This man's treadmill has an exercise ball get sucked up under the treadmill when pressed into it from behind. The treads are rotating in the opposite direction the runner is moving, so if the ball slows the treads, the runner should be jolted FORWARD, right? But he is seen tripping/falling backward.

My best guess is that the motor is in a control loop with something that detects the speed of the treads. When the ball is causing friction, the speed of the treads decrease, causing the motor to increase its driving force to achieve a target speed. Then when the ball pops off, the motor stays at the higher driving force and the treads accelerate backward.

That doesn't explain why the motor would have had a harder time reducing power than increasing power. Perhaps when it was increasing driving power to overcome the friction of the ball, the runner was mid-air?

https://www.reddit.com/r/KidsAreFuckingStupid/s/EssXdfhc6C

Im trying to draw something accurately, and i want to know that, especially if you would be bigger in size, because pf less pressure on your bones/muscles.

why?

Especially recently, we hear a lot about AI (Fable in particular) solving/disproving longstanding mathematical conjectures semi-independently, whereas it doesn't seem to have nearly as much success in theoretical physics. Everyone's opinions is welcome (that is the goal of this post).

So we've got this module and on it, it says "an angle of 45° south of east" so Fx is positive and Fy is negative right? So Fx=Fcos(45°) and Fy=Fsin(-45°)? That is what I got based on my research but they are both negative on our modules, it shows Fx=Fcos(-45°) and Fy=Fsin(-45°). Which is right? I dont know why that happens, can someone explain?

So after learning a bit of physics beyond my syllabus I learnt that megnetic field creates an electric field. Now using my logic of electrostatics this electric field and basic electomagnetism, the negatively charged particles starts uniform circular motion that is perpendicular to the magnetic field (as the centipetal force that makes the uniform circular motion is perpendicular to the magnetic field). So due to this motion there is a polarisation of charge at the edge (Hall effect I guess) so as there is positive charge on one end and negative charge on the oppsoite end . Electric field in induced perpendicular to the magnetic field. Now if I am right this force is the reason for work done.

So my doubt is what is the magnitude of this force that the the force due to the electric field, I know it is qE but what exactly is the value of E over here?

Also is it due to what I explained over here that we conculde that magnetic field and electric field are perpendicular to each other. Also is my reasoning of circular motion causing the polarisation of charge correct?

Thanks to all of you for clearing this concept!

I see physicists talk about invariant or rest mass as a quantity which is intrinsic to a body or system and cannot change. But there is such a thing as mass defect which I calculated in chemistry class. So clearly in nuclear physics at least, mass of a system can change when the constituent massive bodies are combined in certain special ways. As for instance when an atom is created or destroyed. Mass is either gained or lost and you can directly measure this. So mass doesn't seem like an invariant property and can change in motionless bodies. So if this is the case, what exactly is meant by being "invariant"?

I'm trying to study scattering amplitudes, and there's a lot that I'm still trying to wrap my head around the math, but one thing that keeps confusing me is what I'm even calculating here. The concept of a scattering amplitude itself kind of eludes me.

See, I understand the state of particle to include information on probability. So, if you have the full knowledge of a particle's state, you also have full knowledge on the probability of finding it at any given position, at any given momentum, etc.. But I also understand the state to evolve deterministically. If you know what the state is at Time A, you can know what the state will be at Time B. Only measurement if probabilistic, that was hammered into me early on.

So when I hear "The chances of system evolving from one state to another", I really feel like I'm missing something. And I've seen scattering amplitudes described that way. So, what is this scattering amplitude that we're calculating?

Is Classical Mechanics about determining the future position of a system by studying its motion, or is it about determining the future state of the system. Like for a particle both the goals are equivalent, but when it comes to a system of particles they are not. So what is the ultimate goal of classical mechanics? To determine the state evolution of a physical system or its future motion. The reason for this doubt is that some books claim classical mechanics to be the study of motion bodies acted upon by forces, and some say it is a framework which lays the basis for all of physics, and its job is to figure out the future state of a system.

For my upcoming physics project I've decided to make a stirling engine

I am basing my design on a specific video design .

