Calculating Spring Constant for an 8kg Stone Resting on a Compressed Spring

[suspenc3]

An 8kg stone rests on a spring. the spring is compressed 10cm by the stone.

What is the spriong constant?

im not really sure how to start...Ws = -0.5kx^2

im guessing that there must be a relationship between Wg and Ws obviously
-Wg = Ws... but I am not sure how to solve for Ws

Can anyone help?

 

[cscott]

F = mg = -kx

 

[suspenc3]

b)the stone is pushed down an extra 30 cm. What is the elastic potential energy of the compressed spring just before the release?

U = 0.5kd^2 d=distance compressed

...U = 6.27 x 10^-3 J

ok...the next part asks for...

what is the change in the gravitational potential energy of the stone-earth system when the stone moves from the release point to its max height

so delta(U) = mg[delta(y)]

how do i get the max height?