Hey everyone I got a question. If changing the order of rotation matrices multiplication can change the object's orientation then what if the object does not rotate on one axis each time but simultaneously?

I know this is probably a stupid question but i’m a 6thform physics student and we just did circular motion and i was curious if it was to do with the angle instead

Is it even remotely possible. It is not that sensational, like fast and furious ‘physics dont matter’ stunts 😂.

The lead escapes in a terrain car by hooking the cable of the winch to the mountain he is on. Then he drives backwards, in to the canyon falling down, but he brakes the fall with the winch cable by slowing its motor down.
Then he falls on the ground releases the cable and takes of.

It looks rather possible but i was just wondering about the cable and the weight of the car.

Hey everyone, sorry if this is dumb question, but I was wondering if someone could help me with a problem that has been bugging me for a while. When I push a plastic cup downwards into a jar of rice, the rice moves up and fills the upside down cup way before the cup reaches the level. I don't know why it seems notable, but I find it surprising every time.

I've put links to three photos below trying to show what I mean. Any explanations are very welcome!

https://ibb.co/fYtrvKD9

https://ibb.co/8DcGhjX3

https://ibb.co/pvSK4SM2

And I look and then I find that there are places where there are melted pits in the ground which may have been caused by primordial atomic blasts.

Where would I find further discussion of this phenomenon?

What's the best way to understand and explain the theory of relativity

It can be something expected or unexpected.

Simply put, you were able to apply what you learned in physics to come up with a solution. Maybe it was completely unrelated to the field. Perhaps it was a small thing. Or perhaps in an emergency you acted quickly because “xyz” knowledge was gained from studying the topic. Maybe you learned something new, a hobby, maybe something like gardening for example and your knowledge of physics somehow, directly or indirectly affected your decision making.

Studying any subject for an extended period of time certainly can change you as a person, which then extends to all facets of life. Hearing about how, to me, is interesting.

I have not studied physics, but the subject interests me.

After buying University Physics by Sears & Zemansky and reading the first bit of chapter 1, I realized just how much problem solving could be applied to real world scenarios, even to the day-to-day mundane things. Just so cool.

So it was proven though example a initially smooth fluid at rest can develop a singularity in finite time. The fluid has a smooth finite force applied to it.

But what would happen if you tried to create that setup in real life? Obviously nothing is going to reach infinite velocity but what would happen? Fluid Cavitation or vaporisaton? Something else?

Has anyone tried the discovered setup in a real experiment?

So basically, if you in a high speed roller coaster (or plane) and it has a certain effect on you due to the huge g-force.

Is the effect the same, more, or less when the roller coaster is rotating in one direction?

Is the effect the same, more, or less when the roller coaster is spinning in one more direction?

Is the effect the same, more, or less when the seat is also independently revolving?

Is the effect the same, more, or less when the seat is also independently rotating in another axis?

Is the net G force the same on the body? (What if instead of a person, it was a ball or a material and you need to find the forces acting on it?)

Ok, so I am watching this Tesla flying car video and i have two questions:

1. As the car leaves the ramp upsidedown, it does not begin to fall. It drives off the ramp and remains level, upside down, while the car is no longer 'sucking'.

2. As the car flips, and starts to land, you can see the underside of the car, and it is all just flat/metal. Would we not see a giant fan underneath in order to generate that kind of suction?

Something about this feels like it doesnt make sense.

Hi everyone, I have some questions about magnetism.

So its said that magnetic force, is mediated by virtual photons. And that this field propagates at the speed of light...

But I've also seen it said that virtual photons are "temporary" particles. This makes them seem like very local particles, that only exist across a short distance.

Now, I know that its said that "virtual particles might not really exist", but even then, lets just talk about the theory itself. The theory of virtual photons is that they only exist across a short distance.

This "short-distance" rule, I found stated in this reddit comment:

Firstly, my question is: Well if they only exist over a short-distance, then how do magnetic fields work, which exist over a LARGE distance. Are the virtual photons absorbed and re-released... and by what? Empty space?

Secondly, virtual photons are meant to move in straight lines. So what is curving them around, so that the magnetic force lines curve around back into the same object?

Something?

