Bungee Drop C

[chalker]

Does anyone know where to get elastic bang or metal springs that will meet the required k value, i cant seem to find a meter or more elastic material of any kind that has an appropriate k value for the event. Last I could not find anything that was a meter long so i had jerryrig 5 rubber bands tied together. Our testing was incredibley inconsistent, we need a new material and i cant seem to find anyhting on line or in the area that will work. Does anyone have any ideas.

One item you can try is Therabands (used in most Physical Therapy clinics), which come in different resistances. You could try asking for some for free from a local PT clinic or maybe even the athletic trainer at your school. If you want to buy them, they are available at a lot of places, such as Amazon:
http://smile.amazon.com/Thera-Band-Extr ... therabands

P.S. - if you shop Amazon, please consider using Amazon Smile (smile.amazon.com). The prices are the same, but a portion of your purchase goes to a charity of your choice. And Science Olympiad is one of the charities you can choose!

[Nate711]

Hi. I'm wondering if for the elasticity test the proctors hold the cord from the 1m mark and then apply the mass or if they hold the cord from a different place. The rules say the bottom meter is suspended vertically, but it doesn't explicitly say where it will be held from. (I submitted a FAQ, but no response yet). Thanks!

[chinesesushi]

Hi. I'm wondering if for the elasticity test the proctors hold the cord from the 1m mark and then apply the mass or if they hold the cord from a different place. The rules say the bottom meter is suspended vertically, but it doesn't explicitly say where it will be held from. (I submitted a FAQ, but no response yet). Thanks!

What do you mean hold the cord from a different place. The bottom meter (which includes the key ring) should stretch to 1.25 meter or more.

[Nate711]

As in, at which point do they attach the cord to the wall (or stairwell etc)?

[blindmewithscience]

As in, at which point do they attach the cord to the wall (or stairwell etc)?

I assume that they'll take the point that's one meter away from the bottom, attach it to something or hold it, and then attach the 500g mass. Could you explain how the judges could measure how far the bottom meter stretched if they held somewhere other than the bottom meter?

[chinesesushi]

As in, at which point do they attach the cord to the wall (or stairwell etc)?

Measuring from the bottom of the key ring which is at the bottom of the cord, 1 meter up is will they will attach it to wherever they're attaching it too.

[blindmewithscience]

Exactly how much theoretical calculantions are you guys doing for this competition? Our team has derived an equation for the length of the cord with a given height and mass, and we're using that to estimate our drops (which so far is somewhat accurate).
Also, how many tests with your cord have you done so far/plan to do before the competition?

[sciolymom]

When measuring the drop height, is the height measured from the top edge of where the cord is attached on the drop mechanism?

Hope I am asking this in a way that makes sense.... if you look at the pictures in the gallery for example. The cord is attached with a clamp and then goes over the edge of the 2x4. Is the top of the 2x4 where the drop height is measured? The release mechanism height has no affect on this, is that correct?

Thank you!

[bernard]

An FAQ was posted for this question on the official Science Olympiad website.

What is the definition of "drop height?"is it the bottom of the plastic bottle? The top? the top including all attached pieces by the event supervisors?The height of the anchoring system's top of ledge? (section: 3 / paragraph: b / line: 1)
The drop height is measured from the bottom of the bottle.

[sciolymom]

??? Ok....so our device ends at the key ring. The supervisor can use whatever they choose to attach the bottle to the key ring. They could have, for example, an o ring plus a carbiner, or maybe just an o-ring, or even some duct tape plus a carbiner. All of that could change the height of "the bottle". Also, the dropping mechanism could be totally different from what we are testing with. For example...our cord attaches to the ledge. Our release mechanism is a little bit above that, which would determine where the "bottom of the bottle" ends up. If the drop mechanism is different at the competition, that could change the distance between the cord attachment and the bottom of the bottle.

Am I not understanding this right, or does that not make it impossible to test accurately?