0
votes
0answers
7 views

Density and Wave Speed

For a string, the formula for wave speed is $v=\sqrt{\frac{T}{\mu}}$, where $\mu=\frac{m}{L}$. The greater the linear density, the more massive the string is per unit length, the more inertia it has, ...
0
votes
0answers
9 views

Directional derivative of the Ricci scalar in the direction of a Killing vector field

Do I need the Levi-Civita connection for the directional derivative in the direction of a Killing vector field of there curvature scalar to be 0?
0
votes
0answers
9 views

What is the time dilation effect in the presence of two equal and opposite gravity sources?

If one were between two equal and opposite gravity sources, would the time dilation effect cancel out, since the acceleration is cancelled out?
1
vote
0answers
12 views

Electric field operator in 2D geomatry

In the free field (3D), transverse electric field operator is given by the below expression; $$e^{\bot}(\textbf{R}) =i \sum_{\textbf{p},\lambda}\Big( \frac{\hbar cp}{2V\epsilon_{0}}\Big)^{1/2} ...
0
votes
0answers
8 views

Dynamic response of temperature change when identical fluids flowing mix together

As shown in the below figure , there is a mixing of a fuel in a system. the mass flow rates m1,m2 are different, the pipe diameters are all equal but are different in length.I need to get the ...
3
votes
0answers
26 views

What is special about quantum entanglement? [duplicate]

Get two pieces of paper. In secret write the same number on both papers. Transfer one paper to the Moon. Look to the paper which is left at the Earth. Voila! We know what is on the Moon paper. The ...
-7
votes
0answers
17 views

what health per-captions should be taken for theoretical senerios [on hold]

so been working on some detail research and i been having some trouble since have of the experiment affects are still only theoretical but let me explain as best i can. so lately i been working with a ...
-1
votes
0answers
16 views

What is the difference between cosmological horizon and event horizon?

Do the terms cosmological horizon and event horizon mean the same thing?
1
vote
1answer
71 views

Is Wikipedia's definition of angular velocity incorrect?

According to Wikipedia, the general formula for the angular velocity of a particle in three dimensions is $$\boldsymbol \omega = \frac{\mathbf r \times \mathbf v}{\left |\mathbf r\right|^2}.$$ But if ...
0
votes
0answers
28 views

What does $(I + iδH^t)(I-iδH)$ equal to? [on hold]

$I$ is equal to 1, $δ$ is a small change. According to 43:04-43:10 of this video http://theoreticalminimum.com/courses/quantum-mechanics/2012/winter/lecture-4 \begin{align} \ i{ δ }(H^t-H)=0 ...
-1
votes
0answers
18 views

Proof of transformation between contravariant and covariant components of vector [on hold]

What is the proof of the relation ${g^{ir}g_{rj}=\delta^i_{j}}$ where ${g}$ is the metric tensor and ${\delta}$ is the Kronecker delta. EDIT:The operations is known as equivalent to raising and ...
-3
votes
3answers
33 views

Can't we consider that EmDrive is Pushing against Space itself?

When something move through space it pushes against something else in space with equal force. However, EmDrive warps space around. So can't we say it's pushing against space itself, and thus momentum ...
0
votes
1answer
19 views

Find the separation distance for a line of oil being squashed between two flat plates

I was wondering if someone could give me some help on how to start this problem, I'm really struggling to get my head around it. A long line of oil is being squashed between two flat plates of length ...
2
votes
1answer
107 views

Would the hot windows break? [on hold]

I have a question that I was thinking about for a long time. I live in Kuwait and in the summer season the weather reach 50°C which is extremely hot specially inside a car. What if I was able to ...
-1
votes
0answers
11 views

chemical thermodynamic [on hold]

Calculate U and H for each of the following changes in state of 2.50 mol of a perfect monatomic gas with CV,m 1.5R for all temperatures: (a) (1.50 atm, 400 K) → (3.00 atm, 600 K); (b) (2.50 atm, 20.0 ...
1
vote
1answer
13 views

Expression for spontaneous emission in solids

I have yet to find a reliable source for the expression of the rate of spontaneous emission in a solid. Can anyone confirm if the following is correct? The basic ingredients of the calculation are ...
0
votes
1answer
28 views

Do wormholes violate causality [duplicate]

Does opening and closign a wormhole to send a message within seconds across the galaxy violate causality? Wouldn't different observers disagree about the order of events and what effected what? Is ...
1
vote
1answer
38 views

Different electrons, why aren't they all the same?

