0
votes
1answer
48 views

Plateau–Rayleigh instability for liquids with low $Re$ number

I'm working on a project about Plateau–Rayleigh instability for liquids. But I've a question. we can examine the fluids with high $Re$ number that the influence of viscosity is negligible, but what ...
2
votes
1answer
105 views

Understanding rocket equations [closed]

I'm doing a science project where I have to explain the physics behind a trip to an exoplanet and I also have to explain about rocket equations while doing so. I know that a trip to an exoplanet is ...
1
vote
1answer
63 views

Rotational equilibrium Paradox

A block of mass M and height h is moving on a rough surface of coifficent of friction 0.5 .The block is moving with a velocity v at some instant. if we balance the torque due to frictional force and ...
0
votes
0answers
22 views

How atmospheric pressure affects liquid but not solid? [duplicate]

The barometer indicates a difference in elevation of liquid mercury level due to the effect of atmospheric pressure. For 1 square cm of surface the atmospheric pressure exerts what is equivalent to ...
1
vote
1answer
78 views

Physical interpretation of the constant coefficient appearing in solution to the Schrodinger equation

The product solution to the Schrodinger's equation is $$\Psi_{n} \left ( x,t \right )=\psi\left ( x \right )\phi\left ( t \right )$$ By superposition, the solution becomes $$\Psi \left ( x,t \...
0
votes
0answers
47 views

Deriving Maxwell's equation from the Lagrangian of an electromagnetic field with a charge density $\rho$

I want to derive Maxwell's equation from the Lagrangian of an electromagnetic field with a charge density of $\rho$ The Lagrangian is given by $$L={1\over2}(\epsilon_0E^2-{1\over\mu}B^2)-\rho\phi+\...
0
votes
1answer
89 views

Angular momentum of a rigid body about any points

Is angular momentum about all points same if the body is rigid and is rotating/translating/rolling with a constant velocity? Why? No external force is acting on the body.
1
vote
1answer
53 views

Difference of water pressure

We know that $P = \rho gh$, so is it true that water pressure at 2nd floor will be higher than water pressure at 9th floor of a 12 story building?
1
vote
2answers
52 views

What is the purpose of the directions for vector quantities such as angular velocity and torque?

Looking at just both angular velocity and torque, many other exhibit this same property. What is the purpose of and usefulness of having a direction that is in the Z-direction? (assuming that, in the ...
1
vote
1answer
79 views

At a fixed inital velocity, What throwing angle will give the projectile the most trajectory length? [closed]

This is a diagram of a projectile motion: Given a constant initial velocity, What angle gives the most trajectory length? By length I mean the length of the parabola from the point the ball is shot ...
0
votes
0answers
42 views

What is the probabililty that a fair coin lands on its side?

This is a popular gag in movies, but I wonder how likely it really is. What is the probability that a uniform cylindrical coin (with radius $1$ and height $h$) lands on its side? If the ground were ...
0
votes
3answers
144 views

What is physical significance of energy?

John Rennie said, actually all particles are basically energy in the sense that they were created by adding energy to a quantum field. This applies whether you're creating a photon, an ...
4
votes
1answer
82 views

Is it a law of physics that all machines will break?

The question sounds kinda dumb when I say it out loud but at the same time I'm very curious. When things break, is it solely due to an intrinsic design flaw or is it due to entropy? And is the ...
0
votes
1answer
23 views

Changing angular momentum with no forces to do torque

Suppose a particle of mass $m$ moves in a straight line at velocity $v$ some distance away from an axis, as shown here at times t1 and t2 (where the axis of rotation is located at the origin of the ...
2
votes
0answers
33 views

How fast does water have to be moving for it to gain a lot of heat? [duplicate]

A random question popped into my head a few minutes ago: objects, when moving fast enough, start to get resistance from the air. Since there is friction between the air and the object [water], there ...
2
votes
2answers
439 views

Why does the pressure of fluid increase when the diameter of the pipe increases?

