# Homework Help: Hooks Law

1. Nov 8, 2009

### joemama69

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

A massless hooksw law spring has a unstretched length of L, when a mass m is ploaced on it, and slowly lowered until the mass is at rest, the spring is queezed to a length of x. the mass is then dropped on the spring from a height of h, use energ methods

what is the length of the spring at maximum compression as a result of the mass dropping on it

2. Relevant equations

3. The attempt at a solution

mgh = -mgs + .5ks2

s = -mg + or -(((mg)2 - 4(.5k)(mgh))/k).5

if this is correct

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Last edited: Nov 8, 2009
2. Nov 8, 2009

### flatmaster

The question is worded aquardly, but I think you're on the right path with your firse equation. Now you need to write the spring constant k in terms of other parameters you have in your problem.

Also, you get two anilytical solutions. Can you think which sollution is correct? What does your non-physical solution correspond do?

3. Nov 8, 2009

### joemama69

what would be the benefit from solving for the spring constant

it asks for the length of the spring at compression s

4. Nov 8, 2009

### jgens

That way the spring constant is expressed in terms of other known parameters.

5. Nov 8, 2009

### joemama69

k = (2mgs - 2mgh)s2 = 2mg(s-h)/s2

i still dont understand how that helps, what would i use it for now