Bungee Drop

''Cow A Bungee redirects here. For Egg Drop events, see Naked Egg Drop and Rotor Egg Drop.''

Bungee Drop is a Division C event for the 2014 season. The object is to drop a mass attached to an elastic cord from a given height and to get the mass as close to the ground without letting it touch the ground. The heights for the two drops can be anywhere from two to five meters (Regionals/States) or ten meters (Nationals), either the same heights or two different heights (at Regional/States this is optional, but at National they will be different heights). After all devices are impounded impound, both the drop height and object mass will be announced. These weights will be anywhere from 50 to 300 grams.

The goal, as before, is to get your device to drop as close as possible to the floor below, without touching. The team with the lowest score for the sum of the two drops from the ground, wins. However, if one drop hits the surface, you will be ranked below (Tier 2) all teams that had no touches, and if you have two touches, you will be ranked below (Tier 3) all teams that had one or no touches.

General Advice
Read the event description carefully! The cord can be made from any materials, but the bottom meter must pass the 'elasticity' test. With the 2014 rules for elasticity tests, you don't have to make anything but the bottom meter of the device stretchy, if you so choose. While all sorts of materials can be used, from metal springs to Slinkys to elastic or rubber bands, some will be more reliable and will work better.

Practicing


The most important task to be done is calibration. Constructing a device may not be as difficult for Bungee Drop as it is for other events, but practice is key. Since elastic cords are not necessarily consistent in elasticity throughout, it is important to practice with multiple drop heights.

Creating a more reliable testing apparatus will allow you to have better data points to rely on at the competition. A typical bungee testing-device utilizes a soda bottle with mass contained in it and a clamp to hold the cord in place. It is recommended to also have a controlled method of releasing the bottle so that trials are systematic. For an example of a testing apparatus, see the image to the right.

Calibration this year promises to be more complicated than it has been in past years. If, say, you start calibration with a height of 3.00 meters, you can't only find one mark to make on our bungee for that height - you must make a mark for that height with 25 grams, for that height with 50 grams, etc. Getting the same degree of precision as was possible in past years will now, theoretically, take more the time (assuming you calibrate for, say 15 heights, and 15 masses). Of course, the real solution will to be to find a pattern; a formula. With a formula, you can simply input a mass and a height to know how long your cord should be.

Materials
The 2014 rules allow students to use any materials as long as they pass the 'elasticity' test. While this does give you a lot of freedom in deciding how you make your device, obviously some work better than others.

Competition Tips

 * At the competition, always be more cautious for new drop heights. Adjust the cord so that it is slightly shorter than you would expect.


 * If the two drop heights are the same, you can adjust the cord for the second drop depending on how close the first drop was.


 * If you use graphs to determine a formula, consider adding error bars to your graph so you can predict how careful you should be.


 * Some event supervisors will not disclose how close each of your drops was, so consider having your partner stand near the surface to observe how close each drop is.


 * The rules permit students to verify the mass of the bottle on their own. Since scales will vary in accuracy, consider using your scale to measure the mass so that it fits with your data.