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Conservation of Energy

  1. Nov 4, 2007 #1
    A bored college student decides to try bungee jumping. He attaches an elastic bungee cord to his ankles and happily jumps off a tall bridge across a river. He ends up barely touching the water before the cord jerks him back up

    The length of the relaxed cord is y_e; the distance from the bridge to the river surface is y_0 (where y_o>y_e), and the spring constant of the elastic cord is k.

    Which assumptions are reasonable to make in this problem?

    a.The student can be treated as a particle moving with constant speed.
    b.The student can be treated as a particle moving with constant acceleration.
    c.The student cannot be treated as a particle.
    d.The air resistance is substantial.
    e.The air resistance is negligible.
    f.The amount of heat generated in the bungee cord is substantial.
    g.The amount of heat generated in the bungee cord is negligible.
    h.The bungee cord applies a constant (or zero) force on the student.
    i.e bungee cord can be modeled as a spring that obeys Hooke's law.

    I tried BEGI, CEGI, BEGH, AEGI. And they are all wrong. I need help.
     
  2. jcsd
  3. Nov 4, 2007 #2

    learningphysics

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    EGI look alright to me.

    A doesn't work... B doesn't work either because the force exerted by the bungee on the person changes with time... ie net force on the student changes, so acceleration changes.
     
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