# All Questions

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### Why does surface tension of water-ethanol binary mixture decrease with increasing concentration of ethanol?

I was thinking that it must be due to weaker hydrogen bonding in ethanol than in water. But then I learnt that Raman Spectroscopy and viscosity measurements suggest that upto a certain ethanol ...
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### time as consequence of hadronics

it has occurred to me that time is solely consequence of non-electric fields, with latest work being reading about «anapole» cite: Simple theory may explain dark matter due to ...
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### Earth density distribution from shooting neutrinos?

I am interested in possibility of inferring Earth interior structure from gravitational data. As classical calculus problem shows, it is impossible to understand non-uniform density distribution ...
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### How to determine the angular velocity of a particle with mass $m$ and charge $q$ in a constant B field?

$\textbf{PROBLEM:}$ A particle with mass $m$ and charge $q$ moves in a constant magnetic field $B$. Show that, if the initial velocity is perpendicular to $B$, the path is circular and the angular ...
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### Is the electrostatic field really static? Does thermal vibrations not affect it?

We know that if a conductor has any net charge, the charges reside on the surface. The electric field immediately outside the surface is perpendicular to the surface. But the charged particles, say ...
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### How do you calculate the electric tension between two charged entities?

If: 1) you know the coordinates and individual charge(in coulombs) of each object and 2) voltage is the difference in electric potential energy between two nodes How do you calculate the voltage in ...
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### Is entropy a meaningful concept on a quantum level?

My naive assumptions, as I really am at a pretty basic stage in QM, are as follows: Classically, entropy gives us a practical measure of the direction of time, as opposed to our physical laws which, ...
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### longitudinal magnification confusion in concave mirror

If you move a rod lying on the principal axis of any concave mirror, when the near end of the rod is at a distance equal to half it's own length from the mirror, then the instantaneous velocity of ...
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### Any other mathematical fields in physics than $\mathbb{R}$ or $\mathbb{C}$?

In physics, we usually use the real number field $\mathbb{R}$ or the complex number field $\mathbb{C}$. Does any other field find use in physics too?
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### BiCopter simulation problem [migrated]

I derived bicopter dynamical model with two servos and two BLDC motors. And now am trying to simulate it using Matlab. As base for simulation I used this paper and this code: ...
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### Centripetal Force Doubt

I have'nt understood the solution that has been provided: Question: Solution : I did'nt understand the part where they stated that for the water to not fall out of the bucket, N>= 0 I'm a high ...
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### Is the MaxEnt “interpretation” of statistical mechanics the current mainstream approach?

I've only recently started studying statistical mechanics and I'm quite confused with the MaxEnt and anti-MaxEnt ideas. I'm looking for a concise answer, if it is possible, not really a description or ...
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### Tensors, indices and matrix notation - is there a common convention?

For a tensor named T with two indices, there are four possibilities: $T_{ij}$ , $T_i^{\ j}$, $T^i{\ _j}$ and $T^{ij}$. Is there a common convention as to how these tensors would be represented as ...
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### If a probe barely escapes a black hole doesn't its clock slow down?

That is, wouldn't a probe traveling just far enough away from a black hole to not fall in show less time on it's clock compared to the spacecraft when it returned (gravity time dilation)? If so, ...
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### How is ampere defined for alternating current?

Both alternating current and direct current are measured in ampere. But how is ampere defined for alternating current? It cannot be defined from two mutual attraction of two parallel wires carrying ac ...
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### can light bounce off another light?

If light is a wave and a particle (wave particle duality), is it possible for light to bounce off another light since light bounces of another matter(particle)?
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### Regarding IMU derivation of position/orientation

If you are familiar with IMUs (Inertial Measurement Unit) , you know that before the double integration to arrive at estimating the position, one has to subtract the gravity from the measured ...
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### How do you calculate minimum speed for a mass to move vertically in a circle

For part c) would you subtract the top and bottom tensions to find the minimum velocity. The answer should =2.7 m/s for part c).
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### Is there free will? [on hold]

From what I've understood about the answer to this question quantum physics doesn't contradict determinism, but instead it simply isn't achievable only because of our universe's nature: we are unable ...
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### Differentiation of a vector with respect to a vector

Does differentiation of a vector with respect to a vector make any sense? Even if it makes sense, how does it make any physical meaning? I mean what is the physical interpretation?
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### Certain doubts regarding the facts shown in 'Interstellar'

In the movie, or rather a scientific fiction, Interstellar, we saw in the last part, that the actor falls into the black hole, travels in time, which is a dimension inside the black hole, and then, ...
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### Light Spectrum - Sum of Waves or Collection of Waves

I'm wondering about the spectrum of light that is often shown pictorially as a distribution of power, say, from sunlight. My question is: does this indicate that each wave of light contains all of ...
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### Block over a Block Problem.

