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Tension and Force question

  • Thread starter Snikt
  • Start date
  • #1
Snikt
"An 80 kg person jumps off a bridge with a bungee cord of unstressed length 100 meters and a cross sectional area of 400 mm squared. Assume cord has zero weight, how far into the gorge does Bob plunge and what is the maximum force in the cord? The cord has a modulus of Elasticity E = 8 MPa."

The furthest I can get with this question is solving for mg = kx at the equilibrium point, and the distance from that point to the unstretched 100 meters is around 124 meters. How do I carry forward is beyond me. Can someone please explain to me how I can solve for the distance from the equilibrium point to the bottom of the plunge?

Thanks for your time.

Snikt
 

Answers and Replies

  • #2
Chi Meson
Science Advisor
Homework Helper
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10
I don't know if you are at this point, but if you solve using conservation of energy, it would be simpler:

At the farthest stretch of the cord, a certain amount of gravitational potential energy is transformed into elastic potential energy. call "y" the maximum stretch of the cord and "y + 100" the height the jumper has fallen.
 

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