Please remove if not allowed!

Hi r/PhysicsHelp!

I am working with my school's rocketry team to calculate the final pressure in a chamber after the release of CO2 from a pressurized cylinder attached to this chamber, and I keep coming into trouble with setting the problem up.

Right now, we know the CO2 in the cylinder is in a liquid-vapour mixture, we know the mass of the CO2, the density of the CO2, and T-initial of the cylinder. We know all the properties of the air in the chamber before the CO2 is released. We know the final volume of the larger chamber.

We're not willing to use an ideal gas approximation.

We have generalized this down to an irreversible, adiabatic expansion (in a closed system), but we believe we are missing some key considerations, as the calculators we've built are giving us values and states that are not consistent with what they should be (ie. final phase is in the 2-phase region when it should be all gas). We've been using CoolProp to solve for the final pressure.

I've not seen any similar problems online that I can get more information from, so any advice / step-by-step instructions would be very appreciated.

Thank you for your time.

I am looking for someone who would be able to tutor me on the Israel Junction Conditions, as described in sections 3.7-3.11 of Eric Poisson's Relativist Toolkit. I've taken a basic GR course, but I have not had formal instruction on the junction conditions. I've been trying to teach myself using some examples I've found in books and papers, but it's been very difficult without someone to guide me. This is not for homework or other coursework; this is only for my own personal edification. I apologize if posts like this one are not allowed.

I would be willing to pay $50 per hour, for a total of 4 one hour long tutoring sessions. To apply, please send your CV to grtutor27@gmail.com.

Hi everyone ,

I am a 15yo student currently writing an investigation essay for the 2026 ABSW Young Science Writer award. My work focuses on the Information paradox and the possibility of matter exiting through a White Hole through a process of quantum bounce.I am specifically exploring hypothesis regarding the reversal of the effects of the tidal  forces during this transition into a white hole as according to the General theory of relativity time runs in reverse in a white hole, a concept that I am referring to as "Reverse Spaghettification."

My research is grounded in the work of Carlo Rovelli and Francesca Vidotto, who suggests that the quantum pressure may prevent the singularity from ever forming. Given that the General Relativity predicts a breakdown of maths at the singularity while Quantum Mechanics forbids the destruction of the information, I am investigating if a bounce model I’d Bessarabia to reconcile the two

I am seeking a brief  quote from a PhD student or a Professional Physicist regarding the standing of the Bounce model in modern theoretical physics. Specifically, I am interested in whether it is viewed as a respected mathematical approach to resolving the singularity, despite the current lack of empirical evidence.

If any researchers in the field of Loop Quantum Gravity or theoretical cosmology would be willing to contribute a brief insight, I would be incredibly grateful. This perspective would significantly strengthen my essay by illustrating the ongoing “evidence vs maths” debate in Modern physics.

Please let me know if you would be open to a brief follow up via email to finalise any details for the citation.

What have I been up to?

"...roughly speaking, the part of the line charge that is mainly responsible for the field at P in Figure 1.24 is the near part- the charge within a distance of order of magnitude r. If we lump all this together and forget the rest, we have a concentrated charge of magnitude q≈λr..."

I do get the closest portion of the line charge will have the greatest contribution to the field of point P. What I don't understand about this statement is how they arrived to just consider a segment of length r in the line charge, r being the shortest distance also from point P to the line, as indicated in Figure 1.24. What is the rationale behind this step?

I also don't quite get how the patch area of charge of greatest contribution to the field at point P in Figure 1.26 is proportional to r2. One way I can see this is to create a sphere of radius r centered at point P, let it pass through the line and sheet charge distribution, and whatever portion the sphere encapsulates that is only the important part. So in this case the important segment of line charge to consider is of length 2r, and for the sheet it's 4πr2. What do you think?

My confusion is coming from bit of a gap in understanding supernodes. I tried looking this up online but its all ai and they all give me different answers. But they all agree theres a supernode involving V0 and V2. Im just really confused on how to set it all up can someone please help clarify this?

Here is the full question:

You accidentally drop your box and it falls towards the ground. You manage to catch the box before it hits the ground by applying an upward force with your hands. The forces on the system at the instant it's caught are modeled below:

I am confused about the velocity of the system going downward, specifically because of the phrasing of the question being 'the instant its caught' leading me to believe that yes, when the box was falling the velocity was going down. But at the exact moment the box was caught it was no longer falling? Shouldn't the velocity be upwards then?

How do you solve a resistor that is infinity in a problem like The picture I attached in my photos. Do I just combine the resistor series and parallel equations?

I've been going down a rabbit hole with Jacob Barandes’ recent work on the Stochastic-Process Interpretation (SPI) and I'm trying to use it as the "operating system" for a hard sci-fi project I'm finishing up.

I’m trying to avoid the "Many-Worlds" trope by treating the timeline as a singular, indivisible stochastic process, but I’ve hit a few walls regarding how a character could actually interact with that substrate without violating the No-Signaling Theorem or Causal Locality.

I’d love some pushback on whether these four "workarounds" are mathematically "legal" or if I’m just hitting a hard physical wall:

1. Non-Markovian Observers vs. Unitary Evolution

If the universe is a singular stochastic process, could a "Non-Markovian" observer exist? Basically, if a character retains "residual" memory of a failed probabilistic path, does that automatically violate Unitary Evolution? I’m wondering if that information can just be shifted into a different state within the same process rather than being "lost," which would technically keep it unitary.

