Bungee Drop C

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chinesesushi
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Re: Bungee Drop C

Post by chinesesushi »

chalker wrote:
chinesesushi wrote:
Flavorflav wrote:We actually saw one at an invitational that was gently lowered by a motor with a remote. It won, which would really have p!ssed me off if it were not an invitational.
LOL well that's not allowed XD

It's clearly a spirit of the problem violation, however it's not explicitly prohibited in the rules, so perhaps a FAQ is in order.
I believe there was a FAQ last year that explicitly addressed using a motor, but there doesn't appear to be one this year. XD
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Re: Bungee Drop C

Post by joiemoie »

blindmewithscience wrote:Well, the value of k changes depending on the length of your cord, even with the same material. You'd need a different formula to figure out a constant that also factors in a changing length (hint hint, one exists).
If you are using rubber bands:
1. Make sure that your cord can meet the test for elasticity. The bottom 1 meter should stretch to 1.25m with a 500g mass attached to the bottom.
2. The main problem I foresee with rubber bands is consistency in the elasticity of the rubber bands. Due to the nature of rubber bands, there will be some variation in their elasticity. This will lead to a cord that's more elastic in some parts and less elastic in other parts. This could lead to errors in you calculations.

One more thing: testing is huge in this event. Knowing beforehand how well your equation matches up with reality helps you a ton in the competition.
The problem with the constantly varying "k" value is not an issue at the nationals level, where the drop heights are between 5 and 10 meters. At that height, you will have measured far past the elastic portion of your rope and into the non-elastic portion, at which point the "k" value of the elastic portion creates no variation. Furthermore, the chance that you will have to go into the elastic portion of the rope during a states or regionals competition is very, very slim, since it would require a very short drop height and heavy mass. Based on my calculations, the chance of that happening at a regionals tournament for most of the bungees where the length of the elastic portion is around 1 meter is roughly 3.7%. And even under those circumstances, if you do happen to have to go into the elastic portion, it would only make it harder to tier and simply add a bit of height to your drop.
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Re: Bungee Drop C

Post by joiemoie »

Note: i uploaded my bungee equations to the wiki, so feel free to use them.

One issue that many bungee drop competitors face is the issue of varying elasticity the more you test it. More specifically, the more you test it, the less elastic your bungee will become. One great way to account for this is to use measuring tape for the actual non-elastic portion itself. Even if the "k" value for your bungee changes over time, the bungee cord will become longer also to compensate for this. This will cause the actual measuring tape itself to shift along with the increasing length of the elastic portion of the bungee over time, simulating a constant k value.

If you don't understand what that means, the implications of this are that if you are using math equations for your bungee, you should use measuring tape for the non-elastic portion of your rope rather than using a non-elastic rope and measuring it everytime from the ring to the top.
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Re: Bungee Drop C

Post by chalker »

joiemoie wrote:Note: i uploaded my bungee equations to the wiki, so feel free to use them.

One issue that many bungee drop competitors face is the issue of varying elasticity the more you test it. More specifically, the more you test it, the less elastic your bungee will become. One great way to account for this is to use measuring tape for the actual non-elastic portion itself. Even if the "k" value for your bungee changes over time, the bungee cord will become longer also to compensate for this. This will cause the actual measuring tape itself to shift along with the increasing length of the elastic portion of the bungee over time, simulating a constant k value.

If you don't understand what that means, the implications of this are that if you are using math equations for your bungee, you should use measuring tape for the non-elastic portion of your rope rather than using a non-elastic rope and measuring it everytime from the ring to the top.
Note you are assuming there is a non-elastic portion of the cord. I've seen many devices that are completely elastic.

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Re: Bungee Drop C

Post by blindmewithscience »

chalker wrote:Note you are assuming there is a non-elastic portion of the cord. I've seen many devices that are completely elastic.
In addition, there are many advantages to having an all-elastic cord.
1-It wears out slower than cords with a non-elastic portion, as it slows it down over a longer period of time and a longer distance.
2-The mass slowing down over a longer period of time can help you score higher. How? Suppose that a camera were videoing 2 cords that both got to 5cm above the ground, with one fully elastic and the other only partially elastic. The partially elastic cord is accelerating much faster at the bottom than the fully elastic one. If you look at the video of the partially elastic cord, there will be a lot of change from frame to frame, and so the very bottom probably won't be caught on camera. However, the video of the fully elastic one will accelerate slower at the bottom, and so you can more easily see the bottom on camera.
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Re: Bungee Drop C

