Descending elevator stops determine displacement of mass on spring

[jm1379]

Hey guys i am very stuck any help appreciated. I do not know where to start.

The equations used need to be derived from first principles and accurate free body diagrams drawn.


An elevator moves downwards at a constant velocity v0. While descending, at a particular height (assuming t=0), the velocity of the elevator decreases until zero in a time t0. Assuming the velocity is a parabolic function of v0 [1-(t/t0)^2]. Determine the displacement x of the mass m for t less than or equal to t0. Assuming z= x - u

Here is a link to the image
http://img5.imageshack.us/img5/6618/springi.png

 

[voko]

First select some reference frame.

 

[jm1379]

So Assume downwards is + to try and eliminate negative numbers?

 

[voko]

"downwards +" is a not a reference frame.