This a block placed on block problem. In this problem, A block with mass 40 kg in placed on a block of 60kg which lies on a frictionless surface. The coefficient of friction between 40kg mass and 60kg ...
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### Does a switched on power socket consume electricity? [migrated]

Lets say I have a TV and a power socket but the TV switch is off however the socket switch is switched on, so will it consume electricity?
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### Why does in the definition of 'optical path', only spatial phase change is taken into consideration & not that of time?

In Concepts of Physics by H.C.Verma, I got the definition of optical path. However, one thing that I couldn't understand is why only the spatial phase change is considered in its definition. As he ...
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### How to calculate the linear speed without angular velocity

How would you calculate question (f) the linear velocity, without a angular velocity. The radius of the circle is 0.6m. The answer (linear velocity) should = 1.84 m/s
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### Is work done by a pseudo force?

If a body is viewed from the frame of another body which is itself accelerating will work be done by the pseudo force acting on first body in the frame of second body ( provided the first body is ...
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### Are the particle-antiparticle pairs produced in vacuum virtual particles, and can they interact with normal particles?

If it is true that due to energy fluctuations of a vacuum being able to produce a particle-antiparticle pair that shortly annihilate with each other and disappear again, is the following circumstance ...
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### Laser Energy Level Transitions

I am new to Laser Physics. While looking at the Energy Levels diagram for the Laser Transition of ND:YAG laser, I see energy levels labeled like 4F(3/2), 4I(15/2),.. I did not come across such energy ...
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### Why is a vertex a derivative of the propagator?

Where can I find the answer to my question: if the momentum is small, the vertex is the derivative with respect to the mass of a propagator times a factor (-m/v) like in the picture:
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### Radio active isotopes [on hold]

Radio active 54fe at mass 15g is given activity of 3700000 meters per second and then inserted into an engine.After 100days of continuous use,the crank case oil was found to have a total of activity ...
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### Formula connecting Force and Power

Is there such formula? There probably is of course, but i would like a very concise description of how to derive it, in order to better understand myself. Thank you in advance.
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### Tesla coil arc in air - where is it going?

here is a picture of a Tesla coil with a discharge that seemingly terminates in the air. What completes the circuit at the end of the streamers?
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### Diffraction experiment at home

I have bought a laser tachometer, can you tell me if it is possible to make a diffraction experiment at home? How can one make a slit of 630 nm? As a side question: light bouncing on reflective tape ...
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### How to reduce cooling time of hot aluminum casting / block?

I am doing project on "reduction of cooling time of hot Aluminium casting/block". Aluminum casting / block temperature is 250degree C (532 K), size diameter 600mm x 150mm and weight 25kg. In order ...
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### entropy balance equation in thermodynamics [on hold]

can any body help me to prove the following entropy balance equation. $$T \frac{ds}{dt}=- div \mathbf{q}$$ where $T$ is absolute temperature and $s$ is entropy $\mathbf{q}$ ...
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### water permittivity

I made a water sondе from one sided FR4. The plates are parallel, copper sides are counterclaims. The plates are $5\times 50$mm, spaced at $7.5$mm. The expected value of capacitance is ...
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### Fourier expansion and transform - what about the phase of the waves that i am adding?

Say we have a wave on the surface of the water and we want to describe it as a sum of other waves. So we use Fourier expansion to add waves of different wavelengths. For simplicity, say we have to ...
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### Black Holes and Einstein Field Equations

I recently watched a video where Michio Kaku argues that there must be something fundamentally wrong with the theory of General Relativity because it gives time t=0 as a solution at the centre of a ...
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### An experiment at home: cinematic 3d [on hold]

I would like to know if I'm right when I experiment this at home: The support (grey color) turns. The purple disk don't turn around itself at start but it can. The point A is fixed on the purple ...