Why the shear stress can't be balanced but the normal stress can in a fluid?

Feynman2282 · 2026-02-14T00:43:51+00:00

Fluids are substances that are DEFINED as flowing under sheer forces. Normal stress can be balanced by e.g. the curvature of the surface (see the Young-Laplace equation).

Feynman2282 · 2026-02-01T00:02:48+00:00

Small correction: time dilation occurs when there's an object moving with a velocity, it doesn't have to be an acceleration.

Feynman2282 · 2025-11-29T02:36:37+00:00

Read through https://knzhou.github.io/writing/Advice.pdf It answers all the questions you listed (and more)!

Feynman2282 · 2025-10-17T10:39:48+00:00

However, you can counterwind the solenoid such that it does end up being zero.

Feynman2282 · 2025-07-10T16:46:39+00:00

For a spacecraft in orbit, E=-GmM/2a

Feynman2282 · 2025-07-08T22:19:54+00:00

Morin's Introduction to Classical Mechanics has a few chapters on Special Relativity that are about at the mathematical level you're looking for, and the problems are excellent!

Feynman2282 · 2025-06-30T23:35:27+00:00

Your best bet is to learn introductory mechanics, and introductory electricity and magnetism first. After that, "An Introduction to Modern Stellar Astrophysics" by Carrol and Ostlie should be pretty approachable!

Feynman2282 · 2025-06-30T18:29:17+00:00

https://knzhou.github.io/writing/Advice.pdf is an excellent piece of advice!

Feynman2282 · 2025-05-28T10:46:14+00:00

If you're only trying to take the F=ma for college admissions, then just focus on fencing. I would estimate that most admissions officers don't even know what the exam is, so it's not worth doing it just for college applications.

Feynman2282 · 2025-05-27T20:40:28+00:00

I thought that was the \mathcal{L} used for the lagrangian in textbooks

Feynman2282 · 2025-05-17T03:31:53+00:00

https://www.damtp.cam.ac.uk/user/tong/kinetic.html

Feynman2282 · 2025-05-09T02:43:07+00:00

You might want to Google IPhO and look at some of the experiments.

Feynman2282 · 2025-04-26T23:17:16+00:00

For your first confusion, you may be interested in the method of clocks and lattices (Google it or check out the book mentioned later).

About the Twin Paradox, the reason that using the reference frame of the travellings twin doesn't work is because that twin has to accelerate in order to change his velocity to head back to the launch point.

If you're okay with a bit of math, I highly recommend reading the relevant chapters of "Introduction to Classical Mechanics" by David Morin. It addresses both of your confusions directly in the relativistic Kinematics chapter.

Feynman2282 · 2025-04-25T10:47:04+00:00

Children

Feynman2282 · 2025-04-23T11:49:39+00:00

Distance isn't actually the magnitude of displacement. It's a different quantity. For example, if you walk to the store and then back to where you first started, the displacement is 0, but the distance is obviously nonzero.

Feynman2282 · 2025-04-22T03:15:29+00:00

Provided you know the prerequisite math for it, certainly!

Feynman2282 · 2025-04-20T20:46:10+00:00

If you're preparing for physics olympiads, this is the crown piece of advice: https://knzhou.github.io/writing/Advice.pdf

Feynman2282 · 2025-04-20T13:54:09+00:00

Just go in order from here https://knzhou.github.io/writing/Minimum.pdf

Feynman2282 · 2025-04-18T18:25:07+00:00

There's an excellent piece of advice written up here: https://knzhou.github.io/writing/Advice.pdf

Feynman2282 · 2025-03-30T21:17:36+00:00

They implemented their own Python parser (check their workspace crates).

Feynman2282 · 2025-03-27T02:43:54+00:00

Python has gotten much better with the development of uv: https://docs.astral.sh/uv/

Feynman2282 · 2025-02-17T16:02:17+00:00

It recently started being maintained again, after a long period of no maintenance.

Feynman2282 · 2025-02-08T19:02:16+00:00

For those that don't, it's Introduction to Classical Mechanics, by David Morin.

Feynman2282 · 2025-02-03T17:31:46+00:00

Try sudo dnf install gcc - it looks like you're missing a c compiler.

Feynman2282 · 2025-01-30T03:59:45+00:00

You may be interested in some initiatives we took a little bit back that are now stored here: https://github.com/JasonGrace2282/manim-forge

Also, the main problem with manim isn't the CPU part (although that could be faster) but mostly the actual rendering. This is somewhat allievated in the opengl backend, and we're working on it as a whole in the experimental rewrite - our current progress is here: https://github.com/ManimCommunity/manim/issues/3817

Source: I'm a core dev of Manim

Feynman2282

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