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Homework Help: I need help with this homework please help

  1. Dec 13, 2007 #1
    i need help with this !!! please help

    here's the problem
    Bungee core originally is 15m (meter) long. When a 500N (newton) weight is hung from it , the new length is 17m( it stretches 2 meters)
    a) what is the spring constant of the bungees core
    b) how long a bungee should be if a 60kg woman use it to jump off a 30m (meter) tall platform.
    c) what tretch does equilibrium occur?
    d) what maximum speed is reached?

    please please help me it's urgent
    u only need to do c and d because i already figured out a and b
    thanks a lot thanks thanks thanks:cry::confused::confused::cry::uhh::uhh:
    Last edited: Dec 13, 2007
  2. jcsd
  3. Dec 13, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    Welcome to the forums. We have a policy here that we do not do homework for students, and we do not help until the student shows his/her work. So, what have you done thus far? Perhaps you could post the work you have done on the first two parts, and how you think you should attack the next part.

    Oh, and in future, please note we have specialised homework forums in which you should post your problem.
  4. Dec 13, 2007 #3
    sorry this is my first post to this forum
    it's my mistake but can anyone help me with this problem?\thank you
  5. Dec 13, 2007 #4
    ok this is the first two part
    F=-kx ( F is force, k is the spring constant, and x is the distance the bungee stretche)
    k=250n/m( that is the spring constant)

    Potential energy / Kinetic energy / Energy of the bungee /Total energy
    60x10x30 0 0 18000jouls

    0 0 1/2x250x X Square 18000jouls
    X=12 meter (how long the bungee will stretch) 30-12=18 meter( how long the bungee core need to be)
    hint : little x stands for multiplication sign
    someone please help me with c and d​
    thank you[/CENTER][/LEFT]
    Last edited: Dec 13, 2007
  6. Dec 13, 2007 #5


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    Staff Emeritus
    Science Advisor

    Presumably c and d are based on a 60 kg woman dropping from a 30 m platform.

    c. Max stretch at equilibrium occurs with the 60 kg woman hanging

    d. What happens when the bungee starts stretching?
    Last edited: Dec 13, 2007
  7. Dec 13, 2007 #6
    For c), is it asking what's the extension of the rope when the woman is hanging?

    For d), this one is quite easy... At what point of the descent will the woman have the maximum speed?
  8. Dec 13, 2007 #7
    i think about D but i cant get the answer for it
    can you please show me how to do it ? cause im not really goood at physic
  9. Dec 13, 2007 #8
    ok this is the answer that i got for D
    maximum speed of the woman is 24.24m/s^2
    is this right please help me
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