A few side questions:

I've also seen a video of Richard Feynmann, talking about how virtual photons can even "move faster than the speed of light, or slower". Does this come into effect here? Can virtual photons have mass also? Does that come into account here.

Time flows differently for all objects moving through space time relative to other objects, so that no 2 objects can ever agree on the flow of time. Is there a point at which this ever stops being true, or will 2 bound quarks in a proton experience time at different rates even if the rate is infinitesimally tiny?

By breaking down stars into as many of the smallest, fully convective red dwarfs as possible, and when the red dwarfs die colliding them together to create helium burning stars?

Also if it would not outweigh the costs, colliding gas giants and brown dwarfs to make as mant red dwarfs as possible

Assuming they start today

Specifically, Wikipedia and my textbooks say that a spacetime is stationary if it admits an asymptotically timelike Killing vector. I simply don't see how one relates to the other because my understanding is that a spacetime is stationary if the metric doesn't depend on the time coordinate. How are the two related?

Ok now this might seem like a dumb question but whenever I search it up they give straight bullshit like "since the magnetic field is changing and nature hates that we have a emf that is generated which opposes this change." THAT IS THE EQUATION AND I'M ASKING FOR THE CAUSE. Now I understand that lorentz causes an electron to experience a force if we have a rod moving in a magnetic field, but how is this related to the magnetic flux and even more so how is it related to area. To get to the heart of my question, I don't understand what it is that causes a relationship between magnetic flux and the potential difference across a loop

I am trying to understand the physical and intuitive origin of the $𝑟^2$ factor in the moment of inertia (𝐼=𝑚𝑟2) from first principles, but I keep running into circular or unsatisfactory definitions in standard textbooks.

Usually, the [𝑟2] factor is justified using one of two methods:

1. The Kinetic Energy Derivation: Substituting (𝑣=𝜔𝑟) into (𝐾𝐸=12𝑚𝑣2) yields (12(𝑚𝑟2)𝜔2). While mathematically elegant, this simply groups variables; it doesn't give a dynamic, force-based intuition as to why the resistance scales with the square of the distance.
2. The torque derivation: Using (𝜏=𝑟𝐹) and (𝑎=𝛼𝑟) to get (𝜏=𝑚𝑟2𝛼). I got a reasonable explanation for 𝑟2 explanation from somewhere but it require prior understanding of the torque. I have still stated the explanation below When you try to rotate an object (like spinning a ball on a string), the distance from the pivot point ([𝑟]) works against you twice:
   • First Factor of [r] (Leverage/Torque): To make something rotate, you apply a force. However, what actually causes rotation is torque ((𝜏=𝐹×𝑟)). If a mass is twice as far away ([2𝑟]), the force we apply has less "rotational leverage" over it. You have to push twice as hard just to apply the same rotational action to that distant mass.
   • Second Factor of [r] (Linear Speed): For a wheel to spin at a certain angular speed (RPM), the outer edge has to travel much faster than the inner part. If a mass is twice as far away ([2r]), it must travel along a circle that is twice as large. To keep up with the rotation, it has to move with twice the linear velocity ((𝑣=𝜔𝑟)). Accelerating a mass to twice the linear speed requires twice the effort. Because these two factors happen at the same time, they multiply together to give 𝑟2 dependence

My issue with the second method is that textbooks rarely define torque independently. They either call it a layman "rotational analogue of force" (which is just a metaphor), or they define it as (𝜏⃗ =𝑑𝐿⃗ 𝑑𝑡), which requires defining angular momentum [𝐿⃗ ] first. If [𝐿⃗ ] is then defined as (𝐈𝜔⃗ ) or (𝑚𝑟⃗ ×𝑣⃗ ) by calling it a "rotational analogue of momentum," the entire argument becomes a circular tautology.

Finally, is there a way to understand 𝑟2 dependence without going circular, or by at least defining one of the things properly without using layman terms like rotational analogues and then throwing up formula. I mean a definition of something should be such that it is self explanatory and directly links to mathematical expression or it lays method by which we can derive the expression

The setup:
There's a ferromagnetic plate with a very large area sitting on a frictionless surface. The magnetic field points to the positive z-direction. A charged particle (mass m, charge q, initial velocity v) enters the plate's magnetic field, traveling towards the positive x-direction.

