0
votes
3answers
3k views

How is a potential difference created between two points?

I would like to know how potential difference is created between two points?Is potential difference created by adding more electrons at one side?If that's the case how to add more electrons at one ...
-1
votes
0answers
23 views

A few questions related to bernoullis principle & fluid dynamics in a pipe

I've been struggling with a few things as i've been introduced to bernoulli's principle, hopefully someone can help me clear things up(in somewhat plain, easy to understand language) In the examples ...
0
votes
0answers
12 views

Expectation value of an Observable and Eigenstates

I am learning about Quantum Mechanics at the moment and I was wondering about Eigenfunctions and Observables. The question I would like to ask is, If a wavefunction is not an eigenstate of an ...
0
votes
0answers
7 views

How can we look back at our Universe 13Billion years ago?

I read this article on Space.com and I quote "As far as we know, that's as far [back] as we can see — we get an image of the universe as it was when it was about 389,000 years old," So what I wanna ...
14
votes
3answers
2k views

How is the number of electrons in an atom found?

I was wondering, what type of experiments were held to identify the number of electrons in an atom? (For example, how do we say that carbon has 6 electrons and magnesium 12.) I would like someone to ...
12
votes
2answers
361 views

Relationship between Mars and Earth rotation

Is it by pure random chance that Mars and the Earth have nearly the same day duration (Mars day is barely 40 minutes longer, which is just 3% difference), or there is some causal relationship between ...
0
votes
0answers
6 views

This might make no sense light is time

I've done a lot of research on time I think when light/color is absorbed it is giving off as time and when it is going fast the light can't keep up
10
votes
13answers
369 views
+50

How to pour water from a bottle as fast as possible

When one pours water out of a bottle, it first flows smoothly but then a pressure 'blockage' develops and the pouring becomes interrupted and turbulent, so that the water comes out in splashes. This ...
4
votes
1answer
152 views
+100

Electric Potential Field of Parallel Electrodes within Grounded Shell

Any help would be greatly appreciated I think I need to solve this using boundary potential conditions and Laplace equations. Here is the system I'm attempting to model: The red rods are metal ...
-2
votes
0answers
6 views

Expansion Of Universe : On the Basis Of Aether Theory

I would like to ask that in the recent experiment of discovering Gravitational Waves scientists have also found or believe that they have found the evidence of Dark Matter. So if dark matter is made ...
0
votes
0answers
6 views

Understanding stress-strain calculations

I'm trying to compute calculate the stress-strain curve for an elastic material with cylindrical geometry subject to an increasing uniaxial load. I understand that this requires: stress = $F/A_0$ ...
1
vote
2answers
2k views

Why does time dilation cause you to age slower? And is time considered relative to the observer?

I understand that the higher your velocity the slower light will move. But how does time itself slow down while you are moving faster?
0
votes
3answers
22 views

Charged Particles: How is energy conserved?

I can seem to understand where the energy comes from when two particles accelerate. I tried searching through the forums and it seems like the answer is always potential energy was the source of ...
1
vote
0answers
45 views

How to plot numerically the wave functions according to the Hamiltonian?

It is often difficult to analytically solve the Schrodinger equation, and so we need to obtain a solution numerically. An example plot is shown below. Here, the wave functions for a three junction ...
0
votes
4answers
6k views

Why does resistance increase with length?

This is for the case of wires only (pipes are easy). I see that if I place a 9-Volt (constant) battery across any wire, the current is proportional to resistance. I don't understand why, for a ...
2
votes
3answers
45 views

Does curved spacetime change the volume of the space?

Mass (which can here be considered equivalent to energy) curves spacetime, so a body with mass makes the spacetime around it curved. But we live in 3 spatial dimensions, so this curving could only be ...
0
votes
1answer
102 views

Quantum Dimer Model (QDM) hamiltonian

The Hamiltonian given by Rokhsar-Kivelson QDM is based on tensor products of the state vectors. Why is this the case?, is it because the lattice model is a mixed state? It'd be great if someone could ...
0
votes
0answers
11 views

Resistance increase with length because of more scattering?

