Spring constant and bungee jumping.

[anotherperson]

Homework Statement

68kg bungee jumper standing on a 46m platform above the ground. The bungee cord has no effect for 9m(ie natural cord length is 9m)

when the bungee jumper is more than 9m away the spring constant is k=66N/m

a)what is his speed after falling 9m from the platform?
b)what is his speed after falling 31m from the platform?
c) sketch the position-time graph.

Homework Equations

The Attempt at a Solution

a) vf^2=0^2 + (2x9.8x9)
=13.3 m/s

b) for b I'm not sure how to factor in the spring constant. and i don't know if i should factor it in from the start or after 9m, I am assuming after 9m. i think it relates to Usp=.5kx^2

c) for the graph it would just be a parabola right? no need to draw one for me.

 

[da_nang]

b) for b I'm not sure how to factor in the spring constant. and i don't know if i should factor it in from the start or after 9m, I am assuming after 9m. i think it relates to Usp=.5kx^2

It does relate to the elastic energy. Energy is conserved, so that's a good way to start.

c) for the graph it would just be a parabola right? no need to draw one for me.

Only for constant acceleration. Is it in this situation?