Assuming mass flow rate doesn't change and it's a closed system. Why does going from a smaller pipe to a large pipe cause an increase in pressure? What is the kinetic energy converted to as the ...
0
votes
1answer
34 views

Data for Tully-Fisher Relation

I have a derivation of the Tully-Fisher Relation and I'd like to test it against some real data. Does anyone know of a catalog where I can find the maximum velocity ($V_{flat}$) and radius (of $V_{...
-3
votes
1answer
104 views

Which gives the most realistic pictures, Mirror, camera or their combination? [closed]

By googling, I have found several different opinions about how to take one's own facial images more realistically: Some said photos taken by cameras (smartphone's cameras, if specific) are more ...
-1
votes
3answers
66 views

how can you tell if liquids have different densities [closed]

help me i need an answer asap for finals
5
votes
1answer
104 views

Why quantum fluctuation existed before big bang?

I read somewhere that quantum fluctuation can give rise to a big bang and thus the creation of a universe which we know today, where do these quantum fluctuations come from if space is only created ...
1
vote
4answers
49 views

How do I figure out the totally airborne height for a given machine?

Technically "airborne" can just mean to move through the air, but I would like to know how high you have to be before you are entirely supported by air in a helicopter-like machine, as opposed to ...
0
votes
0answers
26 views

Is it possible to determine perigee distance from distance recordings from a spacecraft to Earth?

If you are on a spacecraft orbiting earth in an elliptical orbit and were able to take measurements of the distance between the spacecraft and earth as well as the time intervals between those ...
3
votes
1answer
63 views

Why Conserved Current Should Not Need Renormalization?

May be this is trivial but I need to understand why the renormalization of conserved current is not necessary ? As for example, in this paper, they demand (2$^{nd}$ paragraph of the 2$^{nd}$ column in ...
0
votes
1answer
89 views

How to proceed (Tough Problem) [closed]

The problem that I am considering is to find the shortest path (or geodesic) on a surface with the equation $z=f(x,y)$. The path is parameterized by $s$ so that the path goes from $(x(0)$,$y(0)$,$z(0))...
6
votes
1answer
159 views

Is there mechanical strain on a wire along the direction of current flow?

The (attractive) magnetic force on two parallel wires can be seen by the two wires bending towards each other. This can be explained by the Lorentz force acting on the charges and the charges "pulling"...
0
votes
0answers
46 views

Center of mass of a quantum field

In classical field theory the Noether conserved quantities associated to the translation symmetry are the momentum of the field $P^i = \int\! d^3 x\ T^{0i}$, where $T^{\mu \nu}$ is the energy-momentum ...
0
votes
1answer
58 views

Why not run a cable from the north pole to the south pole to access its energy (magnetic or electrical)

Would a cable tied to the North Pole around the curve of earth downwards to the South Pole give us access to a HUGE AMOUNT of energy (magnetic or electrical) by linking into it.
1
vote
1answer
38 views

Experiment to show $a \propto F$

I learnt about an experiment to show that acceleration is proportional to force. It was done by placing a trolley (like a toy car) on a smooth track. At the end of the smooth horizontal track was a ...
-4
votes
1answer
127 views

do we live in 3.5 dimension? [closed]

After watching interstellar movie i came to know that time is 4th dimension and watch some videos and read articles which says there is there is around 10 dimension(11 also). As x,y,z are 3 dimension ...
0
votes
1answer
56 views

How force is transmitted in Magnetic field (Quantum mechanically )

According to particle physics , every fundamental force has its force carrier particle. Photon is a force carrier particle of electromagnetic force but What is the process through which magnetic ...
0
votes
0answers
45 views

Doubt in Path integral equation

In Pokorski's "Gauge Field Theories" book, page 108 we find equation (2.87) $$\int{}\mathcal{D}\phi{}e^{iS_0[\phi]+iS_I[\phi]+i\int{}d^4y\,\phi(y)J(y)}=e^{iS_I[-i\frac{\delta}{\delta{}J(x)}]}\int{}\...
1
vote
2answers
57 views

What are the limitations of recording very faint sounds?

Is it possible to record very faint sounds like, say, the bending of a strand of hair? Part of the problem, I imagine, would be the need to find a way to isolate the target sound from other sounds. ...
0
votes
1answer
60 views

Liquid phase is a highly compressed gaseous phase

$\mathbf{Q:}$ While teaching "Real Gases", my professor remarked last day that "Liquid phase is a highly compressed gaseous phase." But he did not explain the reason behind it and left it as food for ...
0
votes
1answer
80 views

How to find potential energy per unit volume of a simple harmonic wave in a string?

