A problem with Gravitational and Elastic Potential Energy

[Poppy38]

I am calculating the energy transfer in two different formulas and they are giving different results. What could be the reason of this difference? I would be grateful if someone tell me what i am missing here.

http://s18.postimg.org/o4tknn77d/potential.jpg

 

[BvU]

Hello Poppy (!?) welcome to PF !

Does the weight hang still in the picture ?

 

[Poppy38]

The weight was at 1m high in pic.1
Then you connect it with the spring and release, it stays in equilibrium like pic.2

 

[BvU]

What happens if you release the weight ?
In particular: at the equilibrium line. Does it stop going down abruptly at this equilibrium line ?

 

[Poppy38]

So, is it going to have a 5J kinetic energy and swing for a time ?

 

[BvU]

You got it !
A point where you can do the energy check is when the weight reverses direction, i.e. at the lowest point: there the extension is two meters and the drop is 2 meters as well.

 

[Poppy38]

I've been thinking this for 3 days and at last i got it here. thanks so much :)

 

[BvU]

You're welcome !