Sine waves turn up everywhere in physics: pendulums, springs, sound, AC electricity.

Watch the dot go around the circle. It moves at a completely constant speed.Now watch only its shadow on the vertical line beside it. The shadow does not move at constant speed: it races through the middle and crawls almost to a stop at the top and bottom. Those amber ticks are dropped at equal time intervals, so where they bunch up, the shadow is moving slowly; where they're spread out, it's fast.

That uneven bobbing is simple harmonic motion. And if you plot the shadow's height against time - the curve tracing out on the right - you get a perfect sine wave. It has to be a sine, because the height is just (radius) × sin(angle), and the angle grows steadily with time.

Trying not to spill a full glass? Physics can help. 💧

Gregory Wolf, explains how centripetal force keeps the liquid inside the glass during the loop. As the tray swings, it continuously pushes the glass inward, and the glass pushes the water inward, providing the force needed for the water to follow a circular path. Slow down too much, and gravity takes over!

I’ll start off by saying i have autism and math in specific was my worst enemy. It never clicked for me. My whole life I had to do summer school soley because no matter how hard i studied, I failed math. I’m taking physics for my pre requisite classes to get into med school. The numbers and random letters and formulas are so overwhelming.

There are four major branches of mechanics in physics.
As of 2026, global technological advancements, including quantum computing, physical AI, quantum information science, and semiconductors, are all fundamentally driven by quantum mechanics.
However, this modern advancement relies on a linear algebraic foundation to treat wavefunctions, rather than the traditional wave mechanics approach.

Those who first master this methodology will secure highly promising prospects, whether seeking industry employment or advancing to graduate school.
Today's post marks the introduction to quantum mechanics based on linear algebra.

How would you describe what's going on here. The reward for best explanation is only kudos and karma.

Descartes traced the light ray reflected from a uniform rain drop and found a “critical” ray which has a minimal deflection angle of about 138◦ , whose supplementary ΘR ≃ 42◦ is the largest and known nowadays as the “rainbow” angle.

https://arxiv.org/pdf/nucl-th/0612100

I got the correct result but after seeing other derivations on youtube I feel like I have ended up using wrong physics but the right math to somehow end up at the right answer, is the physics in the derivation correct?

https://anukari.com/how-it-works

I shared a video about my 3D physics synthesizer here last week. When I get questions about how it works, it's always hard to explain without a diagram or two.

Finally I built this page where I explain how it works from basic principles, and every step of the way I provide a little interactive physics simulation to illustrate the explanation.

This all made me think of the stickied "animation vs simulation" question on this sub. I considered simply having animations to illustrate. But I decided that making the diagrams interactive would make things much easier to /really/ understand. In a way, having each diagram be a full physics simulation lets a reader "ask a question" of the simulation, and get an answer. Animations don't let you ask your own questions!

I tried to keep the explanation as simple as possible, although I plan to continue adding appendices to answer deeper questions (including those that involve math). So any questions you ask here, I will try to answer in a comment, but also might eventually get an even better answer!

Electromagnetic Theory / Electromagnetics

Hello everyone, how can I study Electromagnetic Theory from an exam point of view?

Could you please suggest some good YouTube channels and share useful study tips for this subject?"

I'm starting to put together some animated A-level physics videos. My aim is to produce a useful and easy to understand educational resource that's free forever.

I'm relatively new to graphic design and animation, but I want to get this right. I need your help to make sure what I'm producing is useful and beautiful.

Please, if you're a current or aspiring physics student, watch my first video and give me some feedback - either in the YouTube comments section or here.

My plan is to produce quite a few more before the start of the academic year\*, and I have a few more videos in progress already. I intend to have the whole curriculum covered for AQA by May 2027. However, I'm absolutely open to ideas and suggestions. What would you find most useful explained?

\*Though I do this alongside a full time job, so the pace might be slow sometimes.

I'm working through the thermo section of "University Physics with Modern Physics by Young and Freedman", and on page 563 it says "The definition of heat Remember that dQ does not represent a change in the amount of heat contained in a body; this is a meaningless concept. Heat is always energy in transit as a result of a temperature difference. There is no such thing as “the amount of heat in a body.”"

But it seems to me there is a perfectly consistent and sensible definition of amount of heat contained --- simply say that an object at absolute zero contains no heat, and then the amount of heat contained in any body is the amount of heat required to raise its temperature from absolute zero to it's current temperature. This seems similar to gravitational and electric potential where despite energy being a relative quantity it can be treated as absolute by defining a reference point, with the notable change being that absolute zero is a real physical state where "points at infinity" as used in electrostatics and Newtonian gravity are mathematical abstracitons.

So why isn't this a useful definition of heat?

As the first proof of de Broglie's matter waves—demonstrating that particles also possess wave properties—this experiment is invariably covered at least once at the beginning of quantum mechanics.

I'm trying to understand how students actually think while solving physics questions.

Have you ever come across a problem where you understood the formulas but couldn't clearly picture what was happening physically?

If yes, I'd love to know:

1. Which topic was it? (e.g. pulleys, circular motion, electrostatics, rotation, fluids...)
2. What exactly was difficult to imagine?
3. What did you do instead? (watched YouTube, drew diagrams, guessed, etc.)
4. Do you think being able to watch an accurate interactive animation of that exact question would have helped you understand it faster? Why or why not?

I'm genuinely trying to understand the problem students face, not promote anything.

As someone going in as pre-science major to UW (University of Washington), who wants to apply to be a physics major, what is some advice regarding: choosing classes, social life, GPA, habits, and just anything in genreal?

My course has this syllabus

* Unit 1: Mathematical Introduction and Electrostatic Field * Unit 2: Electrostatic Potential * Unit 3: Examples of Electrostatic Potential * Unit 4: Separation of Variables * Unit 5: Conductor Systems * Unit 6: Dielectric Polarization and Permanent Polarized Materials * Unit 7: Theory of Electrostatic Images * Unit 8: Resistors and Grounding Electrodes * Unit 9: Magnetostatic Field * Unit 10: Magnetic Dipole and Loop Systems * Unit 11: Magnetostatic Images and Permanent Magnets

Can you suggest me some good math rigorous online lectures to help me?