Post by joiemoie »

blindmewithscience wrote:
chalker wrote:Note you are assuming there is a non-elastic portion of the cord. I've seen many devices that are completely elastic.
In addition, there are many advantages to having an all-elastic cord.
1-It wears out slower than cords with a non-elastic portion, as it slows it down over a longer period of time and a longer distance.
2-The mass slowing down over a longer period of time can help you score higher. How? Suppose that a camera were videoing 2 cords that both got to 5cm above the ground, with one fully elastic and the other only partially elastic. The partially elastic cord is accelerating much faster at the bottom than the fully elastic one. If you look at the video of the partially elastic cord, there will be a lot of change from frame to frame, and so the very bottom probably won't be caught on camera. However, the video of the fully elastic one will accelerate slower at the bottom, and so you can more easily see the bottom on camera.
I'm not exactly sure about your first advantage, however the second reason is completely valid. However, I think that issue is mostly a concern with how accurate event directors are willing to go, and i think that at nationals, accuracy in measuring should not be a concern (they might also use those sensors that can also accurate tell distance, at which framerate doesn't even come into play).

The main advantage with a partially elastic bungee is that the equations are
1) Much easier to work with since you're working with a constant "k" value.
2) An entire length bungee would have to take into account k values at various lengths along the cord, something not easy to do. (I checked to see if it followed a y=kx or yx=k type relationship and neither worked) Equations modeling k values for elastics stretching at different points are very difficult to find and specific, and creating an experimental equation for k values at different locations give lots of room for error.
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Re: Bungee Drop C

Post by chinesesushi »

IMO, at nationals last year, Bungee Drop was run worse than at the MIT invitational this year. It was also run worse than an invitational that I attended at my school. The event supervisor was not to particular in their measurements, to say the least. It would be fantastic if the guy who ran it at MIT invitational also ran it at nationals this year, because the system they had was quite good and worked well. He also happened to volunteer at nationals last year XD.
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Re: Bungee Drop C

Post by joiemoie »

chinesesushi wrote:IMO, at nationals last year, Bungee Drop was run worse than at the MIT invitational this year. It was also run worse than an invitational that I attended at my school. The event supervisor was not to particular in their measurements, to say the least. It would be fantastic if the guy who ran it at MIT invitational also ran it at nationals this year, because the system they had was quite good and worked well. He also happened to volunteer at nationals last year XD.
Really? I was at the MIT invitationals this year, and i must say, that was probably worse administration than i had seen than in even regionals. I was part of block 1, where all the issues occurred. First the mass was recorded to be 306 grams (already going past specifications) then changed to 297 grams (suggesting inaccuracy in equipment). Next, they used a laser to measure drop height, ended up measuring incorrectly (4.31m but in reality 3.81m) and had to request teams that tiered to come back another block and try again. They had to redo all the measurements on the spot using rather imprecise ruler measurements. Next, they used carabiners (which they even admitted later should have probably used clamps since many teams unfairly had their bungees slip off due to poor attachment to carabiner. also they are just overall worse than clamps). Finally, even the top placing MIT scores were worse than usual, even with teams from top national schools such as troy. 50 cm very poor, especially when the yale top placing scores were about 2cm. The fact that even normally solid teams did this poorly suggested a problem with the overall event. Also, they put one team from our school in tier 6 by accident and gave it 39th place. It passed the elasticity test. It did not hit the ground on either drop. It was impounded. Had our team not experienced the false tier, it wouldve given us enough points to surpass troy high school for 3rd :'( oh well

Also all of these problems were sent to the MIT Science Olympiad director, and as quoted "Regardless, please rest assured that we treat these possible issues gravely seriously, and we have thoroughly addressed the items you mention with our Bungee Drop event supervisor, who will not be invited to supervise events at any Science Olympiad at MIT tournament in the future. It is particularly embarrassing to me that these problems arose with Bungee Drop, given the care with which we vetted and selected our event supervisors, and especially because our Bungee Drop event supervisor has been intimately involved with planning and running the event at the national tournament."
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Re: Bungee Drop C

