0
votes
0answers
2 views

Gibbs isotherm and calculating interfacial tension change from first principles

Question: Is it possible for a solid particle to change the surface tension between two phases? (or: Does a solid particle have a chemical potential?) This question stems from the more ...
1
vote
0answers
9 views

Einstein's original papers predicting gravitational waves?

I came across the original handwritten papers in which Einstein predicted gravitational waves: and since LIGO announced they've detected a signal confirming the predictions I was wondering if ...
0
votes
0answers
11 views

Question on in and out states in chapter 10 of Weinberg's QFT volume 1

In chapter 10 section 2 (on pomology) of Weinberg's QFT volume 1, he shows $G$ has a pole when the external line goes on shell. In the proof, he inserted a complete set of single-particle states ...
0
votes
0answers
13 views

What is collimated/paralell beam of atoms?

This question is related to following exercise: "The intensity of the collimated, paralell beam of atoms of potassium was reduced by 3% by a layer of argon at 1 mm thickness and pressure $6,0\cdot ...
1
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0answers
13 views

Does gravitational time dilation have a direction?

I understand that higher the gravitational potential, "slower" time runs. So a clock on international space station will run "faster" than a clock at sea level. However does it matter where the ...
1
vote
0answers
10 views

Question about a solution of a partial differential equation by separation of variables

I'm trying to understand this text: http://www.ekayasolutions.com/UCDMath/HeatCondSphere.pdf But I'm having problem with this part: Whe have to solve: \begin{equation} \dfrac{\partial ...
-1
votes
0answers
15 views

What happens to the average kinetic energy if you double the temperature?

I've always wondered what would happen to the average kinetic energy if you double up the absolute temperature of an ideal gas. My hypothesis is that, since the temperature is proportional to the ...
1
vote
1answer
12 views

Why does narrower slit give a wider diffraction pattern in single slit diffraction?

I was reading on this website and it said that one of the characteristic of single slit is narrower slit give a wider diffraction pattern but why? ...
1
vote
2answers
23 views

Graviton and photon

I understand that photon is the carrier of a change in the EM field. Is the graviton a carrier of the gravitational field itself or a carrier of a change in the gravitational field?
0
votes
0answers
4 views

Diffraction grating location of maxima for arbitrary number of slits

Say I have a diffraction grating with 8 slits. I want to find the location of the maxima. What do I do? Can I use the equation $d\sin\theta = n\lambda$? I know it works for 2-slits and for ...
1
vote
0answers
3 views

Effect of paint on drag force

Aerospace engineering as well as automobile engineering gives a particular significance to the shape of a vehicle to enable proper and more effective transportation.What I want to know, is, about the ...
3
votes
1answer
44 views

So Black Holes Actually Merge! In 1/5th of a Second - How?

I've read a lot of conflicting answers in these forums. However, today saw the awesome announcement of gravitational waves. Two black holes merged: ...
0
votes
0answers
5 views

If the torsion of the straight line is undefined what happens with the information about the torsion?

If the torsion of the straight line is undefined what happens with the information about the torsion? It is known that the information conserved in a system can be nor created, neither destroyed. ...
0
votes
0answers
8 views

Quadrupole configuration

The general solution to the 2D Laplace equation, $\nabla^2 \psi = 0$ is \begin{align} \psi(r,\theta) = P_0 \ln r + \sum_{k = 1}^\infty \dfrac{Q_k \cos(k\theta)+R_k\sin(k\theta)}{r^k} \end{align} The ...
2
votes
2answers
40 views

Why is the speed of light exactly $299,792.458$ m/s and not faster or slower?

Why is the speed of light $299,792,458$ metres per second, and not faster or slower. Why not $500$ trillion kilometers per second or $120$ miles per hour? This has been 'bothering' me for a while. ...
-1
votes
0answers
6 views

How do we acquire c-coefficients (“weights”, “probabilities”), when dealing with superposition of stationary states?

I searched quite a lot textbooks to answer this question, but I couldn't find anything satisfactory. This could be more general question, but it will be easier to just restrain to particle (say ...
1
vote
0answers
17 views

Are there waves of time?

