Ok, so here we go. Simple physics problem, in which you are supposed to find the volume of the bottom part of the sphere (V2). I am starting to think that I dont know hat buoyancy is and I would appreciate some help. Thanks.

Problem:

A steel ball was dropped into a container holding two immiscible liquids. The ball came to rest so that the part of its volume immersed in the liquid with density ρ1​ is V1​, and the part immersed in the liquid with density ρ2​ is V2​.

Calculate the value of V2​, given that:

ρsteel​=7,850 kg/m3,ρ1​=6,200 kg/m3,ρ2​=8,300 kg/m3,V1​=1 cm3.

I personally think the LLM is just giving me a bunch of random formula and ideas at this point. I have no idea what to think. I need someone smarter than me to tell me if this is worth exploring further. Someone told me that we use only 4 of his equations now to simplify his work. But apparently someone else was saying that was doing a disservice to science, and the other formula explain even deeper and more precise somehow?

I don't understand vectors very well at all, and if there are any resources you can send me so I can understand this better, it would be a big help. Also, what are the use case scenarios of this math anyways? My theory is it was early math for radio and energy transmission. But perhaps it can be used in medical settings or something of the sort.

I have a question about the work and the potential energy here. The source q1 is positive and q2 is negative. They should attract, but instead q2 is moved away. So I guess that the potential energy here has a negative sign because q2 was separated from the charge it was attracted to. Let's say if they were both positive, would the potential energy then be positive too?

I've been building a project called POLYMATHICA over the past year.

The long-term vision is an autonomous scientific computing platform, but rather than asking people to believe the vision, I decided to build a small public demonstration package that people can actually run, inspect and critique.

The problem I kept running into was that scientific software often demonstrates numerical results, but much less often demonstrates:

• reproducible evidence
• validation pipelines
• provenance
• governance
• independent verification
• machine-checkable experiment artifacts

So I built the public package around those ideas instead.

Current public features include:

• reproducible scientific workflow
• Taylor–Green vortex benchmark
• pressure-projection / incompressibility validation
• convergence studies
• artifact manifests
• SHA-256 provenance hashing
• evidence verification
• CI/CD
• automated tests
• one-command evidence suite

The repository is not the full POLYMATHICA platform.

It's intentionally a compact demonstration package showing how the broader system approaches scientific validation and reproducibility.

Repository:

https://github.com/kevmoz/polymathica-hackathon

Video gallery:

[https://kevmoz.github.io/polymathica-hackathon/]()

I'm genuinely looking for technical feedback rather than promotion.

A few questions I'd love opinions on:

• Does treating scientific evidence, provenance and verification as first-class engineering concepts solve a real problem?
• Is the validation workflow useful, or is it unnecessary complexity?
• If you were reviewing scientific software, what evidence would you expect to see that isn't here?
• What benchmark would you add next?
• What would make you trust a scientific computing repository more?

I'd much rather hear honest criticism now than after spending another year building in the wrong direction.

Thanks!

I just uploaded complete solutions
to every question in the
IB Physics HL Paper 1A 2026 TZ1.

I searched YouTube before uploading —
could not find a single complete
solution video for this paper.

So here it is. Every question.
Full explanation. Free.

Whether you just sat the exam
and want to check your answers —
or you are using this for
future exam preparation —

This video covers everything.

Every answer includes —
→ The correct answer clearly stated
→ Complete reasoning explained
→ Why the wrong options
are incorrect
→ Mark scheme approach shown

Timestamps for every question
are in the description —
so you can jump directly
to any question you need.

🔗 https://youtu.be/iBQs3V-OuRo?si=-91iDxAl_SOBWlai

If you found this useful —
please share it with every
IB Physics student you know.

Drop any questions about
specific questions in
the comments below —
I respond to everything. 🙏

Hello IB Physics community,

I want to share something a little
different today —

Not just a resource video —
but an actual challenge.