Why do we say that there are different kinds of electrons when discussing different situations in physics? For instance the Weyl electron, Dirac electron etc. From my exceedingly basic knowledge isn't ...
0
votes
1answer
52 views

M-theory and Mathematics

If the framework of M-theory is the right path for a unification of gravity with quantum mechanics, is it obligatory to believe that, at a certain level, reality is not just easily describable by ...
0
votes
0answers
36 views

Hydrogen is the ONLY Element?

Let's say you have Hydrogen and it's isotopes, Can you fuse them together to create all the 118 elements, by fusion or something else, Can anyone give me any research paper or anything which gives ...
1
vote
1answer
40 views

Completeness relations of eigenstates in the Heisenberg picture

I've been reading Srednicki's introduction to path integrals and I'm slightly unsure of the notation that he uses for the completeness relation of position eigenstates in the Heisenberg picture. In ...
-1
votes
0answers
5 views

Magnetic field lines for perpendicular current carrying wires [on hold]

Given two straight current carrying conductors, carrying the same current I kept perpendicular to each other. What would the magnetic field lines look like?
-3
votes
0answers
17 views

if you feel that a wire is warm,what will you check or do? [on hold]

pls,answer ASAP homework to be passed the other day
0
votes
0answers
10 views

Is Earth's magnetic field moving? [on hold]

Is the Earth's magnetic field moving? Why is the Earth's magnetic field said to be moving?
-1
votes
1answer
17 views

Maximum horizontal speed and vertical speed interdependently

I need to limit hspeed and vspeed taking direction in count, I know how to calculate the maximum speed as a whole, but not limiting that speed by setting the hspeed and the vspeed
0
votes
1answer
18 views

Do you know any graphing software for graphing equipotential lines?

well, do you know any software for graphing equipotential lines? I only know how to graph straight lines :( Thanks for any information.
4
votes
0answers
15 views

Concerning topology of BPS states of the the M5-brane

My question is about the M5-brane in M-theory. I would like to know whether the BPS states of the M5-brane worldvolume theory (especially the 1/2 BPS and 1/4 BPS ones) are independent of the topology ...
0
votes
0answers
11 views

Opposing EMF's, in an odd arrangement…?

A conductor has two separate uniform magnetic fields $B_1$ & $B_2$: The magnetic fields both changing at the same rate over the same duration of time, inducing an EMF($\epsilon$) on each part ...
0
votes
0answers
6 views

How to determine limiting load of a motor which uses separate Over Load Protection Component

I am using an dual voltage electric motor of 1.5Hp and RPM of 1750.Dual voltage motor works on 110Vac and 230Vac but with `single 60Hz frequency. There is no over load protection built-in on the ...
0
votes
0answers
9 views

What is the difference between Rashba coupling effect and spin orbit coupling effect

We know standard spin-orbit coupling and spin Hall effect. But what is the differences in Rashba coupling effect? What changes in Rashba coupling effect?
1
vote
1answer
32 views

Oscillation of Atom

What exactly does it mean when one says 'one atom of Caesium 137 oscillates 9,192,631,770 times'? I do understand the general thing about oscillation but what exactly is the oscillation of atom, what ...
0
votes
0answers
10 views

Do two magnets lose magnetism when they are kept apart forcibly with a small gap separating them from being attracted?

I know that two magnets with same poles kept near each other lose their magnetism. Is it true if they are kept near each other with the opposite poles (without letting them contact each other)?
0
votes
2answers
34 views

Gravitational force acting on two particles

According to Newton's Laws of Gravitation, $F=Gm_1 m_2/r^2$ So gravitational force F is directly proportional to $1/r^2$. Now if we consider 2 point masses in vacuum at rest at a distance 'd' ...
5
votes
2answers
213 views

When/why does the principle of least action plus boundary conditions not uniquely specify a path?

