Bungee Drop C

[TheLeftEye]

What do you guys think a good range for safety is at a competition? We use like 8 cm since temperature and stuff like that can affect everything. Also, we are using springs and we are getting really good results, but I have not seen a single team other than us use them. Any ideas why springs are bad?

[blindmewithscience]

I think that springs are generally not used beacuse
1) The chance of tangling on the way down is significantly higher for springs than other types of elastic cords
2) In section 3c, the elasticity test states "while being suspended vertically, the bottom meter of the cord must stretch to at least 1.25 meters when a single 500 g mass is attached to this section and return to within 5cm of its original length after the mass is removed." With many springs, they can stretch out because of their own weight, and won't return to their original length.

[FlyingMonkey85]

Does anyone remember what the combined drop distances were like for the medaling teams at nationals last year?

[chinesesushi]

Does anyone remember what the combined drop distances were like for the medaling teams at nationals last year?

I think first was like 4 centimeters, not sure though.

[DKluver]

So I built the measurement tool for bungee drop but I am not sure how to calibrate the device and what the final setup should look like. Any help would be great.

[blindmewithscience]

So I built the measurement tool for bungee drop but I am not sure how to calibrate the device and what the final setup should look like. Any help would be great.

Final setup for what? Drop apparatus, the bungee itself, or what? What do you need clarification on?

I was bored, so here's a road map for Bungee Drop.
1. Figure out what kind of cord you want to use. Partially elastic? Fully elastic? I talked about this with chalker earlier in the forum a bit. Decide which you want to use, as each has its own advantages and disadvatages.
2. Getting an equation for your cord. The equation for the partially elastic is available on the wiki, and one for a fully elastic cord, as i stated earlier, can be found by using initial and final energies and the modulus of elasticity.
3. Figuring out your "k" or "AE" value. This can be done by using a Vernier Force meter, or if you don't have that equipment, by attaching a mass to the bottom of your cord and finding out how much it stretched. Figure out the mass in Newtons, and bingo.
4. Drop Setup. As SOINC hasn't made a standard drop mechanism, this is basically up to you. Build something that can release your cord from the same position each trial. Or you could be inaccurate like my team, and hold the cord by had (which understandably produces some variation).
5. Test! For states, masses are between 50-300g in intervals of 10g (IIRC), while heights are between 2-5m. Try to get as many within that range as possible before your competition.

[zerasaw]

This is my method for bungee: I don't know how math-oriented you all are but this is the method our team used to beat a Solon team last year at Regionals.
You only need about 20 trials or so; the more the better. Take whatever cord you have and conduct separate trials on different lengths and masses. Then using Mathematica or similar software plot distance (z-axis) against mass and length (x- and y-axes) and you should be able to quadratic-model a surface equation for the drop. When you get the mass and height, you can plug the variables into the equation and it will spit out a length for you.
The reason Science Olympiad has these different intervals of mass for regionals is because they want to make it fair for those who do not have the calculus knowledge. But if you do, and ESPECIALLY if you're going to nationals (I know we're not), don't do a million trials. If you can, beat the system. LOL.

[chinesesushi]

This is my method for bungee: I don't know how math-oriented you all are but this is the method our team used to beat a Solon team last year at Regionals.
You only need about 20 trials or so; the more the better. Take whatever cord you have and conduct separate trials on different lengths and masses. Then using Mathematica or similar software plot distance (z-axis) against mass and length (x- and y-axes) and you should be able to quadratic-model a surface equation for the drop. When you get the mass and height, you can plug the variables into the equation and it will spit out a length for you.
The reason Science Olympiad has these different intervals of mass for regionals is because they want to make it fair for those who do not have the calculus knowledge. But if you do, and ESPECIALLY if you're going to nationals (I know we're not), don't do a million trials. If you can, beat the system. LOL.

The wiki has in-depth mathematical calculations provided some users on this site. A quadratic-model may or may not be accurate depending on the cord you are using. And also, that is hardly calculus knowledge

[zerasaw]

Yeah, I noticed those, but we have an all-elastic cord, and additionally it's pretty hard to surface fit a function, a quadratic model may or may not do the trick, it's a sort of warped planar thing. What I'm doing now is taking the normal vector to the surface at certain points around specs that we're looking at and solving for the tangent plane at that point...just tangent normalization of the surface around a certain point.
And it's not really calculus, just 3d geometry. In Ohio no one except Solon really teaches that in their high schools, not sure how early that's taught on the coasts.

[joiemoie]

This is my method for bungee: I don't know how math-oriented you all are but this is the method our team used to beat a Solon team last year at Regionals.
You only need about 20 trials or so; the more the better. Take whatever cord you have and conduct separate trials on different lengths and masses. Then using Mathematica or similar software plot distance (z-axis) against mass and length (x- and y-axes) and you should be able to quadratic-model a surface equation for the drop. When you get the mass and height, you can plug the variables into the equation and it will spit out a length for you.
The reason Science Olympiad has these different intervals of mass for regionals is because they want to make it fair for those who do not have the calculus knowledge. But if you do, and ESPECIALLY if you're going to nationals (I know we're not), don't do a million trials. If you can, beat the system. LOL.

The wiki has in-depth mathematical calculations provided some users on this site. A quadratic-model may or may not be accurate depending on the cord you are using. And also, that is hardly calculus knowledge

Also here's something interesting I found. The equation that I provided on the wiki, aka the real bungee equation for partial bungee cords, is very very linear. Before, I figured out the physics equations for this event, I tried to simply gather data and see if it followed a linear, or quadratic, etc. model. And I was shocked to see how precise the correlation was for a linear regression. Somewhere in the .99s.

In reality, its deceptively linear. If you actually graph the bungee equation I posted and keeping one of the variables constant, it follows an almost perfectly linear model. It's basically a line that wiggles back and forth as it rises in a negligible amount.