ARFC_N_XXVIV_Results - Updated after Review

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ARFC_N_XXVIV_Results - Updated after Review

Postby V4nKw15h » Tue Oct 23, 2007 3:34 pm

Results - Updated

Light :lms:: 634 Dr Dillo
Dark :dms: 652 Hersmunch

After much controversy....

Congrats to Dr Dillo and Hersmunch. Only 4 people entered which is a little bit of a shame.

I enjoyed seeing all the entries though, so thanks go to all who participated.

I've also included a solution I came up with while the competition was running. 670 Light. :) (which is probably now dark too hehe)
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ARFC_N_XXVIV_Dot_Results.zip
ARFC_N_XXVIV_Dot - Results
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Last edited by V4nKw15h on Wed Oct 24, 2007 2:03 am, edited 2 times in total.
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Postby FF » Tue Oct 23, 2007 4:05 pm

Dark medal can be given only if dark score is higher than light score.
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Postby NickyNick » Tue Oct 23, 2007 4:26 pm

Hersmunch's "light" solution uses hidden force, same as my recent "light" winning solution at A league: http://armadillo.metaclassofnil.com/for ... php?t=1542

For proof, you can compare Nahuelgq's and Hersmunch's structures. They have very similar (by shape and weight) constructions on the right half. Nahuelgq has to use several heavy metal plates to keep the whole structure balanced, but Hersmunch uses only one metal bar+rope and it seems quite enough.

Few words about my solution for A #CXX. If you replace rope on the right with metal bar (which is heavier), solution will fail.

This "hidden" force is usually produced by few metal bars and rope (as in my and Hersmunch's solutions).

Let's figure out what to do, it is very important!
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Postby Hersmunch » Tue Oct 23, 2007 5:26 pm

eh?
surely its not a bug. for one thing my solution is much lighter on the right and its built up from the anchor point as opposed to towards the right in the other one. Also by welding i managed to put more mass on the left (as far left as possible to increase the moment about the anchor point) that doesn't rest down on the anchor point as Nahuelgq did. Its just simple physics!

whats wrong with your solution? surely by adding more weight (the bar) it overbalances it...

im honestly not having a go at you, or anything like that. i just cant see what you mean by a bug. anyone else's thoughts?
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Postby NickyNick » Tue Oct 23, 2007 5:49 pm

Hersmunch wrote:surely its not a bug. for one thing my solution is much lighter on the right and its built up from the anchor point as opposed to towards the right in the other one. Also by welding i managed to put more mass on the left (as far left as possible to increase the moment about the anchor point) that doesn't rest down on the anchor point as Nahuelgq did. Its just simple physics!

Of course, it is simple physics! Please, be more attentive and have another look. We can see that length of left lever is equal in your and Nahuelgq's solutions. Also, length or right lever and weight on the right is approximately equal too. Despite this fact, Nahuelgq uses mass on the left which is about 5 times bigger than mass on the left used by you. And both structures are balanced! Isn't it strange?

Hersmunch wrote:whats wrong with your solution? surely by adding more weight (the bar) it overbalances it...

In the initial solution, right part seems to be heavier. When you replace rope with metal bar (which is heavier), the right part becomes... lighter! It is against physics laws too.
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ARFC_N_XXVIV_Dot.compare.lvl
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Postby V4nKw15h » Tue Oct 23, 2007 6:04 pm

Oh, :)

I posted the results just before leaving work and come home to find a debate raging. I didn't initially notice anything force related in hermunch's solution. I'll take another look now to see what NickyNick is talking about.

Scratch that, my girlfriend just walked in the door. Maybe later.


Okay I found some time. This is going to be difficult to explain unless you have a very good knowledge of physics but I can still see no problem with Hermunch's solution.

What you need to remember about force around a pivot is distance multiplied by mass = weight. An object of 4kg that is 2metre from the pivot will perfectly balance an object of 2kg that is 4metres on the other side of the pivot.