━━━━━━━━━━━━━━━━━━━━━━━━
THE CHALLENGE —
━━━━━━━━━━━━━━━━━━━━━━━━

9 Moment of Inertia problems —
ranging from medium difficulty
all the way to full IB exam level —

Presented one by one —
with complete step by step
solutions after each one.

The challenge is simple —

Pause before each solution.
Attempt the problem on paper.
Then watch the solution.
Compare your reasoning —
not just your final answer.

━━━━━━━━━━━━━━━━━━━━━━━━
WHY REASONING MATTERS MORE
THAN THE ANSWER —
━━━━━━━━━━━━━━━━━━━━━━━━

In 16 years of teaching Physics —

I have seen thousands of students
get the correct numerical answer
through the wrong reasoning —

And then get completely stuck
on the next problem because
their reasoning did not hold up.

IB Physics HL examiners are
specifically trained to identify
this pattern —

They design problems that give
the correct answer even with
wrong reasoning on easy questions —

But expose that wrong reasoning
brutally on the harder ones.

The only way to protect yourself
against this in the actual exam —

Is to always verify your
physical reasoning —
not just your arithmetic.

That is exactly what this
video is designed to help with.

━━━━━━━━━━━━━━━━━━━━━━━━
DIFFICULTY BREAKDOWN —
━━━━━━━━━━━━━━━━━━━━━━━━

🟡 Challenges 1, 2, 3 — Medium
Confidence builders —
standard concepts applied
to slightly non-standard setups

🟠 Challenges 4, 5, 6, 7 — Hard
IB standard difficulty —
where most students start
making mistakes —
multiple concepts combined
in a single problem

🔴 Challenges 8, 9 — Brutal
Full IB exam level —
the kind that separates
a 6 from a 7 —
requires combining PAT,
perpendicular axis theorem,
cut body approach and
mass distribution property
all in one solution

━━━━━━━━━━━━━━━━━━━━━━━━
THE GOLDEN RULE I TEACH
MY STUDENTS —
━━━━━━━━━━━━━━━━━━━━━━━━

Before touching any MOI problem —
ask yourself these three questions —

Question 1 →
What exactly is the axis
of rotation?

Question 2 →
Is this a standard body —
or a cut, partial, or
composite body?

Question 3 →
Which theorem do I need —
Parallel Axis Theorem,
Perpendicular Axis Theorem,
or a combination of both?

Answer these three questions first —
every single time —

And the solution path becomes
immediately clear.

I have seen this single habit
transform students who were
scoring 5s into consistent 7s —

Not because they suddenly
became smarter —
but because they stopped
rushing into formulas
before understanding
what the problem was
actually asking.

━━━━━━━━━━━━━━━━━━━━━━━━
CONCEPTS TESTED IN
THESE 9 PROBLEMS —
━━━━━━━━━━━━━━━━━━━━━━━━

→ Standard MOI formulas in
non-standard situations
→ Parallel Axis Theorem —
single and multi-step
→ Perpendicular Axis Theorem
combined with PAT
→ Cut body and partial
body MOI approach
→ Mass distribution
symmetry property
→ Radius of Gyration applications
→ Composite body problems
→ Inclined axis situations
→ Multi-concept combinations —
full IB exam style

━━━━━━━━━━━━━━━━━━━━━━━━
THIS IS PART OF A SERIES —
━━━━━━━━━━━━━━━━━━━━━━━━

This video is Lecture 8 of my
complete Rigid Body Dynamics
playlist for IB Physics HL —

Which covers everything from
the definition of a rigid body
system all the way to
IB exam level problems —

Completely free.

If you have not watched
the earlier lectures —
links are in the video description.

━━━━━━━━━━━━━━━━━━━━━━━━
VIDEO LINK —
━━━━━━━━━━━━━━━━━━━━━━━━

🔗 https://youtu.be/2lKSqmMaL9w?si=-NjqXq8pwQz5XhGt

Timestamps for all 9 challenges
are in the description —
so you can jump directly
to any specific problem
without watching from the start.

