# All Questions

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### Does a point mass have constant mass?

Expanding on the title, I am hoping for a little bit of insight into the philosophy of Newton's mechanics as a physical theory. My question, essentially, is does a point mass have constant mass by ...
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### Does an excitation of any quantum field extend forever through space?

For visualization purposes, let’s say I slam my hand into sheet metal and it vibrates. Will that vibration extend beyond the metal sheet into the space surrounding it, and would that energy wave ...
1 vote
12 views

### Is weak hypercharge carried by Z boson?

In the PBS spacetime video about charge (https://m.youtube.com/watch?v=esayi49OAk4&feature=youtu.be), at 10:55 he said that weak hypercharge is carried by the Z boson. Is this accurate?
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### How would power the baby Yoda (Grogu) Pod? [closed]

Lets go wild! Throw in your theories and ideas how you would power such a floating device? Lets have some fun wild theories!
15 views

### If two equal and opposite charges are not taken apart why they are considered as neutral .and what is neutral

If two equal and opposite charges are not taken apart why they are considered as neutral and what is neutral, charge or field
51 views

### Have I found evidence that a megaparsec is a fundamental distance and not an arbitrary one? [closed]

If I take the expression for the radius excess of the Earth from general relativity and swap the gravitational constant G for the coulomb constant K and use the total electric charge of the protons in ...
16 views

### Why the Hubble parameter that is proportional to dark energy is squared in the Friedmann's equation?

I'm studying Alexander Friedmann's equation about the Hubble parameter and, thus, the time dependence of the cosmic scale factor varies as the matter density, ρ, and as the dark energy, Λ as shown in ...
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1 vote
25 views

### Hand-wavy method to ampere's law for a single coil of wire

Based on this question Ampere's law and Biot-Savart law gives different terms for magnetic field in middle of a current running in a loop I made the following square Amperian loop: where I have ...
• 909
16 views

### Period of small amplitude oscillations [closed]

So I am trying to do a question where I have two objects that are rolling without slipping. We have found the potential function for this setup, have found the H, we are given y and we're also give ...
• 21
4 views

### Is there an analogous method of finding moment for inelastic bending like in the case of inelastic torsion?

When calculating for Torque in torsion or for Moment in the case of bending, the concept is usually first introduced with the simplification of the assumption that the stresses and strains are in the ...
20 views

### Aperture/image circle in a DIY digital microscope?

I have just taken apart a broken USB microscope, and recognized that there is actually no magic going on inside. So I thought how about building one of my own. The idea is to buy a regular (possibly ...
• 7,230
39 views

### Can FTL be done in a way that it dosen't break causality? [closed]

So I was wondering if we could travel faster than the speed of light without creating time paradoxes?could we achieve FTL in a certain way that it dosen't break causality?or does FTL always break ...
1 vote
34 views

### What are non-propagating degrees of freedom? [closed]

I have read at different places that in 3 spacetime dimensions, there are NO propagating gravitational degrees of freedom. This seems to imply that we have only "non-propagating" degrees of ...
• 229
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### Doubt in expansion of integral

While solving for the chemical potential of a fermi gas at $T\ne 0$, we first take $$n = \int_0^{\mu}g(\epsilon)d\epsilon+(\pi^2/6)(k_BT^2)g'(\mu)+O(T^4)$$ Which is obtained by the Sommerfeld ...
• 193
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### The problem of the density of the induced charge on a dielectric cylinder. Why is my solution wrong? [closed]

Why is my solution wrong? Task: The dielectric cylinder is in an external uniform electric field E, which is parallel to the axis of the cylinder. Find the surface density of the charges induced on ...
24 views

### When two neutron stars collide to form a black hole, for how long will last the emitted signal from the very vicinity of the new formed event horizon?

When two neutron stars collide they may form a black hole which is not a supermassive black hole but it should provoke that outside its newly formed event horizon photons are emitted as a consequence ...
• 2,173
46 views

### Energy conservation in a driven harmonic oscillator

The ODE for a driven harmonic oscillator is given by $$\ddot{x}+2\gamma \dot{x}+\omega_0^2 x = \frac{F}{m}\cos(\omega_dt)$$ By assuming balance of forces, i.e. energy conservation, one can solve for ...
1 vote
32 views

### What is the boundary from N to S called in magnetism? [closed]

I am doing some research on asymmetric magnetic fields. I have simplified my problem to an isosceles triangle mangnetized with the N side on the tip with the smallest angle and the S side opposite of ...
37 views

### Is the free Hamiltonian unique (as defined in Weinberg vol 1 chap 3)? [closed]

In chapter 3 of Weinberg, he defines asymptotic states by first splitting up the full interacting hamiltonian as $$H=H_0+V$$ where $H_0$ is the free Hamiltonian. He makes a point of saying that ...
• 1,775
19 views

### Will the ideal gas equation change if we consider non equillibrium condition and then use kinetic approach and thermodynamic approach?

My teacher said that in equilibrium no matter what approach we use we arrive to same result i.e. in this case ideal gas equation. So if we were to use the two approaches (thermodynamics and kinetic ...
34 views

### Why doesn't the sun appear to move backwards when we move forward? [duplicate]

I have observed that while travelling (in a train, for example), as the train moves forward, all the objects in the surrounding environment seem to move backwards (like the trees). However, if we ...
• 446
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### The combined gas law and the ideal gas law

This might sound a bit weird, but I do not understand what I am missing! We have the combined gas law: $$PV/T$$ And the ideal gas law: $$PV/nT$$ My first question is that why didn't French physicist ...
1 vote
40 views

### Calculating change in Momentum

A 100g ball with a speed of 5m/s hits a wall at an angle of 45 degrees. The ball then bounces off the wall at a speed of 5m/s at an angle of 45 degrees. What is the change in the momentum of the ball? ...
38 views

### Quantum physics book good explanation with minimal maths [duplicate]

Kindly suggest quantum physics book good explanation with minimal maths. I read once beginning of such a book with good explanation and minimum maths but am forgetting book name. Maximum suggestions ...
25 views

### How to create a more accurate gravity simulation? [duplicate]

Goal: I am interested creating a simple gravity simulation and was wondering if it was possible to describe two objects motions through time with percision. All other parameters are known (...
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### Tensionless string in Nambu-Goto action

I am studying string theory from the book "String theory and M-theory", written by Becker, Becker and Schwartz. My question is: We are taught that one of the advantages of introducing a ...
• 2,815
48 views

### Where does it's gravitational force come from to maintain its constant somewhat spherical shape? [duplicate]

How dose a Tidally locked gas giant have a balanced gravitational force to keep it's spherical shape when one side is constantly facing the sun? Where does it's gravitational force come from to ...
18 views

### Proper acceleration along perpendicular directions

Let's take an object (all times mentioned in this problem are proper times). There is a constant proper acceleration "$a$" on this object in the x-direction for time $t, 0\leq t \leq \tau$. ...
20 views

### How does the increased binding energy per nucleon help in stability?

I have some read answers on this forum, some books like Halliday Resnick and my course books. I have understood that binding energy is the energy we need to supply to break nucleus into individual ...
24 views

### One homework about berry phase [closed]

I have a homework problem that I don't even know where to start. Could anyone give me at least some hint to start? I can now use the ansatz given in the problem, and then write \$|\Phi(T)\rangle=e^{i\...