I am referring to one of the answers to this old question. I can't add comment to it because I don't have enough reputation. So here I rephrase the question: does resistance increase with length ...
0
votes
1answer
17 views

Can large bodies spin both ways

Can a planet, stars, moons, solar systems or black holes rotate on 2 axis? and if so is it possible to have 3 or 4 axis? Two axes for rotational motion does not cover if planets can hove 2 axis in a ...
2
votes
1answer
57 views

Does a scale weigh a bee flying inside a box?

This question is very similar to this one or even this one except some minor differences... The box is much larger than the bee. The box has no top cover The bee is flying still in the middle of the ...
0
votes
0answers
12 views

At what direction does a ray reflect at a 90 degrees corner?

Say we pointed a laser that is projected into a $90^{\circ}$corner of a mirror made by perpedicular walls. I know that you cant use tangent since a derivative of boundary of mirror would not exist ...
-4
votes
1answer
26 views

Cosmological Significance of Uncertainty

Is it fair to say that quantum uncertainty is the most fundamental and primordial characteristic of the universe? Wouldn't uncertainty have predated the initial expansion of spacetime, and not be ...
0
votes
1answer
13 views

Find the initial velocity's angle of a projectile knowing only the ratio between the horizontal distance traveled and max height

The ratio between the horizontal distance traveled and the launch height is 3 to 1. I think it is possible to find the angle given this information, but how exactly do you do it? I think it's arctan(2/...
1
vote
2answers
160 views

Quantum probability of entangled spin-1/2 particles?

Let us say that you have two entangled spin-1/2 particles (entangled in such a away that angular momentum is conserved). Let us say particle 1 moves to the left and particle 2 to the right. We measure ...
-1
votes
0answers
10 views

How are the charges on the plates of a capacitor distributed?

Given a specific overall amount of energy a rectangular parallel plate capacitor stores what number of atoms on a specific plate would have any given specific charge?
3
votes
2answers
102 views
+50

Static vs Dynamic pressure

According to Bernoulli's law, the narrower the tube where the fluid is flowing the lower its static pressure and the higher its dynamic pressure. Does this make any difference? If the dynamic pressure ...
1
vote
1answer
331 views

Gas compressed and cooled

If a certain amount of a gas is compressed into a cylinder by the action of a piston that reduces its volume (lets say at a low speed), the kynetic energy of the gas molecules increases, what is ...
-1
votes
0answers
26 views

Books for someone interested in physics/space [duplicate]

As an avid reader of more realistic SF and someone who has always been interested in physics and astrophysics, I was wondering if someone could suggest both some introductory books on the subject, and ...
0
votes
0answers
5 views

What does gravitational lensing equal in time diolation to gravity?

How close does a person need to get in a black hole in orbit to get 2x speed in time and what would that equal in g force?
26
votes
3answers
3k views

What is this shadow being cast upon?

The picture below is from on top of Mt. Shasta at sunrise. The sun was directly behind me when I took the picture and it appears to be casting a shadow on.... the sky itself? Can anyone explain ...
0
votes
0answers
23 views

What is the minimum math level required to comprehend general relativity? [duplicate]

I am currently working on a B.S. In chemistry and only need to go up to Calculus II, though I like to dabble in physics. What other math classes could I take to gain greater understanding of higher ...
0
votes
0answers
7 views

how to get the matrices in partial trace

Good day, I want to ask the matrix that obtained from this link How to take partial trace?. answer from @Nontriviality below In principle what you do is to multiply the square matrix by rectangular ...
0
votes
1answer
115 views

Reduced density matrix

During a course on quantum mechanics we've been talking about density matrices. Now I came across the following exercise. Consider a two spin $\frac{1}{2}$ systems, labeled 1 and 2. Calculate: ...
-1
votes
0answers
19 views

How would you go about solving this graphical mass problem?

