An elastic bungee cord can be modeled as an ideal spring with spring constant

PHYSICS · Multi-part · CBSE · Physics · Work, Energy and Power · Work, Energy and Power

Problem

An elastic bungee cord can be modeled as an ideal spring with spring constant k=150 N m−1k=150\,\text{N}\,\text{m}^{-1}. The unstretched length of the cord is defined as Δx=0\Delta x=0. A 70 kg70\,\text{kg} jumper steps off a platform and, at the lowest point of the jump, the cord is stretched downward by 1.80 m1.80\,\text{m}. Air resistance is negligible. (a) Calculate the elastic potential energy stored in the cord when it is stretched by 1.80 m1.80\,\text{m}. (b) On the axes below, sketch a graph of the cord’s elastic potential energy UU (vertical axis) versus stretch Δx\Delta x (horizontal axis) for 0≤Δx≤2.0 m0 \le \Delta x \le 2.0\,\text{m}. Label the value of UU at Δx=1.80 m\Delta x=1.80\,\text{m} calculated in part (a). (Provide a clear verbal description of your sketch in your response.) (c) Using your graph, determine the additional amount of elastic potential energy stored as the stretch increases from 1.40 m1.40\,\text{m} to 1.80 m1.80\,\text{m}. Show how the graphical representation supports your numerical result.

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