leprofece said:
maybe w= 2pi/t
w= 6,28/0,3
I tried (2pi)sqrt(L/g) solve to L But I don't get the 0.022 m that is the book answer
I'm afraid that is the formula for a pendulum with length L.
The formula for a mass on a spring is
$$\omega = \sqrt{\frac K m}$$
For this problem we won't need it though.
It appears you have more information than you need.
it could be get the aceleration to get the force
to try f = Kx
Good!
Let's pick $y$ for the coordinate though, to emphasize it's a vertical coordinate.
So we have an elastic force $F_e$:
$$F_e = Ky$$
And we also have the force of gravity.
$$F_G = mg$$
When the mass is at rest, the elastic force and the force of gravity have to be equal and opposite.
That is:
$$F_e = F_G$$
$$Ky = mg$$
Now if we remove the mass from the spring, the spring will return to its neutral position at $y=0$.
What can you conclude then about the $y$ where the mass was at rest before?