as I ...
0
votes
0answers
6 views

How to determine the pressure of the moving water at the bottom of a vertical pipe [on hold]

Water is flowing upwards in a vertical pipe with an inside diameter of 0.06 m at a velocity of 0.0152 m/s. The length of the pipe is 0.5 m. What is the pressure at the bottom of the pipe? Density of ...
0
votes
0answers
13 views

Phase space volume and correlation dimension

This may seem trivial but I will appreciate help in determining the functional form of the probability density function (pdf) for the following case. Will highly appreciate some guidelines on how to ...
1
vote
1answer
37 views

Interpretation of $\vec{x}$ in QFT

I am still at an early stage of studying QFT (QFT in a nutshell by A. Zee), and maybe (and maybe not..) the answer to this question would emerge from the text book/s later, but, I'm still going to ask ...
0
votes
0answers
15 views

How to calculate Gibbs free energy of diamond?

How the effect of crystal structure on Gibbs free energy is calculated? For example, how the Gibbs free energy of diamond is 2.9 kJ/mol, while that of graphite is 0?
2
votes
1answer
27 views

How is taking the average of an integral over an interval justified?

I have been studying classical mechanics and often when going through a worked problem I see a step where there is an integral from 0 to 2$\pi$ of $\sin^{2} \theta \ d\theta$. Instead of using the ...
0
votes
0answers
9 views

Specific volume of an air parcel [on hold]

So I have an unsaturated air parcel in the atmosphere that ascends adiabatically from the $1000$ mb level to the $700$ mb level with it's initial temperature being $10$ degrees Celsius. I have to ...
2
votes
1answer
12 views

Units of acceleration & Newton's 2nd Law

I tried to use Newton's second law, $F=ma$, to calculate the acceleration of an object, what am I doing wrong ? \begin{align}\frac{F}{m}&=\frac{ma}{m} \\ a&=\frac{F}{m}=\frac{30\,\rm ...
1
vote
1answer
36 views

If I squeeze something really hard, will it ever become two-dimensional?

A mosquito just wanted to bite me! Päng - and it stuck to my hand, hardly recognisable anymore. I said to my girlfriend: "Just reduced the dimension of the mosquito by one!" Therefore the question: ...
4
votes
0answers
25 views

Density matrix formalism and group representation

The postulates of quantum theory can be given in the density matrix formalism. States correspond to positive trace class operators with trace 1 on a Hilbert space $\mathcal{H}$. Composition is defined ...
3
votes
1answer
282 views

Does gravity affect magnetism, vice-versa, or do they “ignore” each other?

I am suddenly struck by the question of whether gravitation affects magnetism in some way. On the other hand, gravity is a weak force, but magnetism seems to be a strong force, so would magnetism ...
1
vote
1answer
65 views

Complex Quantum Wave

Can we explain complex nature of quantum mechanics in the following way? Experimentally we do know that quantum particle behaves like a wave, but generally particle is well defined in space and can ...
0
votes
0answers
11 views

how do I resolve this velocity into components? [on hold]

my problem is: And this is the diagram I drew to resolve it into its constituent R and theta forces: So I get \begin{align} V_r &= - V \cos \theta \\ V_\theta &= V \sin \theta ...
1
vote
2answers
28 views

What will happen in principle if one tries to push a neutron star?

When we push an object it moves due to the mutual repulsion between the electrons in our hand and the electrons in that object. Since a neutron star contains only neutrons, what will happen in ...
1
vote
1answer
34 views

How does Dirac form this conjugate imaginary equation?

