All Questions

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baryon acoustic oscillation

I have one question about baryon acoustic oscillation. I understand why we should have the baryon-photon fluid sound wave before recombination: Suppose we have a spherical overdense region. This ...
153 views

in Newtons 3rd law, where does the second body get its energy to react?

A very basic question, and apologies if I have overlooked something obvious. In newtons 3rd law, presumably energy is transfered to the second body from the first body (which itself was subject to an ...
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Gear ratio in bicycles using rotational motion

When we change the gears of the bicycle we are riding, we change the the disc we are currently at (which are located at the place where we pedal) to some other disc. This means the radius of the ...
51 views

Why is moment of inertia for a point same as a ring

The moment of inertia of a point and ring are both $m R^2$. It is interesting that the formula for moment of inertia is exactly the same for both. Is there any physical reason why this is the case? I ...
114 views

Asymmetry in magnetic field direction of an electric wire

The simplest magnetic field is that of an infinitely long wire with uniform current. It does enjoy radial symmetry about the wire and has the variation as 1/r. To find the direction of the resulting ...
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Any textbook about non-renormalizability of gravity?

I have learned general relativity in a graduate-level. My knowledge about QFT is very rudimentary. But, I need to learn about non-renormalizability of gravity. I have these questions. Is there any ...
396 views

Is it possible to surpass the diffraction limit for telescopes?

Telescopes have angular diffraction limit depending on the observed wavelength and aperture diameter. I've read that it's possible to go beyond the limit for microscopes. But is it possible to do the ...
90 views

Charge conjugation matrix in baryon current

In his paper Calculation of baryon masses in quantum chromodynamics (ScienceDirect), B.L. Ioffe considers currents describing baryons. In equation (13) he gives an interpolating current for the isobar ...
221 views

Using sinusoids to represent sound waves

Having some free time, I've begun a mini-project attempting to understand how music works in more detail, which has so far only involved music theory and a bit of set theory. I'm now trying to get my ...
142 views

Isn't the aether existent?

Before you say I'm wrong consider this, Einstein is supposedly the first person to get completely get rid of the various aether models that were proposed. But didn't Einstein actually prove them right ...
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Why does light travels in all directions? [on hold]

My understanding of time, gravity and speed of light: Earth revolves around the Sun. Sun revolves around Milky Way centre. Milky Way also keeps moving. All these movements are caused by gravity. ...
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What happens when you pass a current through a coil made of a ferromagnetic substance?

I know when you pass a current through a length of copper coil or a solenoid, there is the induction of a magnetic flux. But what of the coil made of the ferromagnetic material, the permanent type ...
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Material with incredibly small young's modulus [on hold]

I'm looking for a material with a Young's modulus of less than 100 Pa. I've looked at elastomers, but I haven't had any luck. Thanks for your help, I appreciate it.
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Can everything be described without anything needing to actually “bend”?

Is space bending because gravity actually causes small particles to move differently? If large source of gravity is somewhere are particles extending towards it, creating a "bend" in space? So "bend" ...
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Waves interfere in angle equation

If we had two waves perpendicular to each other, with equations: $x=αsin(ωt)$ (1) $y=βsin(ωt+π/2) ==> y=βcos(ωt)$(2) $sin(ωt)^2+cos(ωt)^2=x^2/α^2+y^2/β^2=1$ $x^2/α^2+y^2/β^2=1$ is an equation ...
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Why is a sine wave considered the fundamental building block of any signal? Why not some other function?

It is mathematically possible to express a given signal as a sum of functions other than sines and cosines. With that in mind, why does signal processing always revolve around breaking down the signal ...
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Find the total energy stored in the network at the time of steady state? [on hold]

Find the total energy stored in this network at the time of steady state.
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Is Dark Energy and or Dark Matter directly proportional to EMR? [on hold]

Is Dark Energy directly proportional to Electromagnetic radiation (EM radiation or EMR)?
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What is the significance of being equivalent up to local isometry?

Background : I am reading the paper device independent outlook on quantum mechanics. The author mentions the concept of two pure states being equivalent up local isometry. From what I understood two ...
150 views

error propagation with an integral

My question here is about how to determine the error of an integral given individual uncertainties in two parameters defining the function being integrated. I used a curve fitting function to ...
23 views

Three blocks on inclined plane problem [on hold]

I came across this problem on physicsgalaxy.com. My approach: Found limiting friction between 30 kg and 50 kg as 72 N. Found limiting friction between 50 kg and 40 kg as 256 N. Now P+50 sin(37) ...
331 views

How did we disprove aether wind?

We know that the universe is not vacuum. The average temperature of the universe is 3° above absolute zero. So some "aether" really exists, but that is not some gas with very low density, but ...
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Detecting molecules in space?

http://www.forbes.com/sites/alexknapp/2012/02/24/nasa-detects-solid-buckyballs-in-space/ I refer to the above article, which mentions that buckyballs "far smaller than the width of a hair" were ...
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Traveling near the speed of light? [duplicate]

Suppose we can travel on a spacecraft near the speed of light, how long it would take for the person on the spacecraft to travel one light year, not to a person observing him/her from Earth, if there ...
22 views

Work Function Calculation with Local Electrostatic Potential

On the Wikipedia site, it describes the work function equation as W = -e\phi - Ef, where phi is the electrostatic potential of a vacuum nearby the surface of the material. So my question is, how can I ...
521 views

How can a fruit be used as a battery cell?

