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8th grader knows trig, calc and basics of 9th grade physics .Wants to learn higher physics

I am an 8th grader. I know some basics of physics like the entirety of 9th grade stuff .I know some trig and calc( basics of differentiation + chain rule + integration).I have self learnt vectors too. ...
CODE_FOR_PURSUIT's user avatar
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6 views

Ignore the imaginary part of a solution when numerically integrating

I have the following equation: $$\frac{\pi\cot B}{A}=\int^{\pi}_0\left(\frac{\frac{b\cos x\sin^2B}{R}+\sqrt{-\frac{b^2}{R^2}\sin^2B\sin^2x+sin^2x+cos^2x\sin^2B}}{sin^2x+cos^2xsin^2B}\right)^2\cos xdx$$...
rdemo's user avatar
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0 answers
13 views

Where am i going wrong in this circular motion problem

What am i doing wrong Bob of a pendulum is taken to horizontal position and left. Find the angle of string with vertical when the vertical component of velocity is maximum. The vertical component of ...
Krishnaprasad R's user avatar
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0 answers
14 views

Why is R not the Radius of Curvature, here?

Consider this question, Two masses A and B are connected by a massless string. A rest in equilibrium on a rough horizontal table and limiting friction is acting on it. B hang vertically at a distance ...
PinkAura's user avatar
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0 answers
17 views

Wave packet at $t<0$

If there's wave packet $\psi(x,t)$ in zero potential and $\psi(x,0)$ is given, what happens when $t<0$? I know that for $t>0$ the wave as a group moves at group velocity $\frac{d\omega}{dk}|_{...
Irene's user avatar
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0 answers
21 views

Gravitational Fluctuation [closed]

Is there any possible array of black holes, optimally placed as close as possible but no merger occurs, that could cause gravitational Fluctuation, meaning more gravitational pull on one part of a ...
Mark Swartz's user avatar
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0 answers
30 views

Electrostatic induction with planes [closed]

I'm trying to solve a problem that asks to calculate the final internal and external charges of two conducting, initially neutral, planes (let's call plane $1$ and plane $2$), with a third non-...
meu estudo's user avatar
-1 votes
0 answers
17 views

Heisenberg's equation of motion, commutator of $\pi(\vec x,t)$ and the free Klein-Gordon Hamiltonian

For the free Klein-Gordon field the Hamiltonian is given by: $$H=\int\;d^3x{1\over 2}\bigg(\pi^2(\vec x,t)+(\nabla\phi(\vec x,t))^2+m^2\phi^2(\vec x,t)\bigg),$$ and using Heisenberg's equation of ...
Albertus Magnus's user avatar
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39 views

How to draw topological defect line in LaTeX?

This is somewhat between TeX stackexchange and physics stackexchange. With Latex, it became much more easier to write equations, and with tikz, pictures can be drawn. However, with the introduction of ...
ShoutOutAndCalculate's user avatar
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30 views

What causes impossible colors (supergreen) that can be represented on a gamut to not be visible to the eye?

Supergreen is a color with an RGB value of (0, 255, 0), making it fully green, with no other colors. Now, according to my research, it is impossible for the human eye to detect this color. Doing ...
Astrovis's user avatar
1 vote
2 answers
39 views

Why is the horizon problem a problem?

I am curious about physics and astrophysics in particular, although I have no academic basis. Usually, I find it easy to understand the concepts and explanations, but I have particular difficulty in ...
Alaor's user avatar
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2 answers
77 views

Way to get information from inside black hole to outside?

So imagine a black hole the size of 100 km, and then there is a giant rod that is 50 km and pretends that the rod doesn't get broken due to tidal forces, and also assumes that the rod has a mini-robot ...
MiltonTheMeme's user avatar
0 votes
1 answer
46 views

Why does the curvature change with respect to the sign of the wave function?

In quantum mechanics, in the context of studying unidimensional potentials, we studied this case of potential And to analise the possible looks of the wave function $\phi$, we divided in 3 regions, ...
Ivy's user avatar
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-2 votes
2 answers
70 views

Use of infinity in physics [closed]

There have been lots of questions on this site about the use of infinity in different ways in physics. Infinitely big - Physics near null infinity Infinitesimals - Using differentials in physics ...
mmesser314's user avatar
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22 views

Problem with the calculation of proper time to reach the singularity of Schwarichild B.H [closed]

i'm trying to solve the following exercise: "Consider a free falling observer toward a Schwarzchild black hole along the radial direction. Show that once the observer reaches the horizon he will ...
Daniele Antonucci's user avatar
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0 answers
13 views

Understanding electric conduction in tight binding model

Let's consider a system of free electrons moving in a one dimensional lattice with dispersion $\varepsilon(k) = -2t\cos{ka}$, ($a$ is the lattice spacing and $t$ the hopping amplitude). Let's now ...
Matteo's user avatar
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1 answer
61 views

Why aren’t there any more revolutionary discoveries in science anymore? [closed]

I read John Hogan’s The End of Science book, and while we are making discoveries and improvements in science all the time; we aren’t discovering things on the fundamental level like fire, gravity, ...
Max's user avatar
  • 97
1 vote
1 answer
8 views

Question on fluid jet profile in the limit of zero surface tension

While reading on the Plateau Rayleigh instability of fluid jets, the following thought came to my mind: suppose we have a fluid jet with zero cohesion forces (and therefore zero surface tension) ...
user2554's user avatar
  • 455
2 votes
1 answer
41 views

Why does $S$-matrix theory end up being a covariant formalism when it is not obvious that it is?

