How to calculate the spring constant in an elevator fall scenario?

[gb14]

Homework Statement

An engineer creates a spring so that when an elevator falls from a height h, the spring constant k, only allows the elevator to reach an acceleration of 5g's. Let M be the total mass of the elevator and passengers. Solve for K

Homework Equations

F=-kx
1/2mv^2 + mgh + 1/2kh^2 = 1/2mv^2 + mgh + 1/2kh^2
v=\sqrt(2gh)

The Attempt at a Solution

I know you have to break it up into two separate equations to find the velocity of the elevator up to where it hits the spring and then to how much the spring compresses but I feel like I'm missing information.

 

[PhanthomJay]

You forgot to post the question as to what you are trying to solve.

 

[gb14]

You forgot to post the question as to what you are trying to solve.

My bad, I edited it. I have to solve for the spring constant, k.

 

[PhanthomJay]

Ok, one way would be as you say, to break the problem into parts: first find the velocity of the elevator just before it hits the spring (the spring does not enter into the equation in this step); then now, as part 2, when it compresses the spring until it comes to a momentary stop, you can calculate the full distance the spring compresses, using the kinematic equations, then you'd need additional equations (like Newton's laws) to solve for k. Please show your attempt at a solution, and someone will help guide you through your method and errors, if any. You must attempt this before we can be of further assistance.