# All Questions

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### Given an equation of an elliptical orbit, is it possible to find satellite´s speed at a certain point?

As the heading says: given an equation of an elliptical orbit, is it possible to find satellite´s speed at a certain point? I'm playing a bit with simulations of planets and satellites in the solar ...
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### What are the prerequisites needed to grasp analytical mechanics? [duplicate]

What are the mathematical prerequisites needed to grasp analytical mechanics conceptually and technically? What textbook is adequate for this purpose for an undergraduate student? To understand the ...
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### General procedure for determining whether the choice of origin is arbitrary [on hold]

Please give a general procedure for determining whether the choice of origin is arbitrary, or give relevant references (if not in general, then if possible for elastodynamic scattering in Cartesian ...
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### How to relate acceleration to time [on hold]

Edit I do not understand how asking for the formula of the acceleration of gravity can be considered homework or even off-topic on a physics site. I had added an introduction with some figures to ...
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### What is Colour-Colour-Intensity Diagram?

What are color-color intensity diagrams? These are 3D plots usually used in high energy astrophysics ( particularly in relation to XRBs).
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### Causality and response functions

Referring to David Tong's notes on Electromagnetism, page 29 (of the PDF, numbered 183), section 7.5.4; It is proved that the frequency domain response function (in this case describing the ...
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### Rotation, Boosts and their relation to Spin

Angular momenta are the generators of rotations. For example, $L_1,L_2,L_3$ represents the orbital angular momentum operators which represents rotations in 3-D space in $xy$, $yz$, $zx$ plane. Spin ...
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### What is the importance of $2d$ supersymmetric gauge theory? [on hold]

I have been working $2d$ $N=(2,2)$ theories focused on checking duality like, Seiberg duality (2d version: named "Hori-Tong" duality) and its extension. During the study i got $2d$ $N=(2,2)$ ...
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### The Earth's gravitational magnetics [on hold]

The Earth has magnetic properties correct, so can they be measured and if so what are some consistencies?☆
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### Quantum field operators in HEP and CMT

For a real scalar field (which is a bosonic field) we have these commutation relations : $$\left[\phi(x,t),\phi(y,t)\right]=0 \qquad \qquad \left[\phi(x,t),\pi(y,t)\right]=\delta(x-y).\tag{1}$$ But ...
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### Why do statistical ensembles always fix three variables?

In basic course in statistical (classical) mechanics and thermodynamics, the ensembles used (microcanonical, canonical, grandcanonical, NPT) always assume exactly three variables (n,V,T in canonical ...
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### What is the physical significance of Rapidity in Relativistic kinematics?

Recently I have came across a new term called rapidity in relativistic kinematics. We are using it in relativistic kinematics due to its additivity whereas velocity is not a additive quantity in ...
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### specific heat of water and ice

We know that denser objects have lower specific heat capacity. Since water is more dense than ice, water must have lower specific heat capacity than ice but we know that water's heat capacity is ...
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### Final velocity and instantaneous acceleration of an object on an inclined surface [on hold]

An object with 4.0kg mass is on a frictionless inclined surface with 30 degree incline. The object travels the distance of 15m in 3 seconds. What is the final speed of the object and the instanteous ...
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### Why does water reflect light?

Why does water reflect light? What is actually happening when light is reflected by water? We know why metals reflect light; water, however, is not metal, but it still reflects light and we can see ...
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### Derivative of the action integral [on hold]

I need to find the partial derivative of the action $S$ with respect to the generalized coordinate $q(t_f)$ and according to my textbook, it should equal the generalized momentum $p(t_f)$. I ...
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### Weight handling capacity of motors [on hold]

I am a student of final year electronics engineering at University of Pune. Our project is PLC based sweet manufacturing machine. In this device, we are using a mould which will be approximately 1 kg. ...
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### Why time of flight remains same for a projectile even though collision takes place?

Why time of flight remains same for a projectile even though collision takes place ? Suppose a ball is projected with some velocity V with some angle θ the the time of flight is T. Now if another ...
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### Units of Velocity Components and Metric Tensor Components

I was watching a GR lecture on youtube, and the speaker explains that the units of the components of velocity are $[v^{\alpha}]=\frac{1}{T}$, the metric tensor has units $[g_{\alpha\beta}]=L^2$, and ...
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### Odd physics question I thought up the other day [on hold]

pi(being 3.1415) divided by the square root of the speed of light multiplied by mc2( or 200 metric tons- if that helps).....Just curious. THX. Tried to google it, but it couldn't answer it. I think of ...
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### Proof of reflected and refracted waves being in the same plane as that of the incident wave and its projection on a planar interface

Please give a proof of reflected and refracted waves being in the same plane as that of the incident wave and its projection on an ideal planar interface between two linear, homogeneous, isotropic, ...
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### Electronic energy level in alpha and beta radioactivity

My textbook says that : " When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom changes for alpha and beta radioactovity but not for gamma radioactovity. " ...
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### why charges reside on the surface on conductor? [duplicate]

In a hollow conductor and in a spherical shell the charges reside on its surface and there is no electric field inside it. What is the reason for both phenomena?
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### Is quantum physics truly random or does it just appear that way because of Heisenberg uncertainty principle

The behavior of an electron (and other tiny things) is said to be probabilistic because we can't say where an election will be when we measure it, but only where it will probably be. As I understand ...
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### Hollow Iron pipe electromagnet? [on hold]

How strong would a electromagnet be if I use a hollow Iron pipe as the core? The thickness of the pipe will be 2-3 cm. How much weaker would this electromagnet be compared to a non-hollow ...
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### Hamiltonian density for Proca Lagrangian [on hold]

