# All Questions

134,983 questions
78 views

60 views

52 views

### Relativity of Simultaneity Confusion [on hold]

An electron is emitted from a nucleus at a speed of $0.975c$ as observed in a laboratory frame of reference. The electron is detected at a distance of $0.800$ $m$ from the emitting nucleus as measured ...
22 views

### How much conduction, radiation and convection influence in a thermos flask?

It has been thoroughly repeated that thermos flasks prevent heat loss by minimizing heat conduction, radiation and convection from the bottle to its ambient. This has been answered in this SE. However,...
25 views

### Computation of Feynman integrals in terms of Chen Iterated integrals

One of the techniques used to compute Feynman integrals in dim-reg is the so-called "differential equations method". Exploiting integration-by-parts identities (linear functional relations between ...
34 views

### Einstein equations algoritms solutions [on hold]

My question is, is there an Einstein equation's calculation algorithm, and what is Einstein's 10 equation system?
82 views

### Relativity Confusion

In the time dilation formula $\Delta t=\gamma\Delta t_0$, I am confused about what $\Delta t$ and $\Delta t_0$ measure. If we have two people, Tom and Bob, moving at constant velocity relative to ...
90 views

### How propulsion in the “HELPING HAND” NetFlix episode works? *SPOILER*

I watched the "HELPING HAND" episode in NexFlix, and the protagonist is drift in space, every second she is more far from her ship, when her tank is out of oxygen, she throw her glove to make a ...
15 views

### Fly wing velocity question [on hold]

A fly beats its wings at a frequency of 1200 Hz. if the expansion and contraction of the wing muscles of the fly exhibits simple harmonic motion, the angular displacement of each wing of the fly also ...
42 views

### Why does current not increase when the voltage increases in this case? [migrated]

When talking about BJT transistors, a very common graph is the one shown below, that plots (VCE,IC) as an ascending function. As far as I know, the BJT manages VCE so that IC is beta times IB, being ...
17 views

### What are dark excitons and how to find them?

I am reading about excitons and I encountered a few times the term "dark exciton" but I have a hard time finding a good definition. I tried to google it but I only find scientific articles where the ...
21 views

### What exactly sets the scale in Fusion power plants?

In fusion power plants, larger devices are said to achieve fusion more easily, next step tokamaks like DEMO are even larger than ITER. In a quantitative way, what exactly isn't scale invariant in a ...
21 views

### The ideal shape of a plano-convex lens

What's the type of the ideal shape of a surface of a plano-convex lens to focus a parallel beam at the point? Considering the lens turned its flat side to a beam. Surely it must be aspheric: ...
7 views

### What is the twist 2 sector of nucleonic parton distributions?

I am on the evolution of transversity distributions in QCD. And in the papers everyone talks about twist 2 sector and leading twist corrections. I can't find anything about twist. Do they talk about ...
41 views

### Assumptions and limitations for ideal gas

Assumption: In the assumption for ideal gas law, it is stated:"The time it takes to collide is negligible compared with the time between collisions." For, this assumption, can i just say there is only ...
57 views

### Could a trajectory around a large mass ever deflect by more than 180 degrees due to general relativistic effects?

Possible mechanisms that could be an answer to the question What natural mechanisms could lead to the unlikely case of the same rogue asteroid or planet passing through our solar system twice? include ...
24 views

### Torque contacts

I experienced yesterday that when the slotted screw driver head was exact fit to the slotted screw, it was easier to turn the screw. I'd like to understand the physics of it. Is the bottom easier to ...
20 views

### How does the momentum conservation law hold for gravitational interactions in special relativity with Newton's third law being invalid?

Griffiths' argument that Newton's third law is invalid in special relativity The selected answer to the post above talked about momentum conservation in electrodynamics – Newton's third law ...
589 views

90 views

### Why doesn't a force perpendicular to the direction of motion change the speed?

It changes direction but not speed and this is proved in experiments. But is there any more "deep" reason as that space has isotropy and energy must be conserved per example?
21 views

### How to simulate plane Poiseuille flow using Molecular Dynamics? [on hold]

I want to simulate 2D plane Poiseuille flow using molecular dynamics (velocity verlet algorithm) but not able to understand exactly to how to do this. Boundary condition is fine, I am confused about ...
17 views

### How to perform an isothermal reversible expansion?

Take the case of an isothermal reversible expansion of a piston to lift a weight. As the piston expands, the temperature remains constant, but the volume increases. This volume increase implies a ...
20 views

### How to find Kinetic energy of the block of mass M?Please provide a detailed solution [on hold]

(https://i.stack.imgur.com/FcsvD.jpg)(https://i.stack.imgur.com/W0BE0.jpg) The spring of force constant k2 just touches the wall and is not attached to the wall.The natural lengths of the strings are ...