I've tried finding the x and y components of the vectors created by each mass to find the resulting vector's magnitude. However, my answer of 0.354 meters keeps getting marked wrong. Any ideas on how ...
1
vote
0answers
35 views

Confusion in Maxwell's derivation of Ampere's Force Law - Part III [on hold]

I am reading Maxwell's "A Treatise on Electricity and Magnetism" and I have some confusion in the following pages: The element ds is resolved into its components $\alpha$ and $\beta$;and the ...
-1
votes
0answers
17 views

How much potential energy stored by a dam?

Considering a dam of height $h$ which holds back a rectangular based reservoir of water with base area $A$. The reservoir contains a mass $m$ of water (up to $h$) of density $\rho$. How much potential ...
0
votes
0answers
10 views

How To Arrive At Ground State Metric of Kaluza-Klein Theory

The ground state metric, after an extra dimension of space is compactified (to a circle) in Einsteinian gravity, is the metric which corresponds to the R_4 × S_1 geometry of the separated dimensions. ...
-1
votes
0answers
21 views

Determination of nature frequency and differential equation of vibration of Hartnell governor?

I found this solution for the nature frequency but here it does not include the Ball weight and centrifugal force in the moment balance equation about the pivot (O), it is wrong answer...is not it? ...
0
votes
3answers
68 views

Significance of wave number?

Till now all I know about the wave number is its formula i.e. ${\frac{2\pi}{\lambda}}$. I always wanted to know what it really means. So can anyone please, explain me its physical significance?
0
votes
0answers
15 views

Is it safe to use the USB ports of a 110v surge protector connected to a 220v socket? [on hold]

During my visit to the US, I have bought a surge protector with USB ports: Monster Power EXP 350 I'd like to know if it is safe to use while connected to a 220V european power socket, using a ...
0
votes
1answer
122 views

On Thermodynamics of Spontaneity of the Reduction-Oxidation Chemical Reactions

According to the first and second law for a closed system containing different chemicals we have \begin{align} &\delta Q - \delta W = dU = T dS - p dV +\sum_i \mu_i d N_i\\ &\Rightarrow\;\...
-2
votes
0answers
32 views

How to start teaching? [on hold]

Twenty years ago I was professor of mathematics and mechanics in Russia. Here, in the USA, I've never had experience in professorship. Today I have maybe a strange idea to try to educate people ...
0
votes
1answer
31 views

Derivation of continuum expression of the first law of thermodynamics

Continuum expression of first law of thermodynamics: $$\frac{D E_t}{D t}=\nabla\cdot({\bf \sigma\cdot v}) - \nabla\cdot{\bf q}$$ (I've seen it in my physics book) How this equation is derived? ...
2
votes
3answers
48 views

Size and density of neutron stars

Most of the books which I looked at give approximately 10 km as the radius of a neutron star. Just yesterday I looked at a book by Dave Goldberg titled The Universe In the Rearview Mirror (2013) which ...
0
votes
0answers
19 views

Antenna measurements and parameters calculation

Lets suppose we have some data collected from antenna measurement. For every theta and phi point in any coordinate system ( here refering to Ludiwg coordinate systems II and III) the data can be ...
1
vote
1answer
19 views

The expression of the density in terms of molecular mass and the distribution function

I am reading a book about the boltzmann equation, the author gives the expression of the fluid density $\rho$ as follows: $$\rho(\mathbf r,t) = \int {M\,f(\mathbf r,\mathbf c,t) \, \mathrm d\mathbf c}$...
7
votes
7answers
1k views

Prove that an electron in a hydrogen atom doesn't emit radiation

According to electrodynamics, accelerating charged particles emit electromagnetic radiation. I'm asking myself if the electron in an hydrogen atom emits such radiation. In How can one describe ...
2
votes
3answers
51 views

Can astronomers observe neutron stars optically?

Are there any neutron stars near enough for astronomers to observe them optically? If not, then how close are we to having the technology to do so?

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