# All Questions

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### What is the use (/ meaning) of $F =ma$? [closed]

I have noticed that Euler's formula for force is useful with a couple of natural forces (at distance), like gravity, that can follow a body any length. If you consider the most common occurrences of ...
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I realise that the initial answer to my question that may come to mind is, "we don't know yet, obviously" But my question is hopefully not opinion based. For example, does this upgrade have a ...
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### What physical change has taken place in a solid, say ice, half way through a latent heat temperature verses time experiment?

During the classic high school latent heat experiment a solid such as ice is heated from below the melting point until it is a liquid above the melting point. During this experiment the temperature ...
359 views

### Why is the excited state of 116 Indium more stable than ground state?

Why is the excited state of 116 Indium more stable than ground state? Both undergo beta decay, but the ground state has a half-life of 14 seconds, while the excited state has a half-life of 54 ...
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### Higher spins elementary particles

Lorentz invariance requirement of theory imposes the absense of interactions between spin 3 and higher spins bosons and arbitrary field (like spin $\frac{1}{2}$ fermions etc) at least in infrared ...
117 views

### direction of friction on an object rolling with constant speed

Although there are many questions similar to this, but none of these specifically talk about the situation with constant speed. A wheel is rolling on a horizontal plane (having some friction) ...
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### Derivation of an ordinary, Lagrangian/Hamiltonian and action formulation

I am confused as to how the different formulations in physics are derived. In many fields of physics, we usually begin with an ordinary formulation (e.g Newton's Laws in classical mechanics), and ...
239 views

### Can change in temperature cause a change in mass of an object?

If a gold bar is heated to say 200 degree Celsius then will it have the same mass at say 10 degree Celsius. Does energy has mass? If so then does this increased 'heat energy' cause an increase in the ...
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### Understanding Quantum point contact

Am I correct in saying that quantum contact is : for a quantum heterostructure, by applying a voltage between two needle shaped split gate, it would deplete the electrons beneath it, therefore ...
4k views

### Thought experiment - would you notice if you fell into a black hole?

I've heard many scientists, when giving interviews and the like, state that if one were falling into a black hole massive enough that the tidal forces at the event horizon weren't too extreme, that ...
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### Summation notation for Kronecker delta

I'm having some problems on notation for indices: I've found in Goldstein, 3rd edition, that the Kronecker delta satisfies the following property: $$\delta_{ij}\delta_{ik}=\delta_{jk}$$ But ...
70 views

### Double-slit experiment, dielectric material containing the two parallel slits

This is concerning the double-slit experiment. This is concerning the material containing the two parallel slits. Are there experiments where the material containing the two parallel slits -- is ...
245 views

### Why do our ears pop?

Have you ever been on a train going through a tunnel or plane and your ears pop?I was wondering why this happens and I know it relates to pressure but don't know exactly the reason
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### Relative Velocity Help

I am struggling with relative velocity and so decided to do some extra problems in my textbook. I have 2 problems that seem to contradict, and its annoying things like this that throws me off, leaving ...
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### Why is $x=C\cos(\omega t)$ the solution of $m\frac{d^2 x}{dt^2}+kx=F_o\cos(\omega t)$ though lacking two arbitrary constants?

I was studying undamped oscillator with harmonic driving force at the steady-state condition. It can be expressed in the form of differential equation as:$$m\dfrac{d^2 x}{dt^2}+kx=F_o\cos(\omega t).$$ ...
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### How to properly implement Huygen's integral?

I'm really confused by what's happening ... I'm trying to propagate a beam some distance and compare initial and final intensities. Lets say the initial electric field is just cos(200x). I then used ...
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### Does special relativity happen in reverse when you freeze?

As you travel faster and faster you experience time at a slower rate, so if you travel slower and slower you should experience it at a faster rate right? My thinking is that even if you are ...
207 views

### Incompressible Navier-Stokes pressure solve in simulations

I am a complete newcomer when it comes to fluid simulations. I'm currently working through some tutorials to understand the idea of of the discretized Navier-Stokes equations for numerical ...
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### How fast do you have to be traveling in order to travel one light year in one year due to relativistic effects?

My apologies if my understanding is incorrect, but I believe that as you approach relativistic speeds you experience time dilation as compared to an outside observer. So taking into account this ...
62 views

### What exactly is conservative vector field?

I'm studying calculus, but since the example involved a physical concept. I will ask here: This is how it goes: This means that in a conservative force field, the amount of work required to ...
143 views

### Convert Temperature into Speed/Kinetic Energy

If the temperature of an object is simply a measurement of the average kinetic energy of the molecules within it; is it possible to convert the temperature of an object, given it's volume, into either ...
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### What is the entropy of strong and weak nuclear forces? [duplicate]

Can we determine the entropy of strong and weak nuclear forces? If so, what will be the formula to determine the strong and weak force entropy? Thank you :)
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### Does GR put a theoretical lower limit on the radius of a black hole event horizon?

Within GR theory, without going to the extreme r/0 as a radius, (but approaching that as an asymptotic case), is there any theoretical limit as to how small the event horizon of a rotating and/or ...
56 views

### Can you explain this “Theory of Everything”? [duplicate]

I recently come across with an amazing equation of Theory of Everything; I wonder if TOE has been formulated (???) I found this equation on a website, check it out ...
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### What are the consequences of a non-computable universe?

I have seen that is is debated if the universe is digital, computable or non-computable. what specific consequence could this have in the format of the laws of physics? Or would that mean that we will ...
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### What are possible explanations for the permeability of balloon rubber, PET plastic and other synthetic materials for carbon dioxide?

Balloons are definitely not gas-tight. Carbon dioxide just leak by the rubber away. A balloon is filled with carbon dioxide. Knot in it. And play. Shrinkage. After an hour or two the carbon dioxide ...
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### Is there a relationship between force and entropy?

Is there any relation between force and entropy? If any, I would like to know what the equation of this relation will be. What is the entropy of strong and weak nuclear force? Can we determine it? If ...
54 views

### Change of magnetic flux on size of magnetic field and area

Consider a solenoid with 50 turns. Each turn gives has an area $A$. When the power is switched on, each turn produces a magnetic field of 1 Tesla. What is the total change in magnetic flux when the ...
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### For an intrinsic semiconductor, why is fermi level half-way? [duplicate]

Why is the fermi level half-way between the conduction band and valence band?
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### Do particles have spin because there exist spinor representations for the Lorentz group?

I am reading Peskin and Schroeder's An introduction to field theory. They first describe the spinor representation of the Lorentz group, and then they mention the fact that different particles have ...