Wikipedia:Featured picture candidates/newton

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[edit] Newtons cradle

Original - An animation of Newton's cradle

Alternative - Edited in response to concerns about the second ball leaving the group before the first ball strikes. If the time still needs to be increased, the frames which show the cradle in its rest position are 1 and 19 (current time for these two frames is .05 seconds).

Reason: It's Enc. value Nicely done animation.
Articles this image appears in: Newton's cradle
Creator: DemonDeLuxe

Support as nominator - Milk's Favorite Cookie 14:15, 15 March 2008 (UTC)
Comment. Previous nomination here. Pstuart84 Talk 16:11, 15 March 2008 (UTC)
Oppose Original, Support Alternative Why does the last ball seem to start moving away before the first ball has impacted the line? It needs more frames. Mfield (talk) 14:43, 15 March 2008 (UTC)
Oppose -Yes, I agree. It does need more frames. Rj1020 (talk) 17:14, 15 March 2008 (UTC)
Weak oppose per above. Would support one with higher amount of frames. crassic!^[talk] 18:25, 15 March 2008 (UTC)
- Support alternative. crassic!^[talk] 04:22, 16 March 2008 (UTC)
Oppose. This is unencyclopedic - a Newton's Cradle does not keep going ad infinitum; it dissipates energy to noise, heat, etc. and eventually stops. Pstuart84 Talk 19:19, 15 March 2008 (UTC)
Strong support - I can't understand the objections, this is one of the very best available animations, including the featured ones! It is realistic, stylish and sophisticated, adding considerable value to the article. I particularly like the excellent taste detail of the "Principia" under the cradle -- Alvesgaspar —Preceding unsigned comment added by 80.172.45.104 (talk) 22:00, 15 March 2008 (UTC)
- Because I think that if you'd never seen a Newtons cradle for real and you watched this animation, you'd be forgiven for not understanding that the ball striking the line is what causes the end ball to swing away, The missing frames make the end ball appear to leave before the first one has made contact. If I just saw this, I would guess there was magnetism involved. Does it not look like that to you if you put aside previous knowledge of what is happening? Mfield (talk) 22:10, 15 March 2008 (UTC)
- Yes, I agree it is not perfect, a longer pause after the ball strikes the line should be enough to solve the problem. And I would be the first to suggest it to the author if he were available. But I honestly think it is a minor flaw (maybe easly corrected by someone here?)-- Alvesgaspar (talk) 23:47, 15 March 2008 (UTC)
  - How do you address my objection? This depiction of the balls swinging endlessly is simply incorrect. Pstuart84 Talk 00:21, 16 March 2008 (UTC)
    - Nobody is likely to continue watching this animation for the length of time necessary for this to be any real issue, apart from the already hypnotic effect that this image has. scetoaux ^{(talk) (My contributions.)} 03:01, 16 March 2008 (UTC)
Strong Support - I voted for this on the 2007 POTY and im gonna vote for it now too, cos its top notch and its simple and easy to understand --Hadseys Chat_Contribs 01:04, 16 March 2008 (UTC)
Strong Support - Image is very tastefully done, good quality, except for the issue with the ball leaving before the other strikes. I'm going to see if I can apply my very limited skills in Imageready and make it look more realistic. scetoaux ^{(talk) (My contributions.)} 03:01, 16 March 2008 (UTC)
- Done. scetoaux ^{(talk) (My contributions.)} 03:40, 16 March 2008 (UTC)

Well done that's what it needed, I'm supporting this new version, changed vote above Mfield (talk) 03:46, 16 March 2008 (UTC)