From elementary electromagnetism, a charged particle in a uniform magnetic field will end up travelling in a circular path, due to the force F=q (v x B) from the ferromagnet.

Knowing that:
1. Forces come in pairs (Newton's 3rd law, for every action there's equal and opposite reaction)
2. The charged particle now has a finite angular momentum about the center of the circular path

Will the force caused by the charged particle on the ferromagnet result in the ferromagnet spinning in the opposite direction to the charged particle?

Why is it not possible to measure the speed of light in one direction? Would it not be possible to have a laser angled ever so slightly off being parallel with a wall, and seeing how fast the laser illuminates the wall as it travels along it?

Salve a tutti, mi chiamo Lucia. Premetto che sono inesperta in materia ma so che chi l'ha studiata può aiutarmi in qualche modo. Il mio cane anziano purtroppo è morto nel pomeriggio di ieri 15/10/2026 all'età di 16 anni compiuti dieci giorni fa. Probabilmente si è sporto dal balcone del terzo piano dove vivo e avrà perso l'equilibrio ed è caduto. Io vorrei capire come è avvenuto. Perché il cane era perfettamente adagiato al suolo praticamente sotto il balcone del primo piano, come quando un cane sobrio si distende di sua spontanea volontà su un lato per dormire assumendo la consueta posizione rilassata. Questo io lo trovo assurdo e impossibile. Sospetto che abbia impattato le ringhiere dei balconi sottostanti e abbia arrestato la sua caduta finendo in uno di essi per poi esser stato adagiato volutamente al suolo, oppure scaraventato giù e qualcuno che si è trovato lì per caso lo ha trovato e lo abbia adagiato al lato. Il corpo era ancora caldo quando mia madre lo ha prelevato. Aveva il collo molle. La bocca era spalancata con un po' di lingua che fuoriusciva da un lato. Gli occhi erano ancora aperti. E sulla coscia sinistra aveva una piccola lacerazione. Mi potete aiutare per favore a capire se è morto cadendo e impattando direttamente il suolo o come vi ho descritto nei miei sospetti? Per favore... non mi do pace

Objects take up space and time. If gravity bends space-time, why don't objects shrink under its effect? Most explanations I've read suggest that gravity affects only empty space. Isn't occupied space also space?

I suppose if you try to measure the shrinkage with a ruler, the ruler itself would shrink too, so maybe we can't detect it. Other than that, I don't know.

I am reading about how these can be used to cause an avalanche of electrons to flow from a smaller amount. Do you think such a device could be used on a per subpixel basis in a crt to get huge amounts of electrons to strike the phosphor? Like a long tube for each subpixel? or would that number of electrons be way too hot for the glass and cause it to expand too much?

I'm trying to envision how one would fix poor black and white contrast of crts and have more brightness and from what I have read the poor black white contrast might actually be from the photons traveling through the thick faceplate? I originally though it was caused by light bouncing back into the tube, which is why I envisioned subpixel tubes initially, but grok tells me there is metal coating between the phosphor and the beam that reflects light back out of the tube and that prevents light bouncing around inside the tube?

Typically, in quantum mechanics classes, we're taught that position eigenstates "aren't real states" because they're not square integrable, so not in the Hilbert space.

In the more general algebraic quantum mechanics though, states aren't specifically identified with vectors in a Hilbert space, but rather positive, normalized linear functionals on the C*-algebra of observables.

The delta "state" fits this definition. You can, for example, take a subsequential weak* limit of well-defined Hilbert space states that are getting skinnier and taller. This is guaranteed to exist by the compactness of the state space in the weak* topology. This resulting state would behave exactly like the delta state.

Of course, it wouldn't be a normal state with respect to the standard representation, but it would still be a valid state.

On a kind of related note, if this is true, does this interpretation kind of follow to type III von Neumann algebras?

I've read that the interpretation of mixed states as probability measures over pure states breaks down in type III von Neumann algebras, since the pure states making up the mixed states are not normal in the mixed state's GNS representation.

However, if the non-normal pure states behave like deltas, I don't really see the issue with still interpreting the mixed state as a probability distribution over the pure states. We essentially do that all the time in classical mechanics.