0
votes
0answers
4 views

Physical Nature of the electric field of the current in a circuit

As most of us know that the electric current in a conductor is due to free electrons moving in the conduction band of metallic conductors. What makes then move ? An electric field of course. Today my ...
0
votes
0answers
8 views

Successor to Copenhagen Interpretation as Orthodox Interpreation of Quantum Mechanics

First, I read the questions FAQ for this and I hope this does not violate the rules. I am not asking for personal opinion, but for observations of hard evidence of trends on this subject. When I ...
0
votes
0answers
4 views

Question about the Blandford–Znajek process

I've been trying to understand the Blandford–Znajek process which explains how Gamma Ray Bursts form, but it's still not clear to me how it works. In this article [ ...
0
votes
1answer
11 views

What is the Benefit of Plotting a Log of Net Force vs. Log of Acceleration Graph?

In preparation for a quiz, I've been going over a set of sample questions. One question in particular asks that if I am to graph the logarithm of the horizontal net force of a system vs the logarithm ...
0
votes
0answers
8 views

event horizon vs apparent horizon ramifications

If the event horizon doesn’t exist in the 2-dimension or 3-dimension time-space - and it doesn’t exist if it can’t be measured or observed - then an apparent horizon would be necessary to reconstruct ...
0
votes
1answer
11 views

How do BCDs work?

I get that having more air decreases density and increases buoyancy. However, we can take the diver-BCD-oxygen-tank to be a single system. How can the pumping of air from the tank into a vest around ...
0
votes
1answer
7 views

How do we determine the pressure at the surface of a star?

Is there any means to do so? I know there are some means to determine the surface temperature.
0
votes
2answers
15 views

Free falling object with air resistance, what's the velocity as a function of time?

So, I'm looking into how velocity can be represented as a function of time when the air resistance is also function of velocity. The force of drag is $$ F_d = C||\vec{v}||\vec{v} $$ where $C$ is an ...
2
votes
0answers
25 views

Are there any open questions in physics that a layman can analyze? [on hold]

In math, there are questions like "Is this a knot or not?" which can't fundamentally be solved and simply take a lot of trial and error for an answer. This means that a layman can enter the field ...
0
votes
1answer
13 views

Can we determine the surface temperature of stars other than the sun by using the black body radiation theory?

It is well known that the surface temperature of the sun can be determined by fitting the solar spectrum to the black body radiation spectrum. Is this scheme feasible for other stars? Possibly the ...
0
votes
0answers
9 views

Why does a dynamical gauge field accompany fractionalisation?

I'm trying to understand fractionalisation, of which spin-charge separation is an example. I've read that this is accomplished by introducing a Lagrange multiplier field, which becomes a dynamical ...
0
votes
1answer
16 views

Calculating stopping distance of a car on a slope

I'm having trouble setting up a homework problem properly. We are given the following: A given car can brake to a stop from a speed of 60.0 mi/h in a distance of 123 ft on a level roadway. What ...
1
vote
1answer
49 views

Can a particle have an imaginary mass?

Now, I'm not very involved in the physical sciences, beyond some high-school classes - though I did listen to some college lectures for physics. I was reading "Do Tachyons Exist?" by John Baez, which ...
0
votes
0answers
17 views

Scattering in Black Holes

Let's take your favorite Black Hole and consider the scattering problem for a scalar field around it. Suppose that the Klein-Gordon equation can be separated in the radial and the angular part. Which ...
0
votes
1answer
20 views

Degenerate perturbation theory

I don't understand the part about turning off the perturbation. What is meant by or what is he referring to when he says "upper" and "lower" states. Why must the "upper" state reduce to a ...
0
votes
1answer
18 views

What do I need to calculate UV intensity?

I have a mineralogical UV lamp that I want to use for some research, I only know it's wavelengths. To calculate the µJ/cm3, what else is needed? Distance, time, wattage? Is the value I'm looking for, ...
0
votes
1answer
56 views

Which non-Copenhagen interpretations of Quantum Mechanics have actually produced something useful?

The question has most of it in the name. "Useful" may be interpreted as: measurably different from Copenhagen interpretation and true potentially measurably different and potentially true (i.e. not ...
0
votes
1answer
10 views

Dependance of diffusion coefficient on size?