On page 30 of Dirac's book $$\xi|P\rangle = a|P\rangle\tag{12}$$ He then says Suppose we have a solution of (12) and we form the conjugate imaginary equation, which will read $$\langle ...
-2
votes
0answers
14 views

Michelson-Morley Experiment, Time Dilation, Length Contraction assignment need help [on hold]

I have Physics assignment about Michelson-Morley Experiment, Time Dilation, Length Contraction need help. The question are in the pictures Thanks
0
votes
0answers
12 views

Packing fraction of atoms in a HCP structure

I am looking to find the ratio of atomic sphere to unit cell volume in a HCP (hexagonal close packing) arrangement. Some sources I have say it is 0.74 My unit cell structure is that shown below. I ...
2
votes
1answer
30 views

What is relationship between Quantum tunnelling and Gravitational potential energy of stars?

Are there a direct mathematical relationship between Quantum tunnelling and Gravitational potential energy of stars? The true source of the Sun's energy was shown by Hans Bethe to be nuclear fusion ...
3
votes
0answers
47 views

How can you accurately determine your own mass?

I'm trying to figure out whether it is possible for an individual to accurately determine his/her own mass, to within 100g, using equipment that is readily accessible or can be purchased at a ...
0
votes
0answers
17 views

The shape of water column flowing from tops [on hold]

My question is what are the useful to study about the shape of water column flowing from tops?
0
votes
0answers
12 views

Constant Rayleigh Scattering Cross Section

in the Review of Particle Physics - Interactions of Particles with Matter, there is a plot that gives the cross sections for different interactions of photons with matter. One of them is Rayleigh ...
8
votes
1answer
545 views

How close can you get to lava before burning?

As the title asks: How close can you get to lava before burning? I know that it depends on an number of factors; speed of lava flow, wind direction/strength, type(?) of lava flow (related to speed, ...
3
votes
2answers
79 views

Transition amplitudes by functional methods in QFT

I am following section 9.2 in Peskin and Schroeder in which the Feynman rules are derived for scalar fields. They define (in eqn (9.14), page 282) the transition amplitude from $\vert\phi_a\rangle$ ...
1
vote
3answers
120 views

Asymmetric heat conduction?

So I have this side-view drawing. Now I wonder, will such a multi-layer material have asymmetric heat conduction properties? Namely, because of radiative conduction, reflective aluminum surface ...
2
votes
2answers
50 views

Definition of Entropy in thermodynamics

In most textbooks, the definition of entropy in reversible processes on a system $S$ is given simply as $$d S=\delta Q/T.$$ It seems to me this definition is insufficient since it does not specify ...
1
vote
1answer
9 views

The strength and control over the strength of electromagnets, correlation between the strength and weight of the magnets

I am currently working on a project that aims to use the attraction & repulsion between two electromagnets as an alternative to weights, from a physiotherapy and rehabilitation perspective to help ...
0
votes
1answer
24 views

Calculating change in gravitational potential energy [on hold]

A satellite mass 500kg is elevated from altitude 10000km to altitude 20000km. Radius of earth is 6378km. Mass of earth is 5.97 * 10^24kg. Gravity is given to be 9.81m/s My attempt is using final mgh ...
1
vote
0answers
23 views

Estimate the maximum distance of water spatter

There is a faucet dripping water from height $H$ onto a smooth, horizontal ceramic surface, and I need to give a upper bound of the maximum distance between the water spatter and the point directly ...
0
votes
1answer
15 views

The head start, or, Rear clock ahead

Two clocks are positioned at the ends of a train of length $L$ (as measured in its own frame). They are synchronized in the train frame. The train travels past you at speed $v$. It turns out that if ...
0
votes
0answers
15 views

Determining if an object is dielectric or metallic

In a worksheet I was given, I had to find the net electric field of P which is L distance away from a bar. The last question is ...
0
votes
1answer
27 views

How to model mechanical systems that change configuration over time?

If I have some simple mechanical system, say - a mass attached to one end of a spring fixed at the other end, I can write differential equations describing such systems which can also be handled ...
11
votes
1answer
684 views

Why is the shape of lightning or an electric spark a zig-zag line?

Why is the shape of the lightning (or an electric spark) always of a zig-zag nature? Why is it never just a straight line? Image source.
2
votes
0answers
20 views

Can this simple spectrometer be precise without collimation?

