# All Questions

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### Ratio of Stagnation to Normal Flow Properties in Incompressible Flows

I know in compressible flows the ratio of stagnation to normal flow variables is a function of the Mach number and usually the specific heat ratio. Does this ratio mean anything for incompressible ...
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### how to count such a huge number of oscillation in atomic clock

can someone help me out please?/ actually a second is defined as time taken for 9,192,631,770 oscillations of ceasium hyperfine levels...but its not exactly that the electron moves up and down between ...
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### What is r-r' in spherical polar coordinate and cylinderical coordinate?

I am into solving Vector equations in Physics like Electric field and Magnetic field. $$E=\frac{1}{4\pi\varepsilon_0} \int\frac{\rho(r')\hat{\mathcal{R}}}{\mathcal{R}^2}d\tau'$$ ...
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### Does changing a closed surface in the manner outlined contradict Gauss' Law?

As I understand it, Gauss' Law states that the electric flux on any arbitrary closed surface is equivalent to the sum of all charges enclosed within the surface times a constant. Mathematically, this ...
3k views

### Does a charged particle accelerating in a gravitational field radiate?

A charged particle undergoing an acceleration radiates photons. Let's consider a charge in a freely falling frame of reference. In such a frame, the local gravitational field is necessarily zero, ...
490 views

### Determining flexural modulus by performing 3 point bending test using hollow cylindrical tube

I would like to decide the flexural modulus of the material of plastic tube by performing 3 point bending test according to the ASTM D 790 procedure. In ASTM D 790, the form of the specimen is ...
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### Resistance of a washer with square cross sectional area

Consider a resistor in the shape of a washer with resistivity $\rho$. It has a square cross sectional area $A$ and inner radius $a$ and outer radius $2a$. Find the resistance across the two wires like ...
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### Can the question of a gravitationally accelerated charge radiation be tested experimentally?

I know that the question of radiation from a gravitationally accelerated charge has been discussed extensively at Does a charged particle accelerating in a gravitational field radiate?. Yet the ...
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### Electric flux of a charged rod through a uniform disc

), I have an assignment regarding electric flux. The question I was given has the following sketch: The first question was about the force on the rod from the disc at the Z axis. I reached the ...
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### Pendulum acceleration vector [on hold]

I'll make this quick, I want the acceleration vector for a pendulum WITHOUT using angle acceleration and angle velocity, just using the tension and gravity forces.
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### Why can´t we call the energy released after the annihilation of a particle and its antiparticle pure energy? [on hold]

As a particle and its antiparticle annihilate each other a huge amount of energy is released, and no mass is left. This energy always comes in the form of force mediating particles (photons, gluons). ...
52 views

### QFT Weinberg scattering thoery

I have a question about beginning of chapter 3 (scattering) of QFT.vol.1 by Weinberg I think (am I wrong?) $\Psi_\alpha$ means a collection of particles each with a definite $p^\mu$ specially $p^0$ ...
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### Derivation of Einstein's relation in Drift Diffusion model for Semiconductors

I'm currently reading Semiconductor Devices: Basic Principles by Jasprit Singh. In this book he gives a derivation of the Einstein relation for the Drift Diffusion model of semiconductors, supposing ...
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### Rocket launch from a mountain

If we were to build a high speed rail up the side of a mountain like in some Science Fiction movies, what is the velocity needed at the point of leaving the mountain excluding angular momentum from ...
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### How thin lens model work when there are two images with different distances from the lens?

I am trying to understand how thin lens camera work. From what I understand of thins lens model, the image is formed on image plane that obey the equation $$\frac1S_1 + \frac1S_2 = \frac1f$$ So ...
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### Energy required to accelerate from different reference frames

So I've recently been studying relativity a lot trying to understand it and I feel like I grasp most things conceptually but I have one issue I've been trying to understand for the last couple days ...
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### Flame composition types

Can anyone define the atomic structure of a carbon fuelled flame. I have studied variations of flame patterns but this type seems to stand out.
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### Higgs mechanism in quantum GLSM

My question is regarding the following Gauged Linear Sigma Model (GLSM) in two dimensions. $$\tag{1} S=\int d^2x\Big(-D_{\mu}\overline{\phi} D^{\mu}\phi +\frac{D^2}{2e'^2} +D(|\phi|^2-r)\Big).$$ ...