# Compression of a spring.

1. Nov 2, 2009

### gb14

1. The problem statement, all variables and given/known data 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

2. Relevant equations

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

3. The attempt at a solution

I know you have to break it up into two seperate 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.

Last edited: Nov 2, 2009
2. Nov 2, 2009

### PhanthomJay

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

3. Nov 2, 2009

### gb14

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

4. Nov 2, 2009

### 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.

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