Solve Jumping Toy Problem: Find Spring Constant & Power

[MozAngeles]

Homework Statement

A spring is compressed 1.5 cm and propels a 49g toy to a height of 45 cm.
a. Find the spring constant
b. The average power of the spring during propulsion.
c. The instantaneous power exerted when the compression is just .75cm

Homework Equations

k=F/\Deltax
Power=Work/time

The Attempt at a Solution

i thought the spring constant ,k, would be (mass of toy x 9.81)/(.015), but this is wrong.
then work would be, force(which i don't know how to find) x distance(.45).. but I am not sure

 

[Kikora]

Try Using this:

Elastic potential energy stored in wire or spring (Amount of work stored)

* W = ½k_effX², where X is the extension of spring

 

[MozAngeles]

Okay, but I'm still not sure how to find the spring constant, was I on the right track by using F/\Deltax, where x=.015 m

 

[MozAngeles]

and force is equal to .049x9.81

 

[MozAngeles]

Okay so i figured out the constant by conservation of energy.
1/2kx²=mgh, solve for k
then for power p=w/t, i find t by finding\omega=sqrt. (k/m) then using that to find T, the period.
then work= 1/2kx², so then i just divide the w/T, would this be correct?