# Conservation of energy – spring

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

Hello, I’m having a problem with this. So we drop the weight on this spring, and the question is: how much does the spring compress? The mass is 5kg, the height 0,4m, and the spring elasticity factor k=1700N/m.

**2. Relevant equations**

**3. The attempt at a solution**

I’ve tried to equalize the potential energies of when we drop the weight, and when it’s all the way down. It looks like this: m(h+ΔL)=(1/2)*k*(ΔL)^2. I get a quadratic equation, and solve it. I get two answers one with +, and one -. I’ve tried to enter the positive one, and it’s not correct. Should I enter the negative one, or is my whole attempt faulty?

http://ift.tt/1fIg9Ty

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