Energy stored problem

  1. Im really stuck with this question, hoping someone could give me a hand :cry:

    A bungee rope of unstretched length 50M is designed to allow a 70Kg man to come to rest 85m below the platform from which he jumps.

    Calculate the energy stored in the rope when the man has come to rest. Ignore the weight of the rope.
    (Gravitational field strength 9.8)


    Calculate the gravitational potential energy lost by the man when he comes to rest.


    Am i right to do
    70 x 9.8 = 686N
    Work Done = Force x Displacement
    =24.1Kj?

    Im not sure if im using the correct formula, and im totally stuck on the 2nd part :frown:
     
  2. jcsd
  3. pervect

    pervect 7,878
    Staff Emeritus
    Science Advisor

    Yes, that's right so far

    The displacement is wrong

    The second part is the key to the problem.

    Try reading

    http://id.mind.net/~zona/mstm/physics/mechanics/energy/gravitationalPotentialEnergy/gravitationalPotentialEnergy.html
     
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