Nahuelgq's solution left a big hole in the right hand side and then placed a big chunk of weight out to the right. Further than Hermunch did. Hermunch was also very careful to thin out the weight on the right the further it extended away from the pivot. Hermunch also didn't leave a big hole and balanced all the central weight on both sides.

Hermunch's solution also rolls left at the start giving even more weight to the left of the structure. Nahuelgq shifts right giving extra weight to the right of his structure.

To my eye everything seems fine.

Not to mention my knowledge of physics gives no reason to believe that the welding in Hermunch's solution could possibly create extra rotational force. It is not a closed circuit so the energy can disipate properly. I see no bugs in the energy being abused.

I used exactly the same technique in the 670 solution I submitted. I didn't use welding to create force I used it to cheaply hang the metal bars as far from the pivot as a possibly could. Remember Distance x Mass = Weight.

I know physics, that's why I am a duck to water with this game.

Further opinions are obviously welcomed.
Last edited by V4nKw15h on Tue Oct 23, 2007 7:00 pm, edited 1 time in total.
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Postby Hersmunch » Tue Oct 23, 2007 6:48 pm

ok, i see what you say about size but he definitely used more material on the right. i attempted to mod it with my counterbalance...what do you think? it definitely is heavier cos i needed more material and had to move it further to the left.

you'll probably also be interested in seeing an earlier attempt i had. try replacing some of the supports with heavier metal sheets and see how much it effects the balance. compare this with replacing bits in Nahuelgq's solution. i know its not a completely fair test but it does show that my structure's right side has a smaller moment and wouldn't need as much to balance it.

What do you mean by the 'right part' in your solution? are you talking about replacing the rope on the top? i thought you meant the one dangling at first...i think that has something to do with rope actually being slightly slack when the sim starts. see the last two attachments for a similar effect (i think)
Attachments
ARFC_N_XXVIV_Dot.modded dot and arrow.lvl
(882 Bytes) Downloaded 180 times
ARFC_N_XXVIV_Dot.2.lvl
(760 Bytes) Downloaded 192 times
ARFC_N_XXVIII_Pony.b2.lvl
(1.38 KiB) Downloaded 186 times
ARFC_N_XXVIII_Pony.b.lvl
(1.39 KiB) Downloaded 184 times
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Postby NickyNick » Tue Oct 23, 2007 7:22 pm

V4nKw15h wrote:This is going to be difficult to explain unless you have a very good knowledge of physics...
...
What you need to remember about force around a pivot is distance multiplied by mass = weight.
...
Not to mention my knowledge of physics gives no reason to believe that the welding in Hermunch's solution could possibly create extra rotational force. It is not a closed circuit so the energy can disipate properly. I see no bugs in the energy being abused.
...
Remember Distance x Mass = Weight.

I know physics, that's why I am a duck to water with this game.

Well... I never like to talk as I will do now, but. So, you think that I don't know physics. Do you know that you are talking with silver medalist of All-Ukrainian physics olympiad?

For first, Distance x Mass doesn't equal Weight (newtons?!). Distance x Force = (in our case) Distance x Mass x g = Momentum.

To be balanced, algebraic summa of Momentums of construction elements should be equal zero. It means, that Momentum of left part should be equal Momentum of right part.

A bit later I'll calculate and post it for you, so you'll see that I'm right.
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Postby FF » Tue Oct 23, 2007 7:25 pm

Look this thread. It may help :)
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Postby NickyNick » Tue Oct 23, 2007 7:27 pm

FF wrote:Look this thread. It may help :)

That's exactly what I'm trying to explain :)
I'm making better pic now, especially for this level.
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Postby NickyNick » Tue Oct 23, 2007 7:56 pm

Let's assume that full metal bar weight 1kg. Some of them are a bit shorter though. As ropes and cloth don't weight very much, we'll not count them (anyway, they make right part heavier more, than left)

Look at picture. As you know (you are good in physics, you said), the place on the object, where Gravity is applied, is its center of mass - in our case, it is middle of each metal bar. On the picture, I marked x-coordinates (in pixels) of each center and anchor. Let's calculate Momentums of each metal bar:

