Length of bungee cord?

  • Thread starter raindropecho
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  • #1
raindropecho

Main Question or Discussion Point

Hi I'm having trouble with a certain question. Could someone please guide me to the right answer? Thanks
"Consider a 70 kg person leaping off a 226m building. He plans to use a rope with force constant 4900 N/m. What length of rope does he need to stop his plunge 10m above the sidewalk? What max force will the rope exert on him?"
Any help is greatly appreciated
 

Answers and Replies

  • #2
russ_watters
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Construct an equation with those 3 peices of information using length as your variable and solve it. Each side will be an energy equation. There are two important things to consider: the gravitational potential energy at the beginning (when on the roof) is exactly equal to the potential energy in the spring (bungee cord) when the person is 10m off the sidewalk (make that the zero point to make the calculations easier and make the building 216m). And second, remember that for the first part of the plunge, the bungee cord isn't stretching.
 
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