Consider the following spectrometer structure: Here the slit can be changed in size, and the lens and detector can be moved closer to or farther from the diffraction grating. I was trying to get ...
1
vote
0answers
19 views

Why are the eigenvalues of a linearized RG transformation real?

The RG transformation $R_\ell$ maps a set of coupling constants $[K]$ of a model Hamiltonian to a new set of coupling constants $[K']=R_\ell[K]$ of a coarse-grained model where the length scale is ...
1
vote
0answers
24 views

Placing small spheres on the surface of a large sphere [migrated]

I need to cover the surface of a large sphere ($R$) with small spheres ($r$), where $R$ and $r$ are the radii of the large and small spheres, respectively. Can someone indicate an algorithm that can ...
1
vote
2answers
22 views

Loads in decelerating a falling object

I'm new here and haven't looked at physics in any real depth since high school, 8 years. so apologies for any obvious mistakes. I remove trees in confined spaces setting up rigging systems, I am ...
1
vote
2answers
34 views

Is stethoscope sound mono- or stereosound?

I am curious if the sound is monotonic. There are two things on my ears however. Is stethoscope sound mono- or stereosound?
1
vote
1answer
38 views

Equation of motion for system of springs

I need to find the equations of motion for the following system. If $x_1$ is $m_1$'s extension and $x_2$ is $m_2$'s, then, I feel like for $m_1$ we just need to consider $x_1$ giving $$m_1 a_1 = ...
0
votes
1answer
26 views

Muon and Strong interactions

The strong forces operate up to range of 10^{-15} meter. The calculations for Muon reveal that they can be propagator for distances up to 10^{-14} meter. Why can't I ignore the factor of 10 and call ...
1
vote
0answers
27 views

How can I calculate the rotational force and motor HP needed to lift a 5lb sheet from a horizontal position to a vertical position from one end?

Essentially, I need to know the following: How do I calculate the rotation force along a fulcrum? Is there an equation? What is the weight of a 5 lb object at the fulcrum if the fulcrum is located ...
4
votes
1answer
72 views

Symmetry factor and coupling constant in scalar field theory

I am just now starting my particles "education" so forgive me if this is elementary... Looking at interaction terms in a scalar field Lagrangian, I get: $$ ...
1
vote
0answers
19 views

Relationship between plasma physics and quark gluon plasma

To what extent do the ideas common in modern plasma physics, such as magnetohydrodynamics, cold plasma models, common types of plasma waves, Maxwell's Equations, etc, relate to the study of quark ...
3
votes
0answers
32 views

Textbooks on algorithms for the perturbative calculation of High energy physics

For the perturbative calculation of High energy physics, I have known some packages such as FeynArts, FeynCalc, MadGraph, CompHEP, GiNaC, and so on. But I am wondering whether there exists a textbook ...
3
votes
2answers
28 views

Forces on objects orbiting a black hole?

Firstly, please excuse my elementary knowledge and lack of eloquence when writing about astrophysics. I am a dentist, who occasionally thinks about the how the universe works. I'm both fascinated and ...
1
vote
1answer
24 views

Why is the current in an electric circuit constant?

Considering electrostatics, suppose we have two charges of equal value and opposite sign and we put electrons along the road between them: We know that the electrical force or field is different from ...
2
votes
2answers
33 views

Observing a particle over a certain domain

I was just thinking: in Quantum Mechanics, we start out with that whole collapsing business by observing the x position of a particle. I was thinking: why do we have to do that? What if we only ...
2
votes
1answer
20 views

Energy loss in the photoelectric effect

If a photon hits an electron with an energy that is less than the energy required to change the energy level of an electron, what happens to the energy of the photon (is it not absorbed and just pass ...
1
vote
0answers
17 views

flow through an orifice [on hold]

The surface area of a first orifice with 2 mm diameter is 3 mm$^2$. The surface area of a second orifice is 5 times bigger from the surface area of the first orifice (15 mm$^2$). How much would be ...

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