A few months ago I was telling high school students about Fermat's principle. You can use it to show that light reflects off a surface at equal angles. To set it up, you put in boundary conditions, ...
1
vote
0answers
31 views

Why is a relativistic quantum theory of a finite number of particles impossible?

In Dyson's book Advanced Quantum Mechanics , he said "These two examples (the discovery of antimatter and meson) are special cases of the general principle, which is the basic success of the ...
0
votes
0answers
18 views

Which one is laser threshold condition

From one side For two mirror laser we say that the minimum round trip steady state requirement for the threshold of lasing is that the gain exactly equall the loss.in this case the intensity of beam ...
0
votes
1answer
34 views

De Broglie's Matter wave equation dividing by zero

I was just thinking about De Broglie's matter wave equation: $\lambda=\frac{h}{p}$ where $p$ is the momentum of the object. But what if the object is at rest? Won't we be dividing by zero? What if we ...
0
votes
1answer
22 views

Where Does the Energy Come From in this Example?

I can't figure out where the energy comes from for the work in a video I found about how the pyramids could have been made. (I do not have enough rep to post the link of it as well as the picture but ...
0
votes
1answer
42 views

Why can black hole evaporate if objects need infinity time to reach event horizon?

I am new to black hole, but have a question about it: Object needs infinity time to reach event horizons (by observer) Particle-antiparticles separates, one of them drops into black holes to cause ...
-1
votes
0answers
18 views

Can somebody derive the answer to the below statics question? [on hold]

Can somebody derive the answer to the below problem ?
-1
votes
1answer
15 views

Stress( Mechanics) [on hold]

The diagram represents a steel tube with wall thickness $w$ which is small in comparison the diameter of the tube. The tube is under tension, caused by a force $T$, parallel to the axis of the ...
0
votes
0answers
18 views

Dynamic coefficient of friction

Is there any way or equation or table to find dynamice coefficient of friction between Aluminum and asbestos or steel with asbestos in wear test at various temperature,pressure and velocity ?...
0
votes
0answers
15 views

What is Black Hole Information Paradox?

I read here, when something falls on black hole its physical information is lost and it's physical state is dissolved. But didn't the Hawking say that the mass that falls on black hole is escapes out ...
2
votes
1answer
29 views

Shouldn't dark matter distort light and there for be directly detectable?

It is an established fact that gravity bends space time and therefore distorts light. We know that Dark matter acts gravitationally. So, just for giggles, lets say I had a sphere of dark matter ...
-1
votes
0answers
12 views

Can hydrogen be used for superconducters

Okay so i learned that heaver isotopes of a substance have a lower superconductivity transition temperature. Does this mean that things like hydrogen which are lighter can be used for high temperature ...
0
votes
1answer
31 views

Physically, what causes joint pain?

I wasn't sure if there was a better site to post on with regards to this- I wasn't sure if people on the physical fitness stackexchange would give a sufficiently mechanical description. When ...
1
vote
0answers
28 views

On resonance of an RLC circuit

How do I prove that the width of resonance in an RLC circuit is the inverse of the proper time of the circuit? I know that the amplitude of charge in the condensator is ...
0
votes
1answer
41 views

An impossible relationship between variables

This book chapter defines $CV$ as follows: $$ CV^2 = 2\pi\nu^2\int^\frac{V_{th}-V_{ss}}{\sigma_V}_\frac{V_{r}-V_{ss}}{\sigma_V}dxe^{x^2}\int^x_{-\inf}dye^{y^2}(1 + erf(y)) $$ However, Figure 15.2 in ...
0
votes
2answers
31 views

Temperature rise during friction

Why the temperature increase when the load increase during friction ? Why the temperature increase when the contract time increase during friction?
1
vote
1answer
13 views

What the effect of thermal diffusivity on temperature rise during friction

If we have two material in friction wich metal will produce the temperature?the metal with lower diffusivity or with higher diffusivity will be the source of temperature

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