How to derive the formula for potential energy per unit volume of a simple harmonic wave in a string? My book just states the formula as $\frac{1}{2} \rho v^2 (\frac{dy}{dx})^2$ without the proof. $\...
0
votes
1answer
35 views

Radiation weighting factor photons

I'm wondering about the equivalent dose and the radiation weighting factor of photons (according to ICRP 103). Why is the weighting factor independent from the energy of the photons?
0
votes
1answer
60 views

I want to make something but i have to bend light without a black hole

I am trying to make something that requires a vortex of light, but the only thing i know that can do that is a black hole . . . so is there any possibility that i can make the vortex without a black ...
0
votes
0answers
27 views

Excited states of atoms [duplicate]

I have a few basic questions about excited states of atoms. Are excited states intrinsically unstable, and do the atoms naturally and always return to their ground state unless they continue receiving ...
1
vote
0answers
37 views

To delimit and isolate a quantic system ? A pure fiction ? Or not?

An unreliable author wrote : "parameters that define uniquely the result of each trial and trial in an experiment. For instance, assume that we work with the polarization singlet. The power of ...
0
votes
1answer
49 views

How do you find the time dependent equation of motion here? [closed]

Find the position of a mass $m$ rotating in a vertical circle at the end of a string length $\ell$ in a uniform gravitational field, for any value of time $t$, given initial position and velocity. ...
1
vote
0answers
86 views

QFT and lack of rigour [duplicate]

How can physicists compute path integrals and such if there is no rigorous definition of it? If they can get an definite answer, there must be some method they used, so what is meant when ...
0
votes
0answers
49 views

Radiative corrections and stability

What is meant by the terms radiatively stable and radiatively unstable? I know that when calculating physical observables in quantum field theory, such as the mass of the electron, to obtain a more ...
3
votes
4answers
107 views

Why the word “measurement” all the time?

I'm trying to learn more about the properties of light. In all the youtube videos and related to the two-slit experiment, the explanations always say that "measuring" can change the outcome. Why do ...
0
votes
2answers
98 views

Barometer barometric pressue

the barometric pressure and height on earth are 10^5 pa and 760 mm respectively . Then what is barometric height if it is taken at moom . I think at moon the gravity will decrease then pressure ...
1
vote
2answers
124 views

Laser cooling of atoms: more area or more power?

I want to optimise a Magneto-Optical trap. Laser beams come from the the x, y and z directions (positive and negative) and slow the atoms down. Would it be better to increase the beam spot-size (...
0
votes
1answer
77 views

Rate of flow of water fluid mechanics

If we have a cylindrical tank of area $A$ which has a small outlet of area $a$ at the bottom of the surface . And the container starts filling with a constant rate $k [m^3/sec]$ . Now the max. level ...
-1
votes
1answer
103 views

Alternative Explanation of Quantum Double Slit Experiment with Different Polarizing Filter Over Each Slit

I recall reading that if you put a parallel polarizing filter over one slit and a perpendicularly polarizing filter over the other slit, and send a singe photon to the slits, then the two waves that ...
0
votes
0answers
30 views

How to understand the simplified tight-binding representation on square lattice?

I have read a paper in this website:http://cmt.nbi.ku.dk/student_projects/bsc/Haider_Moradi_BSc_thesis.pdf I am curious about how to understand the simplified tight-binding representation on square ...
0
votes
3answers
100 views

Flow of electrons in an open circuit

In a closed circuit, electrons flow from negative electrode to positive electrode. In an open circuit, electrons only flow up to the end of the circuit. Why don't the electrons keep flowing into the ...
-1
votes
3answers
292 views

If mass is not conserved but instead energy is conserved, is it right to say that the fundamental particles are photons? [closed]

If mass is not conserved but instead energy is conserved, so is it right to say that the fundamental particle of the Universe is photon instead of protons, neutrons, electrons, leptons, etc and all ...
1
vote
2answers
51 views

Error propagation without analytical expression

I have an algorithm $f$ that takes two inputs $x,y$ and gives one output. I say algorithm because I don't have the analytical expression for $f(x,y)$ (it's a black box in a computer, surely a ...

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