A principle of QFT that is frequently invoked, repeated, and potentially subject to rigorous verification is that the theory in question must exhibit Lorentz covariance and be invariant under the ...
Davius's user avatar
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0 votes
2 answers
30 views

The path-independence of work done by an electrostatic field

We know that work done by conservative forces is path-independent and so is work done by electrostatic force but how can we prove it using Coulomb's law? I know such a question has already been asked ...
Ayesha J.'s user avatar
0 votes
1 answer
42 views

Applications of Schrodinger vs Korteweg-de Vries equations

The Korteweg-de Vries (KdV) equations are derived from the time dependent Schrödinger equation. What are the applications of these equations? If I work on solving the KdV equations, to what extend the ...
mle's user avatar
  • 101
0 votes
2 answers
69 views

What particles are described by the Klein-Gordon Equation?

The Klein-Gordon equation $$\left(\frac{\partial ^2}{\partial t^2} - |\nabla|^2 + m^2\right)\phi = 0\tag{1}$$ should describe non interacting particles without spin. So what particles in the standard ...
Noumeno's user avatar
  • 4,336
-2 votes
0 answers
51 views

Why we don't use the magnetic field of coil protons? [closed]

This requires mental imagery. This is a fundamental question about charged particles. First I will give you some data and then I will ask the question. We have an electric machine with a permanent ...
Sobhan 's user avatar
-1 votes
0 answers
47 views

What causes to an object with one fixed point to spin [closed]

In case if an object that have only one fixed cylinder in the middle would, be pused it would spin. But this motion is not explainable by the law of movment of Newtown. Is it microscpic event that ...
daniel's user avatar
  • 147
-1 votes
0 answers
29 views

Peak voltage vs RMS voltage [closed]

I am trying to find a graph that verifies that the gradient from a graph of Vpeak vs Vrms is root 2 (1.414). I have completed an experiment that shows this but I need a second source for my schools ...
Francias dortmund's user avatar
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0 answers
46 views

Method of images vs. Multipole expansion

I've just done an exercise in which I have a charge $q$ in front of 2 grounded conductors, and I have to calculate the potential in the region $x,y>0$. Nonetheless, out of curiosity I've decided to ...
AlanFox86's user avatar
  • 552
-4 votes
1 answer
49 views

Thought experiment: how to define time in a world where no regular movement exists? [closed]

How would we define time if we would live in a world where all movements are chaotic in nature and there would be no repetitive patterns, not in the earth's orbit around the sun, not in the earth's ...
BBroodco's user avatar
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0 answers
14 views

Calculating the proportion of incident energy transferred to kinetic energy in the photoelectric effect

Light of two wavelengths, $λ_1$ and $λ_2$, is incident on a metal surface of work function $ϕ$. If there is an equal number of photons of each wavelength incident per second, what is the maximum ...
Developer's user avatar
0 votes
2 answers
66 views

Instantaneous speed x instantaneous velocity

Related to Distinguish between instantaneous speed and instantaneous velocity I understand that the average velocity is given by the displacement divided by the change in time, and it is a vector ...
Quiet_waters's user avatar
0 votes
1 answer
57 views

Direction of propogation of a EMW [closed]

If let say i have an EMW given by- (Note the difference between $k$ and K) B(x,y,z)=$B_0sin[(x+y)\frac{K}{√2}+wt]\hat k$ i got confused in 2 different outcomes when i wanted to find out the direction ...
Amit Rai's user avatar
  • 143
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0 answers
14 views

Shape of an isochoric curve in T-s and h-s diagrams during phase changes

In the pV diagram an isochoric curve is, of course, a vertical line whereas in the T-s diagram it has the form: $$T(s)=T_0 \space e^{\frac{s-s_0}{c_V}}\tag1$$ so it is an exponential function (steeper ...
User198's user avatar
  • 325
0 votes
0 answers
22 views

Variation of radiation energy with respect to distance from source [closed]

Suppose there is a radiating souce at x=0. Will the energy received per unit time be same at x=0 and x=100? If not then how does it vary?
Curious Gyan's user avatar
-2 votes
1 answer
40 views

If every particle always follows a geodesic, why do we make any sort of differentiation between geodesics and anything else?

Because all particles must follow their geodesics, is there any reason we make a differentiation between a geodesic and a "non-geodesic"? And is there any possible way to get a particle to ...
WestPoint's user avatar
0 votes
0 answers
38 views

Lami's Theorem Problem

Lami's Theorem states that the magnitude of each force in an equilibrium state consisting of three coplanar, concurrent forces acting at a point is directly proportional to the sine of the angle ...
Jeffy James's user avatar
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0 answers
9 views

Can topologically non-trivial edge states exist without an energy gap?