The (classical) Proca Lagrangian density for a massive vector field $A_\mu$ is $${\cal L} = -\frac{1}{4} F_{\mu\nu} F^{\mu\nu}+\frac{1}{2}m^2 A_{\mu}A^{\mu},$$ where as usual ...
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### Torque when net external force is zero

I was studying force couple and my teacher said that in this the torque about any point is same. That led me to wonder if in any case if net external force is zero then is torque about any point in ...
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### What does not have mass and can not absorb light? [on hold]

invariant mass anyone agree? Should this term be called something different because a proton in this state has no mass at all.
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### Contradiction in a simple torque/rotation problem - two ways of calculating external force don't agree

Suppose we have a rigid system of two point objects (both of unit mass) connected with a massless rod, with the objects horizontal on the x axis, at a distance $r_1$ and $r_2$ from the origin, ...
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### Classical - quantum analogy of Berry phase

I am reading this webpage about Berry phase: http://materia.fisica.unimi.it/manini/berryphase.html I am happily convinced about the first "elementary geometry" example they provide. Now I am trying ...
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### Nuclear to Electricity Energy Conversion

Currently nuclear power generates heat, which heats water into steam that turns conventional turbines. The energy conversion is as follows: photonic->heat->kinetic->electric This would result in low ...
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### Describing 3-slit interference patterns

I'm typing up some physics notes about wave interference patterns and want to include a graph of the wave produced by a 3-slit experiment: Does anyone know what formula produces this kind of curve? ...
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### Minimum mass of a stuff to orbit you? [on hold]

How little does an object have to weigh to orbit you in space?
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### Popular books on cutting-edge physics [on hold]

I watched this video, in which different types of topics are discussed like Quantum Information, Quantum Computation, Universe as hologram, Hidden information, Quantum Entanglement, Black holes and ...
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### Motion Basic Physics Question [on hold]

An object is released from rest and falls a distance $H$ during the first second of time. How far will it fall during the next second of time? (in terms of $H$) It is assumed the only force acting on ...
I was doing some reading on the Michelson-Morley Experiment. One of the principle equations for the equations is this one. $$\frac { 2w }{ c } \times \frac { 1 }{ 1-\frac { { v }^{ 2 } }{ { c }^{ 2 ... 0answers 11 views ### Calculating half-life in a delta-function potential model for radioactivity Consider a model for radioactivity in which a 1D particle of mass m and energy E is confined between two potential barriers: V(x) = \alpha (\delta(x) + \delta(x-a)). Define and calculate the ... 2answers 49 views ### Kinetic energy and work confusion [on hold] I know that \frac{1}{2}mv^2 is derived from W = \int \vec F \cdot\ d\vec s, but are there exceptions to the kinetic energy formula? Newton says that unless an external force is applied, a body ... 2answers 347 views ### Can pressure exist without a container? I always hear pressure defined as the force exerted by particles on the walls of the container they're being held in. This makes sense since the mathematical definition of pressure is  p = ... 1answer 66 views ### Lagrangian in rotating reference frame I have a homework question I am working on, and I'm stuck on the last term in this proof. The problem states: Question: Consider a primed set of axes coincident in origin with an inertial set of axes ... 2answers 21 views ### Exercise pulleys and accelerations [on hold] The system shown has ideal massless pulleys and no friction. The pulleys 1 and 2 are fixed and the pulley 3 is mobile. The mass m2 is rigidly attached to the center of the pulley 3 by a support ... 0answers 49 views ### Michio Kaku's lightsaber [on hold] I have just watched Kaku's video about a light saber. He presented something he called a light saber. But honestly, would you call that thing a light saber? I would call it a plasma torch. As far as ... 1answer 15 views ### Gravitational PE lost v Elastic PE gained in mass - spring If a spring has a load m added to it (and so is extended by x), the gravitational potential energy lost by the mass will be mgx. The elastic potential energy gained by the spring is ... 3answers 701 views ### What really is a Dirac delta function? Yesterday a friend asked me what a Dirac delta function really is. I tried to explain it but eventually confused myself. It seems that a Dirac delta is defined as a function that satisfies these ... 0answers 5 views ### What determines the Bloch wavepacket length scale? We know in the semiclassical Boltzmann theory, there are several length scales: the lattice constant a, the Bloch wavepacket spread \xi, other length scales such as the mean free path l, the ... 0answers 34 views ### Could there be ways to form hypergiant stars, quasars or supermassive black holes at the beginning of the Dark Ages? Original title: Heat loss in collapsing parcels of gas or weak plasma at the beginning (not the end) of the cosmological dark ages Star formation from collapsing parcels of primordial gas in the late ... 1answer 24 views ### Photon gas, recovering state function from empirical result Given that for a photon gas the following is true:$$U=3pV\mu=0$$I want to recover a state function U(S,V,N) (or S(U,V,N) or F(T,V,N) etc.) in the most direct, simple way. So far I got ... 1answer 39 views ### Would the detection of advanced waves be possible in curved space-time? In the transactional interpretation of quantum mechanics reference 1, inspired by the Wheeler–Feynman absorber theory, a transaction is formed between the emitter and absorber by a superposition of ... 2answers 90 views ### Why is the Spin of the photon neglected? We know photons have spin s=1. However, in Nuclear physics, the conservation of angular momentum in case of Gamma transitions is employed as follows:$$\vec J_i=\vec J_f+\vec L where $J_i$ is the ...
I'm curious about what happen to a system when the configuration of the system changes. If we have a system in a state $|\psi_{\textrm{in}}\rangle$ and we change the configuration of the system, the ...