Post by chinesesushi »

joiemoie wrote:
chinesesushi wrote:IMO, at nationals last year, Bungee Drop was run worse than at the MIT invitational this year. It was also run worse than an invitational that I attended at my school. The event supervisor was not to particular in their measurements, to say the least. It would be fantastic if the guy who ran it at MIT invitational also ran it at nationals this year, because the system they had was quite good and worked well. He also happened to volunteer at nationals last year XD.
Really? I was at the MIT invitationals this year, and i must say, that was probably worse administration than i had seen than in even regionals. I was part of block 1, where all the issues occurred. First the mass was recorded to be 306 grams (already going past specifications) then changed to 297 grams (suggesting inaccuracy in equipment). Next, they used a laser to measure drop height, ended up measuring incorrectly (4.31m but in reality 3.81m) and had to request teams that tiered to come back another block and try again. They had to redo all the measurements on the spot using rather imprecise ruler measurements. Next, they used carabiners (which they even admitted later should have probably used clamps since many teams unfairly had their bungees slip off due to poor attachment to carabiner. also they are just overall worse than clamps). Finally, even the top placing MIT scores were worse than usual, even with teams from top national schools such as troy. 50 cm very poor, especially when the yale top placing scores were about 2cm. The fact that even normally solid teams did this poorly suggested a problem with the overall event. Also, they put one team from our school in tier 6 by accident and gave it 39th place. It passed the elasticity test. It did not hit the ground on either drop. It was impounded. Had our team not experienced the false tier, it wouldve given us enough points to surpass troy high school for 3rd :'( oh well

Also all of these problems were sent to the MIT Science Olympiad director, and as quoted "Regardless, please rest assured that we treat these possible issues gravely seriously, and we have thoroughly addressed the items you mention with our Bungee Drop event supervisor, who will not be invited to supervise events at any Science Olympiad at MIT tournament in the future. It is particularly embarrassing to me that these problems arose with Bungee Drop, given the care with which we vetted and selected our event supervisors, and especially because our Bungee Drop event supervisor has been intimately involved with planning and running the event at the national tournament."
Ehh I guess they had resolved all their issues by the time our team went. Troy screwed up in Bungee lol, 50 cm is very poor XD. Yeah idk I guess when I saw it run they looked pretty accurate and well-run, I'm sorry you had those issues :( how was your actual score without the tiering and such?
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Re: Bungee Drop C

Post by joiemoie »

chinesesushi wrote:
joiemoie wrote:
chinesesushi wrote:IMO, at nationals last year, Bungee Drop was run worse than at the MIT invitational this year. It was also run worse than an invitational that I attended at my school. The event supervisor was not to particular in their measurements, to say the least. It would be fantastic if the guy who ran it at MIT invitational also ran it at nationals this year, because the system they had was quite good and worked well. He also happened to volunteer at nationals last year XD.
Really? I was at the MIT invitationals this year, and i must say, that was probably worse administration than i had seen than in even regionals. I was part of block 1, where all the issues occurred. First the mass was recorded to be 306 grams (already going past specifications) then changed to 297 grams (suggesting inaccuracy in equipment). Next, they used a laser to measure drop height, ended up measuring incorrectly (4.31m but in reality 3.81m) and had to request teams that tiered to come back another block and try again. They had to redo all the measurements on the spot using rather imprecise ruler measurements. Next, they used carabiners (which they even admitted later should have probably used clamps since many teams unfairly had their bungees slip off due to poor attachment to carabiner. also they are just overall worse than clamps). Finally, even the top placing MIT scores were worse than usual, even with teams from top national schools such as troy. 50 cm very poor, especially when the yale top placing scores were about 2cm. The fact that even normally solid teams did this poorly suggested a problem with the overall event. Also, they put one team from our school in tier 6 by accident and gave it 39th place. It passed the elasticity test. It did not hit the ground on either drop. It was impounded. Had our team not experienced the false tier, it wouldve given us enough points to surpass troy high school for 3rd :'( oh well

Also all of these problems were sent to the MIT Science Olympiad director, and as quoted "Regardless, please rest assured that we treat these possible issues gravely seriously, and we have thoroughly addressed the items you mention with our Bungee Drop event supervisor, who will not be invited to supervise events at any Science Olympiad at MIT tournament in the future. It is particularly embarrassing to me that these problems arose with Bungee Drop, given the care with which we vetted and selected our event supervisors, and especially because our Bungee Drop event supervisor has been intimately involved with planning and running the event at the national tournament."
Ehh I guess they had resolved all their issues by the time our team went. Troy screwed up in Bungee lol, 50 cm is very poor XD. Yeah idk I guess when I saw it run they looked pretty accurate and well-run, I'm sorry you had those issues :( how was your actual score without the tiering and such?
With the inaccuracies, about 50ish cm. However, when we tested at the previous tournament, yale, and also regionals, we got 6cm for yale and 2cm for regionals. At least you had a good experience :)
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