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Wolphram jonny

 Discussion on question by LeoMurillo:…

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Wolphram jonny
Jan 30 04:50
No way to tell with just two points it could be any!
Wolphram jonny
Jan 30 04:50
yes, if you have extra forces the particle can move along any circle. In such a case you need at least three points, as there is an infinite number of circles on the sphere that include two specific points
Wolphram jonny
Jan 30 04:50
you also need to know how many turns the particle has completed between the two measurements
 

 Discussion on question by tenebris in…

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Wolphram jonny
Dec 7, 2024 22:58
Do you think this is the right place for your post? May be it is you who doesn't know what physics is, your post is about sociology.
Wolphram jonny
Dec 7, 2024 22:58
Well, if you acted in those sites like you acted here, with disregard to others by posting a question that is not about physics, I can see why they would be annoyed by you.
 

 Discussion on question by Christian: …

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Wolphram jonny
Sep 11, 2021 21:58
$F=-GmM/d^2$ ...
 

 Discussion on question by John: Newto…

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Wolphram jonny
Jul 24, 2021 23:19
You are right, got it. Brace for the Nobel prize!
Wolphram jonny
Jul 24, 2021 23:19
and you are just adding forces acting on every particle in the object. there nothing wrong with that. they are acting on different particles that belong to the object
Wolphram jonny
Jul 24, 2021 23:19
the center of mass of the rocket plus the propellant released into space does not accelerate (assuming the propellant does not interact with the environment). Regarding the other point: exactly, that is why internal forces doe not move the object, because action-reaction pairs cancel each other. The short reason is what you said, the proof is in the link
Wolphram jonny
Jul 24, 2021 23:19
what other forces are acting over the body other than action-reaction pairs?
Wolphram jonny
Jul 24, 2021 23:19
then why you say it is wrong to consider only those forces?
Wolphram jonny
Jul 24, 2021 23:19
you seem to suggest that not all of these forces should be included?
Wolphram jonny
Jul 24, 2021 23:19
I dont need to ask him, his answer is pretty clear
Wolphram jonny
Jul 24, 2021 23:19
I am starting to suspect that you have not learn math or physics beyond high school, am I right? I m not asking to scold you, but to see why we fail to understand each other
Wolphram jonny
Jul 24, 2021 23:19
"the net force due to internal forces is attributed just to the action forces" that does not make sense to me. Where in the demonstration did he assume that?
Wolphram jonny
Jul 24, 2021 23:19
a rocket is an open system, particles leave the rocket. it does not apply here
Wolphram jonny
Jul 24, 2021 23:19
you will have a better understanding if you read the link I posted, do not rely on Dale's short version
Wolphram jonny
Jul 24, 2021 23:19
I dont really understand what you mean about the action being what moves the CM. What action force? but the link that I sent you does address your question, it is shown that the velocity of the center of mass is a constant if there are no external forces. That means the body will not accelerate. What step you do not understand? the demonstration does not assume that the forces are on the same line, only that $F_{21}=-F_{12}$
Wolphram jonny
Jul 24, 2021 23:19
This should help you, you can skip the irrelevant parts. link.springer.com/chapter/10.1007/978-3-030-15195-9_6 you want to understand 6.3.7 (note: a rigid body is just an instance of a system of particles)
Wolphram jonny
Jul 24, 2021 23:19
get a book on general physics 101, it can be shown that the center of mass does not accelerate due to internal forces. The proof is the same as Dale's answer, but with a little more detail. It is not something that is unclear. Thus the answer is no, it will not accelerate if the third law is correct, even if forces were not on the same line.
Wolphram jonny
Jul 24, 2021 23:19
I am not sure how your conservation of momentum (2) looks like, if an object could accelerate spontaneously then momentum would clearly not be conserved.
 

