A bungee cord has an unstretched length of 20.0 m. When it is stretched an addit

Question

A bungee cord has an unstretched length of 20.0 m. When it is stretched an additional length x, it exerts a restoring force of magnitude kx. Your friend (mass 60.0 kg) stands on a bridge 50.0 m above the surface of a river. One end of the cord is tied securely to her ankle and the other end to the bridge. You promise her that when she steps off of the bridge that she will fall a maximum distance of only 45.0 m before the cord stops her. You have several types of bungee cords to select from (all with unstretched length 20.0 m), and you test them by tying one end to a tree and pulling on the other end with a force of 350 N. When you do this, what distance will the bungee cord that you should select have stretched? Please begin with a 1-2 sentence discussion of your strategy.

Explanation / Answer

according to hooke's law

F = k*x

here x = 45-20 = 25 m

then F = 60*9.81 = 588.6

cord constant k = F/x = 588.6/25 = 23.544 N/m

then now apply again F = k*x

350 = 23.544*x

x =350/23.544 = 14.86 m

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