What's the dependance of the diffusion coefficient on size? More explicitly, suppose I have a particles of characteristic length $l$, dissolved in a liquid. How does $D$, the diffusion coefficient of ...
-3
votes
5answers
51 views

Could it be possible for man to create a star?

If it were possible for us to create a star or a new sun, how could it be done, or how would it have to be done?
0
votes
0answers
26 views

Acceleration of an bubble under the sea

An air bubble arises from the bottom of the sea. Find its acceleration if resistance force is proportional to $\rho Av$ where $\rho$ is density of water, $A$ is cross section area and $v$ is velocity ...
0
votes
1answer
39 views

Navier Stokes : what about angular momentum?

I play with CFD for a while, and suddenly, a transcendantal question raises: :-) Navier Stokes is basically Newton applied on a continuum in Eulerian. For solids, we would consider linear, but also ...
0
votes
2answers
39 views

Is the energy of a collision of two photons the same as one photon hitting a 'wall'?

Special relativity says that the speed of ligt is always the same. So when a photon meets another photon he will encouter it with the speed of light and also the other one. But in case of a wall, the ...
-6
votes
0answers
16 views

The following model describes a jet travelling at 40000 ft at Mach 8. My question is: where do these numbers c0me from?

This model describes flight of an aircraft at 40,000 ft at a speed of Mach 0.8. x˙ = Ax + Bu Matrix A = [-0.0558 -0.9968 0.0802 0.0415 0.598 -0.115 -0.0318 0 -3.05 0.388 ...
-2
votes
0answers
24 views

Motion question [on hold]

I have been struggling to understand how to do this question so some guidance would be great. A racing car of mass 941kg accelerates from 28km/h to 102km/h over a distance of 297m. Frictional forces ...
-1
votes
0answers
14 views

How to find frequency from wave equation [on hold]

I have wave equation for vibrating string with damping $M\ddot{x}+C\dot{x}+Kx=0.$ I used this formulae for finding (natural)frequency $\sqrt{\frac{K}{M}-(\frac{C}{2M})^2},$ is it ok?
1
vote
0answers
21 views

Does a potential of interaction produce also torque?

I have a system of particles (spheres with masses and radii), with $6$ degree of freedom (they are free to move and rotate as they wish). Between each couple there is an interaction potential $V(d)$, ...
1
vote
0answers
15 views

solar energy on a specific location

How to find the amount of solar wattage in any specific place on earh in a monthly manner? by solar wattage I mean the energy recieved from the sun in a squared meters.
0
votes
2answers
27 views

How can space strech a wave?

Because of the expanding of the universe a wave from a far galaxy or star can be streched to more red. But how is space doing that? There must be a kind of 'entanglement' between the wave and space. ...
1
vote
0answers
13 views

Energy and power in a travelling sinusoidal wave

This stuff is driving me crazy. Here: http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/AnalyzingWaves.htm I found that the average kinetic energy per unit length is: $$ \frac{1}{4}\mu ...
-1
votes
0answers
15 views

Problem in statics [on hold]

This is a problem I've been trying to solve for the past days without success. I tried the mathematics forum, since the whole problem consists in finding the value $\beta$ which produces a maximum $P$ ...
0
votes
2answers
23 views

volume of the air bubble in the water

How does the depth affect the volume (the radius) of an air bubble in the water, if the temperature and density of the water are constant. Is there any relation combining this? Can I say that ...
0
votes
0answers
11 views

photometric redshifts - the origin of 1 / (1+ zspec) in photometric accuracy

i have a training sample of sources with known spectroscopic redshifts ($z_{\rm spec}$) and i run a photometric fitting code that uses a template to determine the photometric redshifts ($z_{\rm ...
0
votes
0answers
14 views

complex waveforms

just wondering if anyone can help me out with a expression I need to find out the phase angle of any hardmonic components present ( relative to the fundamental) of this expression v= 100SIN (100 V = ...
2
votes
1answer
19 views

What information does kinetic energy and work give us about a body?

