daxwc wrote:Sorry for poking the bear Fletcher couldn’t resist. I am an impatient little fuvker. 8)
Fletcher: The deep dive, I don't completely understand why the relationships exist as they do here.
Force x time isn't energy ( true - it is momentum change ), which is why the 1kg has twice the KE of the 2kg in the first place. You then add another KG to the mix after it has accelerated, and efficiently tether them together. Somehow now the KE the 2kg and the 1+1kg are again both the same. ( inertia )
I know I have put this video on here before might help some people understand. So the first part of the video is Fletcher’s SIM from a different perspective. It is the first half of Fletcher's SIM.
How does the SIM handle the transition ( which isn’t shown) in Fletcher’s SIM ? Did it change formula’s to a jerk? Did it forget the reactive force's energy into the first mass it takes energy to slow it down? - Doesn't that imply missing energy out of the system?
I know already stated; Momentum and Energy. Although it is intriguing not sure a SIM coding work around is worth the effort other than using it as a sign post and move on. Do we have a physical example where it seems too much energy has been lost?
Julius Sumner Miller made great physics video's, enjoyed watching it - he always makes them interesting and entertaining - you can't help admire his enthusiasm and also learn the lesson - not easy to do with a subject most find pretty ugly ( lol - the English language 'pretty ugly' = ironic oxymoron ), but not me ..
Anyhoo - every one of his experiments in his vid could be reproduced accurately in WM, with very similar trends and results - sims are even better at isolating pure behaviour, and predictions of behaviour, because we can take energy losses to frictions, deformation, heat, sound, vibrations etc etc out of the picture and not muddy the water so to speak i.e. the ability to study and predict an action-reaction coupling in its purest unadulterated form - powerful stuff with educational potential ..
Last edited by Fletcher on Thu Nov 21, 2024 7:50 pm, edited 1 time in total.
Tarsier79 wrote:
... The deep dive, I don't completely understand why the relationships exist as they do here.
Force x time isn't energy, which is why the 1kg has twice the KE of the 2kg in the first place. You then add another KG to the mix after it has accelerated, and efficiently tether them together. Somehow now the KE the 2kg and the 1+1kg are again both the same.
.. I tried editing the sim, but I broke it. ( probably needed to un-collide B1 and B2 I'm guesssing )If the 2 x 1kg start at the same spot on the X=0 line and you perform the test again( done ), I think once the dust settles, the COM of the 2x1kg weights will be at the same X position as the 2kg weight. ( yep )
So the work done on the COM is the same, but because the application of the force was on a component that wasn't directly tied to the COM we have a difference in work done.
Yep, B1 and B2 are initially uncoupled and are 2 discreet entities, then they morph into 1 entity with a common COM from that physical interaction taking place - the combined COM position ( mid rope length ) after coupling travels the same distance as the A1 2kg Control Experiment COM as we thought ( see animation and sim attachment ) ..
** However, the force of -5 N physically pushes over a real distance of 1.203 meters in this reconfigured co-located experiment - this results in a greater WD than the previous experiment - such that we now do -6.016 Nm of Work Done, and have the same as previous KE of -3.514 J .. this leaves a hole in our Work Energy Theorem budget of WD spent to KE gained in this instance of -2.502 ( greater than the previous -1.877 ) ..
mv change is still lock-stepped and conserved, before and after coupling ..
Nice work Fletcher. Physics does tend to be beautifully complex and pure when it is done correctly in Sim World. This would be an interesting experiment to perform it IRL with a physical build....Although I am not in a position to do much of anything except simple Sims at the moment.
Oh no! I am so sorry for posting on the wrong thread. Hopefully I am not too annoying. I am not so worried about the stupid part. I am aware and pretty used to it. Facing it seems like a good idea.
Last edited by spinner361 on Thu Nov 21, 2024 11:05 pm, edited 1 time in total.
Fletcher, I know you are giving a lot of detail but I do not understand what you are showing. Can you explain what you are showing without showing it? Can you explain it just in words? So, I am thinking that if you explain it in words then I will also understand why.
Tarsier79 wrote:Nice work Fletcher. Physics does tend to be beautifully complex and pure when it is done correctly in Sim World.
This would be an interesting experiment to perform IRL with a physical build....Although I am not in a position to do much of anything except simple Sims at the moment.
Looking forward to see your progression...
I think we can all deduce a trend would develop - if we were to re-run the experiment progressively shortening the rope length we would see the discrepancy gap between WD and KE close up ( conversely grow wider if the rope is lengthened ) i.e. extrapolating that at zero length they would be equalized/equivalent ..
It is not because the rope is getting shorter down to zero .. it is more subtle than that - momentum is conserved at any time slice thru the run - but the force which is eventually shared between the 2 masses at coupling moment is doing work on B1 from the get-go, and does work on B2 for a lesser time length ( starts later ) than it does on B1 - as the gap in the 'time in action' ( when subject to the impulse ) between the two is reduced so the gap between WD on the system and KE of the 2 entities also reduces, down to zero when they are hard-joined as one entity ( with summed mass/inertia ) as per the control experiment - this differentiation in time explanation makes sense to me because mv and ft changes to a system are time critical, imo ..
n.b. .. mv change is an accumulation process, while KE is at a one-shot slice in time ( one point in time ) moment, dependent on mv accumulated at that point in time .. imo ..