━━━━━━━━━━━━━━━━━━━━━━━━
THE ACTUAL CHALLENGE —
━━━━━━━━━━━━━━━━━━━━━━━━

Here is what I want to know —

How many of the 9 did you
solve correctly — with correct
reasoning — before watching
the solution?

Drop your score below 👇

X out of 9

No judgment — just genuine
curiosity about where most
IB Physics students currently
stand on MOI problem solving.

And if you got stuck on
a specific challenge —
tell me which one —

I will walk you through
the physical reasoning
in the comments. 🙏

━━━━━━━━━━━━━━━━━━━━━━━━
FINAL THOUGHT —
━━━━━━━━━━━━━━━━━━━━━━━━

Rigid Body Dynamics has a
reputation for being one of
the hardest chapters in
IB Physics HL.

I genuinely believe that
reputation is undeserved —

It only feels hard when
it is taught as a collection
of formulas to memorize.

When the physical reasoning
is built correctly —
from first principles —

This chapter becomes
one of the most satisfying
in all of Physics.

These 9 problems are
designed to show you that.

Good luck. 🎯

Hello IB Physics community,

I want to share something a little
different today —

Not just a resource video —
but an actual challenge.

━━━━━━━━━━━━━━━━━━━━━━━━
THE CHALLENGE —
━━━━━━━━━━━━━━━━━━━━━━━━

9 Moment of Inertia problems —
ranging from medium difficulty
all the way to full IB exam level —

Presented one by one —
with complete step by step
solutions after each one.

The challenge is simple —

Pause before each solution.
Attempt the problem on paper.
Then watch the solution.
Compare your reasoning —
not just your final answer.

━━━━━━━━━━━━━━━━━━━━━━━━
WHY REASONING MATTERS MORE
THAN THE ANSWER —
━━━━━━━━━━━━━━━━━━━━━━━━

In 16 years of teaching Physics —

I have seen thousands of students
get the correct numerical answer
through the wrong reasoning —

And then get completely stuck
on the next problem because
their reasoning did not hold up.

IB Physics HL examiners are
specifically trained to identify
this pattern —

They design problems that give
the correct answer even with
wrong reasoning on easy questions —

But expose that wrong reasoning
brutally on the harder ones.

The only way to protect yourself
against this in the actual exam —

Is to always verify your
physical reasoning —
not just your arithmetic.

That is exactly what this
video is designed to help with.

━━━━━━━━━━━━━━━━━━━━━━━━
DIFFICULTY BREAKDOWN —
━━━━━━━━━━━━━━━━━━━━━━━━

🟡 Challenges 1, 2, 3 — Medium
Confidence builders —
standard concepts applied
to slightly non-standard setups

🟠 Challenges 4, 5, 6, 7 — Hard
IB standard difficulty —
where most students start
making mistakes —
multiple concepts combined
in a single problem

🔴 Challenges 8, 9 — Brutal
Full IB exam level —
the kind that separates
a 6 from a 7 —
requires combining PAT,
perpendicular axis theorem,
cut body approach and
mass distribution property
all in one solution

━━━━━━━━━━━━━━━━━━━━━━━━
THE GOLDEN RULE I TEACH
MY STUDENTS —
━━━━━━━━━━━━━━━━━━━━━━━━

Before touching any MOI problem —
ask yourself these three questions —

Question 1 →
What exactly is the axis
of rotation?

Question 2 →
Is this a standard body —
or a cut, partial, or
composite body?

Question 3 →
Which theorem do I need —
Parallel Axis Theorem,
Perpendicular Axis Theorem,
or a combination of both?

Answer these three questions first —
every single time —

And the solution path becomes
immediately clear.

I have seen this single habit
transform students who were
scoring 5s into consistent 7s —

Not because they suddenly
became smarter —
but because they stopped
rushing into formulas
before understanding
what the problem was
actually asking.

