physics

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A bungee jumper jumps from a bridge with a 3 m long bungee cord. Once the cord starts to stretch, it acts like an ideal spring with coefficient of elasticity k=100 N/m. What should be the minimum height of the bridge in m so that this jump is safe for the jumper?

Details and assumptions
The jumper has a mass of 80 kg.
The acceleration of gravity is −9.8 m/s^2.
There are at least two ways to solve this problem.
Treat the jumper as a point mass at the end of the cord.

  • physics -

    potential energy decrease in fall = potential energy put into spring

    m g h = (1/2) k h^2

    h = 2 m g /k

  • physics -

    i think we will get from your way damon h be about 15.68 which is wrong..

  • physics -

    no no your correct but correct answer will bet putting h-3 in place of h..

  • physics -

    Oh, yes, sorry

  • physics -

    so whats the correct answer?

  • physics -

    The correct answer is 21.276

    Consider the law of conservation of energy in solving this problem.

    i.e. gravitational potential energy = elastic potential energy.
    So, m g (h-3) = 1/2 k x^2.

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