If I understand correctly, gravitational waves are ripples in the fabric of space-time itself created by the movement of mass. Moreover, space and time are just dimensions of the same space-time ...
1
vote
1answer
30 views

Is there absolute proof towards gravitational waves?

As you probably know gravitational waves seem to have been proven unless you've been living under a rock for the past day. The experiment involves the reflecting off mirrors and waves of light and it ...
0
votes
0answers
9 views

How much light is necessary to form a black hole [duplicate]

I suppose that enough light in a small enough volume could create a black hole. What is the good quantity that can tell when light can or cannot make a black hole? Energy density? But there must be ...
1
vote
1answer
16 views

Does the size of a black hole change depending on its charge or spin?

I was talking to this friend of mine who said that the size of a black hole could vary depending on its "charge" and spin. He said the size of a black hole would reduce if it had a spin or charge. The ...
0
votes
1answer
5 views

Question about the way the inner stress in an axially loaded member is defined

When a member is in tension, such as in a tensile test of a piece of metal, its freebody-diagram would show a force of P in both directions. Why then is its internal stress not $\frac{2 \cdot P}{A}$? ...
0
votes
2answers
31 views

Confusion over basis sets in quantum mechanics

In a sense, I feel like I understand every step in the following (fairly typical) calculation, but I don't understand the conclusion. I consider a vector space spanned by two basis vectors ...
1
vote
2answers
80 views

How strong were the gravitational waves that LIGO detected at the source?

Congrats to the LIGO on the announcement of their discovery of gravity waves! The articles I've read say that the distortion we see here is much smaller than a proton. What about at the source? Would ...
2
votes
2answers
75 views

What will be the role of gravitational waves in future physics? [on hold]

What does this discovery mean for us? Can it lead to a better understanding of the cosmos?
-2
votes
0answers
19 views

Find the period of a pendulum system

How to solve the following problem, A mathematical pendulum is formed by a cable with length $l$ and a sphere at it's end with mass $m$. While the pendulum swings at it's position of ...
0
votes
0answers
5 views

Rotational spring in inertial reference with Euler angles

I am thinking about how to exprime the moment produced by rotational springs using the Euler angles. Consider a rotating rigid body A, a local reference $B$ $(o,x,y,z)$ is attached at the center of ...
1
vote
1answer
11 views

Example of a system where we cant measure the total possible microstates of a system but can measure the microstates of most probable state?

I have been reading about entropy and I read that entropy is basically a measure of total possible microstates but there was an approximation that when no. of particles become very large we take ...
4
votes
0answers
54 views

How were gravitational waves discovered?

It was announced today that gravitational waves were discovered. The article gives the following explanation of the experiment: When a gravitational wave passes LIGO, the tunnels deform ...
2
votes
1answer
6 views

How is the energy spectrum of a gamma ray in a material?

I'm trying to solve the following problem for a course in radiation physics. A thin ray of intensity $I_0$ and energy $E_0$ impacts in a material. What is the intensity and the energy of the ...
1
vote
0answers
7 views

portable battery packs for decorative lights

I a set of home decorative lights that is powered by a portable 2 x D cell batteries. Can I replace the current pack with a new pack that takes AA batteries
0
votes
1answer
19 views

If the electric potential is location dependent, why do charges loose it when passed through a heavy resistor in a circuit?

I really cannot understand this: I know through reading that unlike electric potential energy, which is charge dependent, the electric potential is purely location dependent. For example: If at a ...
-5
votes
0answers
32 views

The question is related to quantum mechanics

The energy gap in germanium is 0.72 eV. Find the maximum wavelength of electromagnetic radiation which can cause transition from the valance band to the conduction band.
1
vote
1answer
39 views

How many bits of information can be stored in an atom?

