# All Questions

147 views

### Effective masses for different direction

Assume we have an indirect semiconductor where the effective mass becomes anisotropic in different directions. Usually, one talks about a mass in parallel and perpendicular direction referring to ...
15 views

### Charge density on two hemispheres, enclosing a conducting sphere

Two uniformly charged non conducting hemispherical shells each having uniform charge density $\sigma$ and radius $R$ form a complete sphere (not stuck together) and surround a concentric spherical ...
13 views

### triboelectric effect at a liquid-liquid boundary?

In reading up on the triboelectric effect, most experiments deal with solid-solid interfaces. I've found some studies regarding solid-liquid boundaries, and even some engineering manuals outlining the ...
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### Specific heat capacity for Adiabatic process

We can define infinite number of specific heat capacities between two temperatures(e.g $c_p ,c_v$) . Could we do that for an adiabatic process. As for adiabatic process heat addition or removal is ...
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### A puzzler in induction and special relativity

Some reading I was doing jogged my memory about a puzzle in E&M that hit me back in my undergrad days, but I just let it go at the time and never found an answer. A pretty common undergrad E&...
767 views

### Is running in a zigzag helpful in avoiding being shot by an arrow? [on hold]

Two people A and B start at a certain point. B runs away from A to another point. A shoots arrows at B. Is it helpful for A to run in a zigzag rather than in a constant direction? To be more ...
187 views

### General motion of a cone on an inclined surface

Suppose that a solid cone is placed horizontally on an inclined surface and is initially at rest. How will the cone move when it starts motion due to its weight? I know that its motion depends on the ...
59 views

### How is one element capable of radiating (almost) every wavelength? [duplicate]

Black bodies are considered as emitting all wavelengths. A incandescent light bulb has (nearly/almost) also the continuous blackbody spectrum near-perfect color rendition. In this bulb is only one ...
47 views

### Moving of spin up and spin down electrons in a magnetic field

Suppose we have an electron in a conducting space, and now we apply a magnetic field. Now according to the right hand rule, the electron will have a circular motion in the plane perpendicular to the ...
44 views

### Why do we integrate in the following derivation? [on hold]

Electric potential due to a point charge. Let a point O have charge $q$ at a distance $x$ from point A and at a distance $r$ from point P ($r<x$). Suppose a test charge $q_1$ is placed at A force ...
26 views

### Can we see interference if move screen? [on hold]

In interference using electrons in double slit experiment, we cannot use light source, as it disturbs apparatus. But, can't we simply move screen towards and away from screen, to know where they ...
1k views

### What does the Schrodinger Equation really mean?

I understand that the Schrodinger equation is actually a principle that cannot be proven. But can someone give a plausible foundation for it and give it some physical meaning/interpretation. I guess I'...
35 views

### Is this possible to create a 1D or 2D thing in real?

We are living in the fourth dimension(time).So we can now travel through the third dimension. Now just imagine to make a 1 dimension thing, A line in real world. If I draw a line in paper with a ...
58 views

### Details of Newtonian Prediction for Mercury's Precession

Could anyone point me to a book or outline the methods used to actually calculate the 532 arcseconds per century that Newtonian theory apparently predicts for Mercury's precession. I am completely ...
111 views

### Capacitor/Inductor Resonance

I am struggling to understand the concept on resonance in electric circuits. I understand that a inductor builds up a charge on it, then the current flows to the capacitor, charging it. But then ...
43 views

### What is a magnetic line of force?

Do magnetic limes of force 'flow'? If so, what is it that is flowing? What is the 'line of force' composed of?
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### Uncertainty principle-QM [duplicate]

I some trouble understanding the uncertainty principle. I understand most of the math derivation but not the physics. Is there any intuitive explanation of this idea, and why is the uncertanty does ...
64 views

### (1+1)-General Relativity

Goodevening everyone, my question is: What is the interest of studying the (1+1)dimension General Relativity? Can you explain please? Thank's in advance!
63 views

### Flame shape and size(length) depending on gravity

How would the shape and size of a flame(from a simple candle for example) depends on the gravity? Suppose all the relevant information is known, like candle dimensions and its chemical composition, ...
18 views

### Does resonator will always dampen the driving oscillator?

I was doing a question about resonance of sound box connecting to a tuning fork. It asks why the sound lasts for a shorter time with sound box than if the tuning fork is struck identically without the ...
50 views

### Such a huge mass for Higgs boson? And how can it, as a quantum, decay?

With a mass of 126GeV/c2 Higgs boson would have a mass slightly greater than a caesium atom. Isn't it too much? Wouldn't be in this way the ubiquitous Higgs field so dense to cause problems for the ...
38 views

### Great Void negative gravity [on hold]

According Integrated Sachs–Wolfe effect on light, Great Void should have relatively negative gravity - it just push mater out, and maybe even light. What is cosmic speed hypothetical spaceship should ...
243 views

### Dielectric boundary

I am trying to determine why electric field may be confined to a certain region if there is a large difference in the permitivity for example if electric field flows through water and then reaches a ...
25 views

### Can orbiting a black hole 99.99% speed of light make other object with relatively fast clock travel faster than light, relative to me?