Left part:
(320-73) * 1 = 247
(320-156) * 1 = 164
(320-278) * 0.7 = 29.4
(320-295) * 1 = 25
Summa = 465.4

Right part:
(352-320) * 1 = 32
(364-320) * 0.7 = 30.8
(409-320) * 0.7 = 62.3
(432-320) * 1 = 112
(489-320) * 0.7 = 118.3
(531-320) * 0.9 = 189.9
Summa = 545.3 (+ dillo, after landing)

So, the Momentum of left part is less, than Momentum of right part => there's hidden force in construction.
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explanation.png
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Postby NickyNick » Tue Oct 23, 2007 8:33 pm

So, as I understand, Dr.Dillo has won light, and Hersmunch has won dark. Congratulations!

p.s. Sorry for stealing your light medal, Hersmunch... We have some problems with determining lightness of solutions, so sometimes it is really hard to say, is solution light or dark. We all will be glad to see you winning in next competitions! :wink:
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Postby V4nKw15h » Wed Oct 24, 2007 2:19 am

Nice work Nicky Nick.

First apologies for my terminology in my rush to explain the physics. Good maths, bad terminology. My bad.

At first glance at your calculations I must admit I still had some doubts. You had calculated all the momentums based on the rigs initial state not it's final balanced state. So I went into the laborious chore of calculating the whole thing with the same methodology that you used.

There was some obvious force going on at the start to make the rig move left when you had proved it had momentum to go right. I wanted to check the final balanced state to see if there was still hidden force involved. For the sake of completism, not elitism.

I did a screen grab of the balanced state with the dillo and set about the laborious task of calculating it all. I also included the string and the cloth. It was really rather interesting, it was almost perfectly balanced, but you will be pleased to know...

It had a tiny bit extra momentum to the right and that was without the dillo being added into the equation. With the Dillo it should have rolled right quite easily.

So sorry Hermunch, NickyNick was right. Your solution is Dark, but because it beat the light you got the medal. :)

Good discussion all.

To NickyNick, no offense, I never accused you of not knowing physics. Read my initial comments again. They were not aggressive and not directed at you personally. They were only my initial observational opinions.

As before, further opinions are obviously welcomed. It's an interesting debate on the buggy physics when objects overlap.
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Postby Hersmunch » Wed Oct 24, 2007 9:30 am

well done on the workings and explanation guys, its nice. Sorry about making you do 'work' just for the lazy people like me.

just being cheeky but did anyone include the kinetic energy the bar on the left has just after it starts? :P I have a sneaky suspicion that when it comes down to it, all levels will be considered dark since the physics engine for the game is rather simple and things will never behave as in the real world.

I think the metal on bars on the right of my solution are actually being slowed down by the rope slightly. This can definitely be seen when comparing just metal bar to metal bar connected to rope when both are in free fall.

I'm happy either way, i mean a dark medal is probably harder to come by once im not a newbie...

Who hosts the next comp? I've made a level, its my first attempt and i have no idea if its any good.
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Postby V4nKw15h » Wed Oct 24, 2007 10:52 am

Hersmunch wrote:just being cheeky but did anyone include the kinetic energy the bar on the left has just after it starts? :P
Who hosts the next comp? I've made a level, its my first attempt and i have no idea if its any good.


Any kinetic energy involved at the start or created by the flying dillo is mute considering once it lands the whole rig remains perfectly balanced for a number of seconds until the level completes.

Everything settles down at this point and it was at this stable position that I took a screen capture of the whole thing, with the dillo caught in the catcher.

As I said, the structure itself was almost perfectly balanced (in its psuedo balanced state) if we ignore the dillo. But the dillo is still way to the right and should have easily rolled everything right.


As for the next competition, yet again we have a new member as the winner. DrDillo, like myself and Hersmunch when we won, is still awaiting forum activation. I just received an email from him and offered to host the next competition for him if he has a level ready. Waiting for a reply.
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