A long bungee cord obeys Hooke’s law up to an extension of and has a spring constant of

PHYSICS · Subjective · CBSE · Physics · Work, Energy and Power · Work, Energy and Power

Problem

2.5\,\text{m}

long bungee cord obeys Hooke’s law up to an extension of

1.5\,\text{m}

and has a spring constant of

150\,\text{N}\,\text{m}^{-1}

. A physics student of mass

55\,\text{kg}

decides to jump off a low bridge using this cord attached to his waist. The bridge deck is

8.0\,\text{m}

above the surface of a calm lake. (a) Determine the gravitational potential energy lost by the student just before the cord starts to stretch. (b) The student comes momentarily to rest after the cord has stretched by its maximum safe extension of

1.5\,\text{m}

. Calculate the elastic potential energy stored in the cord at that instant. (c) Using energy conservation, find whether the student will touch the water surface or not. Show all working clearly. (d) State two assumptions made in your calculation that might differ from real-life conditions, and explain how each could affect the actual outcome.

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