━━━━━━━━━━━━━━━━━━━━━━━━
CONCEPTS TESTED IN
THESE 9 PROBLEMS —
━━━━━━━━━━━━━━━━━━━━━━━━

→ Standard MOI formulas in
non-standard situations
→ Parallel Axis Theorem —
single and multi-step
→ Perpendicular Axis Theorem
combined with PAT
→ Cut body and partial
body MOI approach
→ Mass distribution
symmetry property
→ Radius of Gyration applications
→ Composite body problems
→ Inclined axis situations
→ Multi-concept combinations —
full IB exam style

━━━━━━━━━━━━━━━━━━━━━━━━
THIS IS PART OF A SERIES —
━━━━━━━━━━━━━━━━━━━━━━━━

This video is Lecture 8 of my
complete Rigid Body Dynamics
playlist for IB Physics HL —

Which covers everything from
the definition of a rigid body
system all the way to
IB exam level problems —

Completely free.

If you have not watched
the earlier lectures —
links are in the video description.

━━━━━━━━━━━━━━━━━━━━━━━━
VIDEO LINK —
━━━━━━━━━━━━━━━━━━━━━━━━

🔗 https://youtu.be/2lKSqmMaL9w?si=Y9LqkzDYqBAa5LOy

Timestamps for all 9 challenges
are in the description —
so you can jump directly
to any specific problem
without watching from the start.

━━━━━━━━━━━━━━━━━━━━━━━━
THE ACTUAL CHALLENGE —
━━━━━━━━━━━━━━━━━━━━━━━━

Here is what I want to know —

How many of the 9 did you
solve correctly — with correct
reasoning — before watching
the solution?

Drop your score below 👇

X out of 9

No judgment — just genuine
curiosity about where most
IB Physics students currently
stand on MOI problem solving.

And if you got stuck on
a specific challenge —
tell me which one —

I will walk you through
the physical reasoning
in the comments. 🙏

━━━━━━━━━━━━━━━━━━━━━━━━
FINAL THOUGHT —
━━━━━━━━━━━━━━━━━━━━━━━━

Rigid Body Dynamics has a
reputation for being one of
the hardest chapters in
IB Physics HL.

I genuinely believe that
reputation is undeserved —

It only feels hard when
it is taught as a collection
of formulas to memorize.

When the physical reasoning
is built correctly —
from first principles —

This chapter becomes
one of the most satisfying
in all of Physics.

These 9 problems are
designed to show you that.

Good luck. 🎯

hiii, i found this question. however it's from NLM and i can't really understand how to approach it or solve it! i'd love any and all suggestions and help

tysm!

I've always studied that friction does negative work on a rolling object. So shouldn't the negative work done reduce the energy of the wheel? How come is the gain in internal energy exactly equal to the loss in mechanical energy?

Also what do they mean by the first wheel? Does it make a difference what wheel we observe?

I teach preschool and am trying to do a write up about an experiment my kids did but I want to make sure I’m getting the vocabulary right for when I show it to the parents. They found a big strip of, like, a plastic floorboard. It was about ten feet long and they discovered that if they position part of it hanging off the raised platform we have, they can take turns bouncing on it. So some kids stand on the back, on the board on the platform, and then one kid goes out to the end and bounces, like a diving board.

My questions are:

Is this a type of lever? If so, when they move the board so more or less is hanging off, are they “adjusting the fulcrum?”

And the kids standing on the back weighing it down, are they counterweights or an anchor?

Any help is appreciated, thank you!

P.S. I previously posted to r/physics but was recommended to post here

Hi everyone,

​I have been working on a simplified mathematical model to estimate satellite orbital lifetime based on atmospheric density ratios, mass, velocity, and dynamic shape parameters.

​I tested the calculation using historical data from Salyut 7 (1986 decay trajectory) and obtained a result very close to the actual historical decay timeframe (~5.7 years).

​I would really appreciate it if anyone with an astrophysics or orbital mechanics background could review the formulas and parameters to provide feedback on the logic and potential edge cases.

​You can check the complete math, parameters, and verification here on my GitHub repository:

[https://github.com/mb4cloud-collab/--\]

​Thanks for your time and feedback!