If i orbit a black hole, 99.9% speed of light, time for me is moving slowly, relative to me, planet earth is aging fast, and i have traveled 10 years into the future(relatively) in 1 second, suppose ...
19 views

### Derivation of differential governing equation of Hartnell governor? [on hold]

I tried to derive the differential governing equation using energy conservative method and newton's second law, but I came up with very large and complex equations, even with assumption of small angle ...
48 views

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### How small can a sample size be of space to detect space-time curvature?

What is the minimal sample size of space necessary to detect space-time curvature?
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In chapter 6.2 of Weinberg's QFT Vol.1, he gave the general form of Wick contractions of all possible fields(scalar, spinor, vector, etc.), he showed $$\Delta_{lm}(x,y)=\theta(x-y)P^{(L)}_{lm}\left(-... 3answers 2k views ### Gravitational force when standing on an infinite disc If a person were to stand on a flat disc of thickness 1 meter but infinite diameter, would they experience finite or infinite downward force? There is an infinite amount of mass, all of which ... 1answer 11 views ### Nuclear physics study materials I'm currently a ChemE undergraduate student and wish to pursue masters in nuclear engineering. Can you suggest some introductory reading material so that I can get acquainted with nuclear engineering ... 2answers 82 views ### Hologram without requirement of screens I'm not much familiar with holograms and I've read a few articles on how holograms are made. I have a question that how does hologram get projected in air? If it were tyndall effect, then we could see ... 0answers 37 views ### Speed of sound in solid — temperature dependence Let v denote the speed of sound in a fixed solid, at a fixed temperature T. This will depend on properties of the solid (such as the bulk modulus and density). Given an increase in T, does v ... 2answers 355 views ### Bernoulli's equation and pressure in a (mostly) sealed container Let's say that I have a large soda bottle. I drill a small hole through the side of it, put my finger over it to seal the hole, and fill the bottle up with water. When I let go of the hole, water ... 2answers 56 views ### How much mass must Earth lose to lose its Moon? Maybe I am wrong about the basic concept here, but for my curiosity: how much mass would need to leave the Earth (like satellites and rockets) to create an imbalance between the Earth and Moon so that ... 1answer 39 views ### Why don't windows and mirrors cancel light? So I understand that when light goes from a material of low index to a material of higher index it picks up a phase change of 180. Most glass has an index of around 1.5. I know that when light goes ... 1answer 43 views ### Even when the drift velocity of the electrons is very small, how is current in the circuit established immediately? So I have this question in my textbook and Ive also got it in my test. Ive written a wrong answer. My friend wrote the drift velocities of each particle add up and he got full marks. Is it right? Can ... 0answers 28 views ### Problem in thermodynamics [on hold] There is a 500 watt heater and a ton of wood. How much will the temperature of the wood increase over the course of 6 hours? P = 500 W m = 1000 kg t = 6 h = 21600 s c_wood= 1700 J/kg E = P * t ... 0answers 49 views ### Plotting a Function [on hold] I have the following result:$$ n_z(t) = 1 - 8 \sum_{k = 0}^{\infty} |g_{k}|^{2} \frac{\sin^2 \Big (\frac{(w_k - w_{0})t}{2} \Big)}{(w_k - w_{0})^2} $$I want to figure out the dependence ... 3answers 42 views ### Two qubits system in polar co-ordinates I know that I can write a single qubit state in terms of polar co-ordinates (r,\theta,\phi) on a Bloch sphere. \rho = \begin{pmatrix} \frac{1+r \cos\theta}{2} &\frac{r \exp(-i\... 1answer 31 views ### Calculate how much air will cool from an amount of ice? [closed] So, there are 3kg of ice at -18 degrees Celsius and 50kg of air at 30 degrees Celsius. I need to calculate how much the air will cool by the time the ice reaches its temperature. I thought I ... 2answers 79 views ### Why do we restrict to electric field when describing light? Why do we restrict only to electric field when describing light as electromagnetic wave? I mean from Maxwell equations we can derive wave equation for electric field and also for magnetic field but ... 1answer 54 views ### A fan is connected to a pipe, what happens to the airflow after the pressure drop? Overview I am trying to find out what happens to the air flow within a pipe if a fan cannot generate the required pressure to overcome the friction within the pipe. After much research I am aware ... 2answers 2k views ### Pauli matrices as measurement operators I am trying to understand a paper on the Bell test experiments. I understand that if we wanted to measure the spin of a spin-1/2 particle in state \psi along the z-axis we would apply the operator ... 1answer 110 views ### Thermodynamics - mass of gas expelled Question: An open vessel contains 200 mg of air at 17 degrees Celsius. What percentage of weight of air would be expelled if the vessel is heated to 117 degrees Celsius if the pressure is to ... 0answers 19 views ### How rigorous is the description of the edge of the Kitaev Honeycomb as a CFT? My understanding of the Kitaev honeycomb model is that high-level abstract properties (anyons and their braid statistics) can be seen to emerge the microscopics of the model (fermions and vortices). ... 1answer 63 views ### Unit Vector vs. Basis Vector When reading about vectors I sometimes have seen unit vectors multiplied by the components and other times I've seen basis vectors used instead.$$v=x \hat i+y \hat j+z \hat kv=xe_x+ye_y+ze_z ...
I need Isospin calculations to predict the relative amount of strong decays, namely $D^{**0}\to D\pi\pi$, where the $D$ and $\pi$ can be charged or neutral. My problem is the order of contracting the ...