However, it seems I ran into a problem here. While watching the video, the person making the model used steel wool for the displacement piston but didn't specify which grade.

I asked gemini and it told me to use grade 3 or grade 4 steel wool. I'm a bit skeptical about it. I want to double check this with people who has some experience

Can anyone confirm me which grade would be best for this specific model? Also, this is my first time making this project. I would love to receive some tips and common mistakes to avoid while making this.

Also I am a student and this video is the one which I can make. I saw the rest of them and don't have the materials to make it nor do any shops near me sell those materials

Being that are the other theories like shortcut access to differnt part of space time or a time window into past present and future like shown in interstellar and the equation of space time fabric becoming infinite are all just human exaggeration, and fantasy just like we fantasise things about the egyptian pyramid like aliens built them, etc

Hello I am Just a layperson and do not know much about physics. I would be really thankful if somebody could explain this in simple Terms (If possible).

Ive seen several people talk about the theory that our universe is contained within a black hole from a previous parent universe, and I understand the general concept, but there are some questions Ive never heard answered.

1. If we are inside a black hole, shouldnt we see an increasing quantity of mass as the black hole consumes material from the parent universe? If the black hole isnt 'eating', wouldnt it shrink from Hawking radiation -- which violates the concept of universe expansion?

2. Are there theories about the black holes parent universe? If a black hole contained the mass of our universe, how much mass would be in the parent universe? Is the black hole the largest ever concieved, or would it be more proportional to ultramassives like ton 316. How large is the parent universe? Would being inside a black hole alter the fundamental scale of our universe? Are atoms smaller in the black hole than in the parent universe? If not, could we assume the size of the black hole is equivalent to the size of the universe? How big would that make the parent universe?

Kind of alot ik, if there is material on this Id love to read it.

Right now we have moon orbiting planet orbiting star

Has there ever been an example of more levels than that? Can it exist?

I can follow the math of how you derive the electric and magnetic fields from it okay, but I’m sometimes confused as to how a vector potential is the same kind of idea as a scalar potential.

So, scalar potential I have a philosophical intuition for. When a charge moves from an area of high potential to an area of low potential, this corresponds to a proportional change in potential energy (the change proportional to the potential drop and the amount of charge). The reason this works is because both potential and potential energy are scalar values.

When I hear about a vector potential, my mind imagines that a potential change therefore cannot correlate with a change in a scalar value (potential energy) and should instead correspond to a change in some vector quantity. As a charge moves from a position with (x,y,z) magnetic potential to a position with (x’,y’,z’) potential, then some vector quantity should also change. And obviously this can’t be potential energy because potential energy is a scalar.

So, assuming my reasoning here isn’t flawed, what is this vector analogue to potential energy? If there is none, for what reason am I wrong here? And how does this all apply to electromagnetic 4potential?

So I know there are a few things that can happen when a photon comes in contact with a substance.

one of which is thermal absorption.

what i am unclear on for this is what the exact mechanics of that is.

I am sure i am missing something but with scattering, reflecting, photoelectric all seem to be explanations of the conservation of energy other than the thermal absorption portion..

is the kinetic energy due to the electron cloud jumping up an energy level or when it drops back down or is it the retained difference or some other mechanic entirely.

If you look at Chladni patterns, it’s really interesting to see how chaos can turn into these very specific patterns.

Do we have a good idea of WHY though?

So I wanna do a research paper on Astrophysics, but my physics is not very advanced? Any advice for beginners??

I am starting my first year undergraduate in my high school I have done books like I.E irodov and some books from Indian and soviet authors (tho Partially) for mechanics should I go for jhon R taylor?

I’ve seen it said that any massless spin 2 boson would function identically to gravity. But would this boson necessarily use mass as its charge?

You spin faster at the equator right?
Which means the force of the earth spinning is stronger than the pull of gravity at the poles.

Should I move closer to the equator to lose some weight? Or should I try something else?

I'm a 12th grade student and the last lesson of physics ive had is back in 9th grade and my brain is completely genuinely fried. Any tips on how to survive and not fail physics? what should i try to study ahead to make it easier for me to absorb the lessons? thank you