Spring Constant Question

[Jacko1394]

Hello everybody,
Can someone please go though and tell me how you would go about finding the spring constant?
I realise that some of the information they give you isn't needed for the answer 
Thanks.

[Phy124]

Ok, the way I used to always do these was by taking my reference point about the ground:







Now if the point at which the bungee jumper leaves is 19.6 m and the chord extends to 18m, therefore the bungee jumper is 1.6m off the ground at his lowest point.

Also, the original length of the chord is 10m and its length at maximum extension is 18m, therefore x = 8 m at the lowest point.







Alternatively, you can do it the easier way, where the gain in elastic potential energy will equal the loss of gravitational potential energy.

[Lasercookie]

We have Gravitational Potential Energy being converted to Elastic Potential Energy.

The cord is usually 10m long, and it extends to 18m, so x = 8m.



Solve for k.





and then significant figures and all that stuff.

edit: damn, I was too slow in posting

[Jacko1394]

WOW thanks so much guys, amazing response time, and both of you explained that really well.
I'm a tad unfamiliar with elastic potential energy and it's formula (1/2kx^2) :/
have to study up