I am relatively new to the field of topological materials, and I came across a paper that claims that they found topologically non-trivial states in a material. Basically, the authors found a type-I ...
Mikhail Petrov's user avatar
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0 answers
29 views

Counting degrees of freedom in theories with two-forms

I am reading Counting the number of propagating degrees of freedom in Lorenz Gauge Electrodynamics. I am thinking that I can apply the same arguments to the case of a two form, whose components are ...
schris38's user avatar
  • 3,918
-1 votes
0 answers
21 views

How do I confirm that solar eclipse glasses block (a substantial fraction of) UV rays and near-IR rays?

Under pressure I placed an order for "solar eclipse glasses". They claim: Conforms to and meets the Transmission Requirements of ISO 12312-2, Filters for Direct Observation of the Sun ...
Sam7919's user avatar
  • 177
1 vote
0 answers
33 views

Gauge redundancy and Gauge fixing

Take any gauge invariant theory, for instance QED. The QED Lagrangian is invariant under $$A_{\mu}(x)\rightarrow A'_{\mu}(x)=A_{\mu}(x)+\partial_{\mu}. \alpha(x)$$ I have chosen a local gauge ...
schris38's user avatar
  • 3,918
0 votes
3 answers
83 views

Can I modify the heat transfer equation by including the volumetric heat capacity in the partial time derivative? [closed]

Consider a porous material in which the pores can be drained or filled with water gradually in time. Thus, the volumetric heat capacity changes with time. Can I write the heat transfer equation ($\dot{...
RTT65's user avatar
  • 11
1 vote
0 answers
15 views

Why do some powders form powder-filled blobs in a liquid?

e.g., why does this happen? (I think in the picture, it's flour mixed with water. I've seen examples of this with many different powders mixed in liquids, usually water.) What has happened at the ...
David C.'s user avatar
  • 403
0 votes
0 answers
51 views

Question according to geodesic equation?

If we consider a congruence of timelike geodesics parameterized by proper time and a vector field $x^a$ with $x^ax_a=-1$, why is $\nabla_b(x^c\nabla_cx_a) = 0$, where $\nabla$ is the covariant ...
Tim2006's user avatar
  • 13
0 votes
0 answers
68 views

Are eigenvalues of slashed covariant derivative real? [closed]

I am trying to demonstrate that the slashed covariant derivative $$ \gamma^\mu D_\mu = \gamma^\mu(\partial_\mu -iA_\mu) $$ has real eigenvalues: $$ \gamma^\mu D_\mu \varphi_m(x)=\lambda_m \varphi_m(x)...
Gorga's user avatar
  • 65
1 vote
1 answer
351 views

How do magic mirrors work?

I recently found out about the magic mirror. Both sides of the mirror look the same, and it appears to be dark, if looked at closely, like sunglasses (but lighter in colour) but looks like a normal ...
Stuti's user avatar
  • 618
1 vote
0 answers
43 views

Why is the Ramond vacuum a Majorana fermion in type II string theory?

I understand that in order to have a supersymmetric spectrum in string theory, the vacuum has to be a MW (Majorana-Weyl) spinor under $SO(1,9)$. But I don't see where the Majorana condition on the R ...
Ballanzor's user avatar
  • 490
1 vote
1 answer
41 views

Derivation of Magnetic Energy and Ohm's Law

I am currently reading section 10.1 of Classical Electricity and Magnetism by Panofsky and came across their derivation for magnetic energy stored in current systems. Consider a process in which a ...
Init's user avatar
  • 31
1 vote
0 answers
18 views

Forms of interaction between two spins

I am learning the principles of nuclear magnetic resonance, and came across the interaction between two Hydrogen nuclear spins, which affects the relaxation properties of materials like water in NMR. ...
night cat's user avatar
1 vote
1 answer
42 views

View distance as a function of elevation of observer

I'm currently reading Jules Verne's Mysterious Island and the author, through his engineer character, keeps repeating the statement that if he climbs up to the top of a mountain to a height of 2500 ft ...
stelevan's user avatar
0 votes
0 answers
6 views

Input Parameter Location for 3x3 Beam Trace Matrix for Misaligned Optical System

I'm trying to use a 3x3 beam transfer matrix from "Generalized Beam Matrices: Gaussian Beam Propagation in Misaligned Complex Optical Systems" by Anthony A. Tovar and Lee W. Casperson https:...
JoeMama's user avatar
1 vote
0 answers
38 views

How did the author get these three expressions? [closed]

I am reading Nonplanar Relativistic Flow by Peter G. Eltgroth, Phys. Fluids 15, 2140–2144 (1972) doi. I do not understand how the author arrives at expressions (12), (13) and (14) at page 2. Equation (...
mattiav27's user avatar
  • 1,305
0 votes
0 answers
37 views

Evaluation of Wilson loop in double-slit experiment [closed]

I am confused about eq. 24 of this paper. The authors claim that in the limit $\omega T \gg 1$, $$\oint _{u-l} dt e^{-i \omega t} \vec{v}(t) = \frac{i}{\omega}(\vec{v}_1-\vec{v}'_1-\vec{v}_2+\vec{v}'...
Andrea P.'s user avatar

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