Complex Physics...Work and Energy?

Question

In bungee-jumping, a daring student jumps from a balloon with a specially designed elastic cord attached to his ankles, as shown in Figure P5.69. The unstretched length of the cord is 28.0 m, the student weighs 705 N, and the balloon is 36.0 m above the surface of a river below.

Calculate the required force constant of the cord if the student is to stop safely 3.00 m above the river in N/m

I have no idea what to do. All I know is that I must convert gravitational energy (potential) to either elastic and kinetic energy somehow. Please help. A thorough explanation and reasoning would be greatly apprecitated. Please keep in mind that I am not able to use calculus methods such as integrals and derivitaves, but only transfer of energy.

Thank you. I promise the first person to thoroughly help me will get a best answer.

HAHA
i actually just solved it.
the answer ...about 1861.154 N/m

however, since i posted it as a ? if anyone can answer it with correct work, i'll still reward a best answer.

have fun.
and thank you all for helping me.

Answer 1

I will assume the balloon is stationary

I will also ignore air resistance

The energy of the jumper from the balloon to 3 m above the water is

m*g*h=705*33
23265 J

to stop the jumper the cord must absorb
that energy in
33-28=5m
the energy in the cord is related to
.5*k*x^2
k=2*23625/25
k=1890
j