 Discussion on question by Deschele Sc…

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Wolphram jonny
Jun 1, 2021 11:43
I see, thanks..
Wolphram jonny
Jun 1, 2021 11:43
I am not an expert, I just remembered that
Wolphram jonny
Jun 1, 2021 11:43
But a single photon can have any energy density you want by boosting yourself, so it cannot form a black hole
 

 Discussion on question by porton: Are…

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Wolphram jonny
May 31, 2021 22:29
my fault!......
Wolphram jonny
May 31, 2021 22:29
was not that your assumption? that you have a solution of an NP hard to compute wave function? I might have misunderstood your issue
Wolphram jonny
May 31, 2021 22:29
well, you will have a solution to an NP problem then. but the fact that it is a QM system is irrelevant.
Wolphram jonny
May 31, 2021 22:29
If the state has an analytic solution, then it is not NP. You can have a system to be complex enough to be NP, but in such case you will not be able to compute the general solution
 

 Discussion on question by Alex: The p…

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Wolphram jonny
Jan 6, 2021 04:53
But there is no difference mathematically, you can consider the time to "flow" or to exist all simultaneously. That is a philosophical issue not a physics one, because there is no change in the predictions from the equations, regardless of your flawed arguments.
Wolphram jonny
Jan 6, 2021 04:53
no, what gives cause an effect is the evolution of the system. The evolution is not random, if follows hyperbolic PDE's that generate an evolving structure that is optimal in 3+1 spacetime
 

 Discussion on answer by Wolphram jonn…

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Wolphram jonny
Nov 17, 2020 15:31
I think we are speaking different languages here. Let me read this again tomorrow
Wolphram jonny
Nov 17, 2020 15:31
@mmeent you got it all wrong
Wolphram jonny
Nov 17, 2020 15:31
@mmeent they have contravariant indexes and contract with the covariant ones. if s^2 is a second rank tensor, where are the indexes?
Wolphram jonny
Nov 17, 2020 15:31
are you just troling me?
Wolphram jonny
Nov 17, 2020 15:31
@mmeent it is not, the indexes are contracted! do you know anything about the subject?
Wolphram jonny
Nov 17, 2020 15:31
in curved spacetime light moves locally at c
Wolphram jonny
Nov 17, 2020 15:31
@mmeent what is it then?
 

 A General Chat Room

This is a general discussion room. Here we chat about random ...
Wolphram jonny
Feb 23, 2020 18:17
Because I dd not answer your question. I was going to correct or rather add to the answer. Whait 5 minutos and I will correct it
 

 Discussion on question by sam wolfe: …

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Wolphram jonny
Feb 5, 2020 17:15
@Umaxo, yes, that is right
Wolphram jonny
Feb 5, 2020 17:15
I think that first you need to decide what is the definition of a non conservative force in the absence of a definition of work, and start from there (which I am not sure is possible). potential energy is also defined in terms of work, so the problem seems circular without using it.
Wolphram jonny
Feb 5, 2020 17:15
Oh sorry, i missed it!
Wolphram jonny
Feb 5, 2020 17:15
what about showing that in a closed trajectory the total work is not zero?
Wolphram jonny
Feb 5, 2020 17:15
you seem to have a mistake, you dotted one side of the 3rd equation with r dot and the other with r double dot
 

 Discussion on question by Jinny Ecckl…

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Wolphram jonny
Feb 1, 2020 17:35
per area of the set will be the same than the original, but the area will be the entire sky. And you still have more stars behind those same stars that also contribute , making the total glow infinite
Wolphram jonny
Feb 1, 2020 17:35
that is incorrect, see PM 2Ring comment above, the brightness per visual area will not change (the total will because it will be farther away). So the effect of moving it away is only to change the visual area and total brightness, but the brightness per area will remain a constant. Now, sum an unlimited number of stars and the susrface brightness
Wolphram jonny
Jan 31, 2020 19:45
chose one of the steps in the deduction of the paradox and point why it is wrongs
Wolphram jonny
Jan 31, 2020 05:11
Now, keep adding infinite stars on each direction, and the sky will glow infinitely
Wolphram jonny
Jan 31, 2020 05:10
but if the universe is infinite you will have a star in every direction, so the total area will be the sky. So the luminance of the sky per area must be as bright as that of a star.
Wolphram jonny
Jan 31, 2020 05:09
once the star is very far away, the area will be so low that the total luminance will be low too. You might get a photon every million years
Wolphram jonny
Jan 31, 2020 05:07
as the star gets farther away, the visual area diminishes but the luminance per unit area does not