Support Alt. per above--CPacker (talk) 04:39, 16 March 2008 (UTC)
Strong Support - alternative - very well done. diego_pmc (talk) 09:54, 16 March 2008 (UTC)
Oppose. Egad! A perpetual motion machine! Shouldn't the balls bounce to lower maximum heights in each cycle? Spikebrennan (talk) 13:34, 17 March 2008 (UTC)
- That would be very difficult to accomplish without having the original computer animation, and without making the GIF file much larger (because of added frames). — scetoaux ^{(talk) (My contributions.)} 19:11, 17 March 2008 (UTC)
  - That's not a great reason to make an unencyclopedic animation featured. Pstuart84 Talk 19:40, 17 March 2008 (UTC)
  - Then clearly the solution is to have a more explanatory image that exaggerates the decay rate (due to time/size constraints) but also explains within the image what is going on (either with a graph or equations). — BRIAN0918 • 2008-03-18 14:13Z
Oppose due to perpetual motion and background. Cacophony (talk) 19:51, 17 March 2008 (UTC)
Oppose per Pstuart84, Spikebrennan. Papa Lima Whiskey (talk) 02:26, 18 March 2008 (UTC)
Support I wouldn't recommend that this be put in the article on Conservation of energy but it serves it's purpose to clearly and accurately depict how a Newtons cradle works in an encyclopedic matter, the whole perpetual motion issue is inconsequential when it comes to whether this is encyclopedic or not and adding the extra frames to show loss of energy would just make the animation larger in size without contributing much in how the image is currently used encyclopedically. Cat-five - talk 03:11, 18 March 2008 (UTC)
- It really doesn't "accurately depict how a Newtons cradle works in an encyclopedic matter". In fact, it's inaccurate for the reasons I give above. Pstuart84 Talk 20:41, 18 March 2008 (UTC)
  - I wonder if a video of the real thing would be a good enc illustration of the phenomenon. Maybe not. IMO, the important concept to be illustrated here is the transmission of the momentum, rather than the friction damping of the motion. -- Alvesgaspar (talk) 21:33, 18 March 2008 (UTC)
Comment. A quick 'back of the envelope' calculation suggests that this contraption (in the favoured Alternative version) is almost a metre tall, and the book below it would therefore be around two metres wide. If correct, this would be another slight parting with reality, as this is considerably bigger than typical Newton's Cradles which are about 15cm in height. Anyone want to check and see what figures they come up with? --jjron (talk) 05:38, 19 March 2008 (UTC)
- Much more than that, if we assume the "small oscilations" linear approximation. For a period of 3 s, the length of the pendulum should be more than 2m [L = g.T**2/(4*pi**2) ]! Did I make a mistake somewhere? This is a good way to make my point that a "realistic" animation is not very illustrative as it is too fast -- Alvesgaspar (talk) 19:47, 19 March 2008 (UTC)
  - It takes awhile for the wave or whatever to pass through the middle bearings right? And what is jjron calculating based on? The thing could be a meter high or a millimeter, without some reference for size it's impossible to tell.. :D\=< (talk) 03:49, 20 March 2008 (UTC)
    - Oh the amount of time it takes to fall, of course :D\=< (talk) 03:50, 20 March 2008 (UTC)
      - Yep, time. Actually that's probably a better way to do it, but I'm not sure where Alvesgaspar's 3s period comes from. I get a period of nearer to 1s, which gives length of pendulum ≈ 25cm, so the total height would be maybe around 30cm, which is somewhat more realistic. --jjron (talk) 07:44, 20 March 2008 (UTC)
      - The period is the time of a complete oscillation, not just the time of fall -- Alvesgaspar (talk) 08:15, 20 March 2008 (UTC)
      - I know that, but (at least on my computer) I get a period of about 1s (with a 'time of fall' of about 0.25s, which was the figure I used in my first calculation). Do these things animate differently on different systems? --jjron (talk) 05:30, 21 March 2008 (UTC)
        
        Well yeah that's what you plug into the formula, but the gravitational force is your "some reference for size" that I couldn't see earlier :D\=< (talk) 16:51, 20 March 2008 (UTC)
        
        Yes, of course all calculations have been done on the assumption this thing is happening on Earth with g = 9.8ms^-2. Also assuming the absence of friction, which seems to be fair enough since it's in perpetual motion ;-). --jjron (talk) 05:33, 21 March 2008 (UTC)
        
        I have to disagree with the above estimates. Using $T \approx 2\pi \sqrt\frac{\ell}{g}\,$ (see Pendulum), you get $\ell \approx \frac{9.8 T^2}{4\pi^2}$ . Taking the timing from the original GIF as 0.72s (there are 34 frames, all at 20ms except for two at 40ms), this gives $\ell \approx 0.0180$ m, or about 1.8cm. This won't be exact, as it assumes the maximum angle to the vertical is small, but it's fairly close. Time3000 (talk) 14:26, 21 March 2008 (UTC)
        
        But the time that really counts is the one we perceive when looking at the animation !... -- Alvesgaspar (talk) 18:05, 21 March 2008 (UTC)
        
        Agreed. --jjron (talk) 03:36, 22 March 2008 (UTC)
Support either. Excellent animation that contributes enormously to explaining the concept. That the speed is decreased and energy loss is neglected are both appropriate for this type of illustration, and contribute to clarity. (To :D\=<: Yes, it takes some time for the wave to travel – a very short time. The speed of sound in stainless steel is about 5790 m/s, so if these are 1-cm balls the travel time is about 5 microseconds, obviously negligible.) --mglg_(talk) 21:21, 20 March 2008 (UTC)
Reluctant Strong oppose per perpetual motion concerns, but suggest it might qualify as encyclopedic under the GIF article as an illustration of GIF's animation potential. Reluctant because it is a very nice bit of work. Matt Deres (talk) 16:34, 21 March 2008 (UTC)