Fresh fruits can be used as batteries for glowing bulbs, but how this is possible? I mean how can electric charges flow through fruits? Do they contain chemicals like cells?
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What kind of orbit would be needed to map the surface of a nonrotating planet?

I am not a mathematician and it may even take me weeks to understand the math involved but I have an odd question on orbital mechanics that I hope will be worth the experts' time. I am a hobbyist ...
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Vibrating water container problem

I am struggling with visualising and understanding the phrasing of this question - cross posted from Math stack exchange since this forum is more appropriate: "A water-filled container is ...
309 views

Fluid Mechanics with calculus on manifolds

Fluid Mechanics is a branch of physics that uses a lot of vector calculus in $\mathbb{R}^3$ to describe phenomena mathematically. Calculus on manifolds, however, is the straightforward generalization ...
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Why isn't there a limit for a Euclidean rotation, as for a Minkowski rotation?

From invariance of the Minkowski scalar product, we get the Lorentz transformations. In addition, we get a constant $c$ preventing space-like and time-like intervals being rotated into one another. ...
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can any one please explain in simple terms phase change of reflected light

Phase change is used to explain interference in thin films . The concept is not explained there . Does the change in direction by 180 mean phase change ?
2k views

Software for physics calculations

What is some good free software for doing physics calculations? I'm mainly interested in symbolic computation (something like Mathematica, but free).
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Induced EMF of a rectangular loop should be zero?

Considering the shape of a rectangular loop in a changing magnetic field: The induced $\epsilon$ would be zero? Since a rectangular loop is a combination of wires in series to create such a shape. ...
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How does rotational energy transfer to linear energy?

So I have recently started looking into moments of inertia, and all that stuff. I have come to a question which has a plane inclined at some angle theta and a sphere at the peak. The G.P.E at the top ...
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Prove that Laughlin's 3-electron states are a complete set of states

In R. B. Laughlin's 1983 Physical Review B article, Quantized motion of three two-dimensional electrons in a strong magnetic field, Laughlin separates out the center of mass motion of the electrons, ...
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spooky nonlocal communication, or bad abstract?

I'm referring to this recent paper, "Experimental Proof of Nonlocal Wavefunction Collapse for a Single Particle Using Homodyne Measurements" by Fuwa et al. published in Nature Communications. ...
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Velocity change of air down a cone?

Does the velocity of fluids(specifically gasses) change when traveling down a cone from the wide opening to the narrow opening? If so, is there an equation used to calculate the acceleration or ...
1k views

Eliminating IR light reflection perceived by a steep viewing angle

I am having a problem with reflection on an acrylic surface, in the IR part of the spectrum. This reflection is interfering with an algorithm that looks at objects, as it makes two show up when only ...
299 views

Rigid body problem in 2d

I have some questions about this exercise: In an horizontal plane, a $OA$ bar with mass $m$ and length $a$ moves, with another bar $AB$ (same mass, double length) attached in the point A. In the ...
139 views

What is the angular distance between Ptolemaic perigees of Mercury?

In his excellent treatment of the history of the science of astronomical distances and sizes, Albert van Helden says (p.29) that The complicated [Ptolemaic] model of Mercury has the curious ...
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“If the astronaut found that light slowed down relative to his motion, he would have detected the very ether wind that Michelson failed to detect”?

The following extract is from Relativity Simply Explained by Martin Gardner (Amazon link): Consider an astronaut in a spaceship that is racing alongside a light beam. The ship is traveling with ...
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How to get the magnetic field strength in space near a solenoid

I am trying to find the magnetic field strength along the axis of a solenoid. If I know the strength of the field at the center of the solenoid, and I know the distance from the center of the ...
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Eddy currents Vs. Inducing EMF in opposing the change?

In the following circuit there is a power supply applying a voltage(+$V$) to a circuit with resistance ($R$), current($I$) is now flowing in the circuit, and there is a movable part like so: The ...
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The Riemannian Curvature in Deformations

Is there a direct correlation between the Riemannian Curvature tensor and the deformation gradient tensor in continuum mechanics?
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Will the gravitational pull of air affect the falling rate of an object?

After looking at this question: Don't heavier objects actually fall faster because they exert their own gravity? A thought occurred to me that due to the increased gravitational pull of the ...
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Do the eigenstates of the Pauli operators correspond to the six directions of the 3D world?

I understand that the six eigenstates of the three Pauli operators $X, Y, Z$ correspond to the six poles of the Bloch sphere. By fixing an orthonormal basis of our physical word, does "measuring Pauli ...
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When to use lateral magnification vs angular magnification?

What is the essential difference between lateral and angular magnification (like why do we need to use both and when do we use which)? Also, is there a relationship between the two magnifications?
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How to solve bound states of 2D finite rectangular square well?

I want to solve bound states (in fact only base state is needed) of time-independent Schrodinger equation with a 2D finite rectangular square well V(x,y)=\cases{0,&\$ |x|\le a ...