How many bits of information can be stored in an atom? The atom in question being as big as you like, but must be stable with regard to nuclear decay
0
votes
0answers
12 views

How to determine the basis of any crystal

In the following example, I have a rutile TiO2. Here the basis of O with respect to Ti is (0.3*x, 0.3*y, 0*z), where a,b,c are the lattice vectors. So in order to build a crystal, I need the basis and ...
2
votes
1answer
31 views

flux quantization in superconducting ring

I am trying to understand SQUID microscopy from the ground up, so I am starting with flux quantization in superconducting rings. I found a nice presentation that covers some of the details, but I am ...
-1
votes
4answers
34 views

People went down two different length slides end up at the bottom at the same time

Discussion I am having: If there are two slides that are at the same height. One slide is 100m long and the other slide is 200m long. The endpoint and start point are the same displacement. In a ...
0
votes
0answers
8 views

View factor of two parallel coaxial *rectangular* plates

I've found a lot of tables and resources that list view factors (VF) for various geometrical configurations, but I couldn't find a single one that has the VF for two parallel coaxial rectangular ...
-1
votes
1answer
17 views

Calculate the pressure in a container given moles and volume

Say there are two containers with the same volume. The first has a temperature T and pressure P and contains 1 mole of $O_2$. The second has a temperature 2T and contains 1 mole of $He_2$. I'd like to ...
-1
votes
1answer
32 views

Why can an electric field escape from a black hole?

I know this is a duplicate question but the other answers didn't explain clearly my problem. The talkes about no hair theory for explaining the communication and information problem of matter inside ...
0
votes
0answers
9 views

Flux through a face of a cube for an arbitrary position of a charge

Consider an imaginary cube with edge length a in space. A charge q is placed at the centre of one of the faces of the cube. So, what is the electric flux through the face opposite to the charge? ...
16
votes
2answers
883 views

Why is the detection of gravitational waves so significant?

Since there is to be an announcement about this today, I was wondering what the significance was of detecting gravitational waves. I know it is another confirmation of GR, but I thought we had already ...
0
votes
1answer
6 views

electric potential and other potentials

We know that without potential difference no electric current can flow.If two conductors carrying positive and negative charge respectively then the first one will have positive and the rest one will ...
0
votes
1answer
14 views

Relation of conformal symmetry and traceless energy momentum tensor

In usual string theory, or conformal field theory textbook, they states traceless energy momentum tensor $T_{a}^{\phantom{a}a}=0$ implies (Here energy momentum tensor is usual one which is symmetric ...
1
vote
1answer
25 views

Deriving Boyle's law from only the Gay-Lussac laws

My physics professor during a lecture presumably mathematically derived Boyle's law from the two Gay-Lussac laws for ideal gasses. What he said is also printed in his own textbook. He states that, ...
0
votes
0answers
14 views

Polka dot beamsplitter. Is it good for gaussian beams

I am doing pump probe and I am looking for beam-splitter which will not affect beam polarization too much, as I intend to measure polarization dependencies. I have heard of polka-dot beam-splitters ...
0
votes
0answers
9 views

Energy, Power, normalized time-series [on hold]

Given the following (productino of an energy-plant): Total energy production for a year (in Wh) Normalized hourly production ( 0 - 100%): For every hour a value: 100% means full production; 0 % ...
3
votes
0answers
25 views

Why do we assert Hulse–Taylor binary system's orbital decay to gravitational waves and not radiation?

From https://en.wikipedia.org/wiki/PSR_B1913%2B16#Star_system The Hulse–Taylor system's orbit has decayed since the binary system was initially discovered, in precise agreement with the loss of ...
-2
votes
1answer
33 views

Is Lorentz Invariance necessary for Maxwell Equations?

An example shows that Maxwell Equations should not have Galilean invariance, therefore Lorentz Invariance is not needed for Maxwell Equations. The example: In a train moving at a constant speed ...
0
votes
0answers
7 views

Heat and mass transfer modes inside rapidly rotating cylinder

My question is about simultaneous heat and mass transfer in rotating cylinder system. System can be detailed as: A rotating cylinder contains wet porous substance in a lump shape. Air stream enters ...
0
votes
0answers
27 views

When is the spin of an electron changing?

An electron can have a half spin up or down. The up spin can become a down spin to lose his weak charge. But when are electrons changing their spin?

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