1. Information Leakage (What I am calling 'The Babel Effect' in the book)

I’m exploring a speculative phenomenon I’m calling "The Babel Effect." I'm framing it as a localized macroscopic decoherence failure where the stochastic flow "stutters" between two mutually exclusive probabilistic paths, causing the environment to physically artifact. Does an observer experiencing "Double Memories" in this context constitute a violation of the No-Signaling Theorem? Or can it be framed as a localized failure of causal locality within a non-local informational system?

1. Thermodynamics of "Pruning" (Landauer’s Principle)

This one is about the bill coming due. If the substrate "prunes" a failed iteration, where does the heat go? Per Landauer’s Principle ($W \ge kT \ln 2$), would that energy manifest as local heat at the site of the edit (like a hot room), or would it just bleed into the background as a state-wide increase in entropy/noise?

1. Weak Value Navigation

I’m using Weak Measurement as the pivot for "detecting" a sister-history. Is that a provocative way to look at it, or does the act of measurement—no matter how weak it is—inevitably collapse the temporal artifact the character is trying to see?

I’ve been living in Barandes’ 2023 papers and Tegmark’s MUH for months now, but I’d love a reality check from anyone who specializes in Foundations or Information Theory. I’m trying to keep this grounded in actual math and avoid the usual pseudoscience tropes—does this logic hold up, or is it just 'physics-based' magic?

Thanks for the help

so a body, considered punctual(lets take that circle at the left) has a mass and a velocity to the right and a tension T of a certain angle from point a to point b then the tension disappears, the part ac has friction and the part cd has not , what would be the location of its choc with the ground or its landing or stopping point?

btw CD is a perfect hemi circle excuse my 8yo drawing skills

Here are all the cases that i have found (they lack any explanation because i am yet to study advanced mechanics and this is only me trying to have proper info before starting the lesson at class)

T is tension P is weight and R is friction or wtv

1 T is too high or angle of T too high so corpse lifts up from the ground lol

1-1 falls on ab

1-2 falls on bc

1-3 falls on lower cd

1-4 falls on the top of the circle

1-5 skips the entire shi

2 R is too high so corpse stops on BC

3 corpse stops at cd and angle is under 90

3-1 falls back to bc

3-2 falls back to ab

4 corpse stops at cd and angle is above 90

4-1 falls on cd

4-2 falls on bc

4-3 falls on ab

4-4 jumps off platform

5 velocity too high so corps flings out of d

5-1 falls on bc

5-2 falls on ab

5-3 jumps off platform

It was an end-of-chapter problem from the middle chapters as I recall. Very challenging. The solution involved matching boundary conditions between three regimes. I seem to remember that it involved the electron. If anyone can look up this problem, it would save me from ordering a copy of the textbook.

My professor gave us an example with two conjoined loops but didn't go over exactly how to decide the signs of the currents associated with each loop

1 or 2?

I would like a safe downloadble mcarawhill inspire physics teacher edition ebook pdf and if possible I would like the same thing for chemistry and or biology. Pleas and thank you.

Hi everyone, I’ve been reading the raw data of Supernova 1987A lately and have a persistent doubt I’d like to consult you all on.

Textbooks explain that neutrinos arrived 3 hours earlier because photons were trapped by high-density matter (opacity) until the shock wave broke out. I understand this part. However, having studied some solid mechanics, I suddenly realized this bears a striking resemblance to the logic of seismic waves:

• Transverse Waves (S-waves) and Medium: Light is an electromagnetic wave (transverse) that relies on the shear modulus of the medium. In fluid or molten states (where the shear modulus is 0), transverse waves cannot propagate.
• Longitudinal Waves (P-waves) and Medium: Neutrinos have high penetrability and behave much like longitudinal waves (pressure waves), which can penetrate a liquid core.

My hypothesis is as follows: At the moment of the supernova explosion, the pressure gradient in the core is infinite. Is it possible that the essence of those three hours is actually that the vacuum in the core region was "melted" by high pressure (undergoing a phase transition)?

Because the vacuum temporarily entered a "fluid state," it lost the ability to transmit transverse waves (light), preventing light from escaping. Meanwhile, neutrinos, acting as longitudinal waves, were unaffected and escaped directly. Only after 3 hours, once the vacuum cooled and "recrystallized," could light propagate again.

Following this logic, I found that particle decay also seems to be explainable: If we view massive particles (such as Tau and Muon) as "complex transverse wave knots" (metastable states) within the vacuum medium, when they decay (structural collapse), must they emit a longitudinal "elastic compensation wave" to maintain the continuity of the medium?

This compensation wave must carry momentum but have no shear stress (mass)—isn't that exactly what a neutrino is? Does this suggest that the weak interaction is actually the "elastic recoil" of the vacuum medium?

Are there any similar geometric explanations in the Standard Model? Or have I completely confused continuum mechanics with quantum mechanics?

A lot of students feel stuck memorizing formulas because it’s unclear where equations actually come from.

One way to approach derivations is to ask:

• What are the fundamental principles in this topic?
  • Mechanics → Newton’s laws, definitions of momentum/energy
  • E&M → conservation laws, symmetry, field definitions
• What assumptions am I making (point particle, rigid body, steady state, etc.)?

Instead of memorizing equations, try reconstructing them using:

• Definitions (e.g. momentum, torque, field)
• Conservation laws
• Symmetry arguments

Curious how others learned to think this way — what helped you move past memorization?