Bungee Drop C

[wjnewhouse]

Does anybody know if we are allowed to bring in data about our bungee? Equations for displacement, tables of displacement etc? Are we also allowed to bring meter sticks with us?

I don't see why you wouldn't be able to bring any data with you. At every competition we've used a calculator during our bungee prep time with no problem from any event supervisors.

And rule 2a says you can bring measurement devices so bringing a meter stick should be fine. As long as you don't, as the rules says, "physically alter" your cord I'd say bring whatever tools/measuring devices you need.

[Mathc314]

I have a question about the physics behind this event...after testing our cord repeatedly and obtaining data for the length we must make the cord based on the height we're dropping from/the mass we're dropping from, my team has been trying to investigate the physics of the situation.
So here's my attempt at a physics solution: F=KX, so K=(Mg)/(height-initial cord length), but because the cord is a real spring, I'm calculating M by adding the mass we're dropping to one-third of the mass of the cord at that length. However, since our cord is made up of two parts, of which only one actually stretches, does anyone know of any equations or techniques we can use that will take into account the fact that the entire cord isn't stretching? Any help is appreciated; I think we've almost figured this out, but anything to make it more exact will be helpful (and I do know calculus, so if it does involve that, it's fine). Thanks!

[FawnOnyx]

I have a question about the physics behind this event...after testing our cord repeatedly and obtaining data for the length we must make the cord based on the height we're dropping from/the mass we're dropping from, my team has been trying to investigate the physics of the situation.
So here's my attempt at a physics solution: F=KX, so K=(Mg)/(height-initial cord length), but because the cord is a real spring, I'm calculating M by adding the mass we're dropping to one-third of the mass of the cord at that length. However, since our cord is made up of two parts, of which only one actually stretches, does anyone know of any equations or techniques we can use that will take into account the fact that the entire cord isn't stretching? Any help is appreciated; I think we've almost figured this out, but anything to make it more exact will be helpful (and I do know calculus, so if it does involve that, it's fine). Thanks!

Maybe a bit vague, but try thinking in terms of energies. For instance when the drop height and drop mass is provided, it may seem like two different variables you have to adjust for, but you could also think of it as giving you a gravitational potential energy.

[Mathc314]

Interesting idea...a couple more questions: at the point of maximum stretching, mgh=.5kx^2, so should I be using mass of the bottle at the bottom plus (1/3)*mass of the cord for the mass term in potential energy, or just the bottle portion? Also, is the best way to approach this to calculate k values for the cord based on each of our trials, or is there some other way this can be done?

[AH98]

What materials are you using to construct your bungee device? I purchased a bungee from home depot before I realized that it would not pass the "elasticity" test. It is pretty much now down to me ordering the materials online, and I have no way to test whether the strand/rope would meet the elasticity test requirements. What would you all recommend to use in the bungee cord?

Also, I found a few formulas that are bungee related on this website: http://www.real-world-physics-problems. ... mping.html

[chinesesushi]

have you tried using a spring or slinky? those usually pass the elasticity test easily, depending on the stiffness of the spring

[AH98]

I actually have not even put thought into non-rope materials, a slinky actually sounds really good to me. Marking it could be a problem though.

[chinesesushi]

you could mark each ring, and depending on your desired accuracy, make more marks (like 8 on every ring, or 16 on every ring). watch out for fatigue

[BuildistFromTheNorth]

At one of the competitions I went to earlier this year there was a team that used a slinky. They got knocked down to tier 2 because it didnt follow the rule that states the bungee must return to its original length. I would advise against using that.

[chinesesushi]

I don't see why it wouldn't return to its original length.