(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A bungee jumper needs to calculate how much bungee cord to attach to herself so that it will bring her to rest 3m above ground. The spring constant of the bungee cord is 22 N/m, and she has a mass of 55kg. Neglect the bungee cord's mass.

a.How long a bungee cord is required?

b.If she uses the length calculated inabut the spring stiffness is 10 percent less than it was advertised to be, how fast will she hit the ground?

The bungee jumper is standing 70m above the ground.

2. Relevant equations

PE(g)=mgh

PE(sp)=1/2kx^2

KE=1/2mv^2

3. The attempt at a solution

For partaI used this equation:

PE(g)=PE(sp)+PE(g)

55(9.81)(70)=1/2(22)*x^2+(55)(9.81)(3)

x=57.3 m

For partbI used this equation:

PE(g)=PE(sp)+KE

55(9.81)(70)=1/2(19.8)(57.3)^2+1/2(55)v^2

v=13.835 m/s

The correct answer is 7.95 m/s for partb.

So I am not sure if my partais wrong or if I am not setting up my equation correctly.

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# Homework Help: Bungee Jump - Potential and Kinetic Energy

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