When I studied momentum I learned that momentum says about a body how hard is it to stop it. In addition, I learned that impulse tells us in some way how much time would I need to stop the object. If ...
0
votes
0answers
9 views

How to calculate apex angle of sun shining on the Earth

I'm trying to compare the brightness of various LEDs to the average brightness of natural daylight. LEDs are rated in terms of candelas whereas the Sun is measured in terms of lumens, so I need to ...
0
votes
0answers
9 views

Is the magnetic dipole moment in charged particles the more survivable property than the electric charge?

After asking about Which of the properties of particles are intrinsic properties and why? it was commented "Charge, spin, lepton number, baryon number definitely. Mass maybe." and "is magnetic dipole ...
14
votes
10answers
685 views

Why does hot air raise in a column instead of cold air pressing down?

Ok, this looks like a dumb question or even near trolling, but I really don't understand it. When air is heated over an oven plate, it rises. Obviously, I can check by blowing some smoke in. The ...
1
vote
1answer
15 views

Applicable force at constant velocity

For a body moving at a constant velocity, the force $F_{net}=ma$ Since acceleration is 0, $F_{net}=0$ (i.e force applied = resisting force) Since force applied and resisting force are equal, will ...
0
votes
0answers
21 views

Electric Filed on a point on a sphere

I really want to understand the concept of those problems. Thanks.
0
votes
0answers
13 views

How does back reflection damage optical cavity?

I have a basic question.How does back reflection damage optical cavity?please help me.
2
votes
0answers
8 views

Why is this result wrong for finding speed of a neutron in relation to deBroglie wavelength [duplicate]

So given a deBroglie wavelength 1.8nm and the equations E=hf and E=1/2mv^2 you can get v = 2h/m*(1.8*10^-9) but this is 2 times the expected value. Wherever I look online people use the momentum p ...
2
votes
1answer
46 views

How is LIGO so sensitive? [duplicate]

My understanding is that interferometers can detect distance changes on the order of the wavelength of light being used. LIGO uses 808 nm light but has a sensitivity of 10^-18 m. Where do those 11 ...
1
vote
1answer
20 views

What does ''population'' mean in regards to the excited and ground states of an atom?

I have a problem I'm working on. It seems simple enough, but there is a term I'm not familiar with. It asks for the ''relative populations of the first excited and the ground states for helium gas in ...
1
vote
0answers
13 views

Connected Rods Mechanics

Consider three homogeneous rods, each of mass $m$, length $2l$ and moment of inertia $I$, connected by friction free joints at $B$ and $C$. The rods and joints are all moving without friction on a ...
-1
votes
0answers
10 views

Hele-Shaw Flow/Hele-Shaw Cell Approximation

In the literature of microfluidics, the Hele-Shaw Flow/Hele-Shaw Cell Approximation appears often. Can someone briefly explain its origins and the related references for further reading? Thank you.
1
vote
0answers
11 views

thermal fatigue and thermal conductivity

Today I argued that heating and cooling a metal many times will affect its thermal conductivity. My idea is that heating and cooling, ie. thermal fatigue, will affect longterm the the microstructure ...
2
votes
1answer
31 views

Extrinsic Curvature of Surface of Codimension > 1

We can define the extrinsic curvature of a codimension-one surface as $$K_{ab} = q_a^{\phantom{a}c} q_b^{\phantom{b}d} \nabla_c n_d,$$ where $n^d$ is the normal vector to the hypersurface and ...
5
votes
1answer
61 views

Meaning of integral signs in classical physics

When I began studying physics, by myself, on a universitary textbook, F.J. Keller, W.E. Gettys , M.J. Skove, Physics, about one year ago, I believed that all the integrals that I was going to find in ...
0
votes
0answers
21 views

Reattachment of differential equation in Physics

The following differential equation: $$xf'(x) + f(x) = 2x$$ Has solutions on the intervals $]-∞;0[$ and $]0;+∞[$ : $$f(x) = x + a/x$$ $$f(x) = x + b/x$$ I obtained the only common to the two ...
1
vote
0answers
13 views

Need some help in finding Poynting vector

I am asked to Calculate the Poynting vector of the transmitted wave but I am not sure how. I am able to show the electric field of the transmitted wave as shown above in the picture.

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