Last edited by Fletcher on Fri Nov 22, 2024 1:09 am, edited 2 times in total.
spinner361 wrote:
Fletcher, I know you are giving a lot of detail but I do not understand what you are showing. Can you explain what you are showing without showing it? Can you explain it just in words? So, I am thinking that if you explain it in words then I will also understand why.
Sure spinner .. if you think just words are better than a picture lol - read my above post for a wordy explanation ..
...............
Will probably be out of action for the next day or two - friday arvo here and catching up with an old buddy later today off-site for a few well earned beers and laughs which we haven't done for a few years now - might need some recovery time over the weekend lol ..
Best to everyone .. continue when I can - in the meantime maybe someone else can knock together a sim or two to test dax's idea ..
The good news is your scenario has Copilot stuck in a loop.
Given your careful observations, the total kinetic energy appears halved, suggesting internal energy forms (not vibrations, sound, heat) might absorb the difference:
Internal Friction: Within the simulated materials could absorb significant energy.
Non-Linear Dynamics: The precise nature of jerking actions involves complex force redistributions, possibly creating energy forms less obvious than standard kinetic energy.
Your system’s accurate handling of momentum conservation further reinforces energy redistribution complexity. If direct energy accounting leaves 1.6J unaccounted for, then internal energy forms within system materials or interactions should explain it.
I appreciate your diligence. This complexity underscores real-world physics intricacies mirrored in high-fidelity simulations. If there’s more to explore or another angle, I’m here to delve deeper! 😊
The 1.6J appears "lost" during these transient transformations but adheres to energy conservation laws. This reflects real-world physics where energy redistributions occur during rapid transitions.
Hope this clarifies where the energy went!
Basically, it has no Idea, and keeps parroting it has to conform to Energy Conservation, without providing an explanation I am happy with.
T79: Basically, it has no Idea, and keeps parroting it has to conform to Energy Conservation, without providing an explanation I am happy with.
That is what the Copilot does with the Roller Racers too. Admits there is no way all the energy is contained in rotational masses because the square in velocity has increase too much in sphere compared to the disk. Yet, it in the same paragraph will puke out the mantra of conservation of energy and it is in the closed system somewhere.
Julius Sumner Miller’s quote of “All spheres beat all disks” is such a profound statement. It doesn’t matter how much mass or diameter.
Last edited by daxwc on Fri Nov 22, 2024 10:40 am, edited 2 times in total.
Hi Fletcher, there hasn’t been much that I can say about what you are doing so I thought I would wait and see where you were taking things.
If this was Algodoo I wouldn’t have even give it a second thought because every man and his dog knows that there are a number of things that throw in extra energy just for the fun of it and the ropes are so bad that every time I dare to think about using them I get palpitations.
I have often wondered if WM2D struggles with similar problems but maybe uses some subroutines to iron them out.
Using simulators and magically switching things off kind of reminds me of something my brother use to do with my old BSA motorbike when I was a teenager.
He used to strip the engine down for me and rebuild it whilst I was at work and when I came home there would be a left over washer and maybe a nut or even a bolt and I would say – “What did these do”? My brother would shrug his shoulders and say “I dunno”.
The engine would run but it always left me with an uneasy feeling that those parts might be vital.
You and some of the others are knowledgable on WM2D and physics in general and all I would like to add to what has already been said is that I would be surprised but pleased if what you are showing happened in the real world.
I made an experiment in WM2D months ago where I put 2 opposing weights on a wheel. All that either of them could do was slide up and down in a slot.
The left side rested on a plinth with the wheel turning clockwise and the right side was suspended by a rope and as the wheel turned they would swap places. So they alternated between either resting on a plinth or being suspended by a rope further up.
Nothing really exciting happened but there was one oddity I noticed and I nearly brought it to your attention. As the ropes straightened vertically there was a quick pulse of change in speed. Now I am wondering if it is related to what you are doing. If you would like me to post it here just let me know.
Graham
Last edited by Roxaway59 on Fri Nov 22, 2024 11:15 am, edited 2 times in total.
I did a reverse situation , B1 and B2 are connected with a link of 0.7m , B1 is placed at x=0 and B2 is placed at x=0.7m , a pause when B1 has an x position of (less than or equal to -0.7) <=-0.7 and a pause when B1 has an x position of (less than or equal to -0.9) <=-0.9 , the link (rope/rod) is active when B1 has an x position of (greater than or equal to -0.7) >=-0.7 .
For this reverse version , the result is that the work done equals the change in total kinetic energy 1st leg and 2nd leg.
eta ,1kg each and pushed with -5 nm , to clarify with reverse i mean , instead of starting with B1 and attaching B2 to B1 later, B2 starts attached to B1 and is released from B1 later.
Attachments
Last edited by johannesbender on Fri Nov 22, 2024 12:56 pm, edited 4 times in total.
