# Homework Help: I need help to solve a problem with bunjee jumping

1. Oct 15, 2006

### trunks21

I need help to solve a problem with bunjee jumping!!!

I need to find the lengh and the K (spring constant) for a jump of 150ft. when they rebound they must avoid an obstacle that extends 15ft below the point at which they jump.

2. Oct 15, 2006

### OlderDan

What have you done to try to solve the problem? What additional information do you have about the bungee cord?

3. Oct 16, 2006

### trunks21

We start to solve with the conservatiion of energy

1/2ks^2 + 1/2mV^2 + mgh = 1/2ks^2 + 1/2mV^2 + mgh

but with that we only have when the mass not hit the ground, the hard part is how with the same information the mass when rebound not hit the 15ft obstacle bellow the start point???

the information of the cord is what we need to find using different long cord and different mass....

4. Oct 16, 2006

### OlderDan

The problem is that if energy is conserved you cannot avoid returning to the same height as you started. If the cord absorbs some energy (realistically it will) then you will return to a lower height. I don't know much about bungee cords. Do you have any specifications?