Simple Harmonic Motion of bobble toy

[Jennisa]

*note: my previous thread will be deleted because I didn't include relevant equations + I put two unrelated problems in the same thread.

1. Homework Statement
A cat bobble head doll consists of a weighted head on top of a spring. When the head hangs straight sown in equilibrium, it is observed that the spring stretches 2cm. When the head is displaced upward by 1 cm, it is observed to oscillate with a frequency of 3 Hz.

a) Find the spring constant of the bobble head
b) Find the mass of the bobble head

Homework Equations

T = 2pi square root (m/k)

The Attempt at a Solution

I tried to use the formula T = 2pi square root(m/k) to find m and k but I cannot use this because the mass and k are not given.

 

[BvU]

No, but you know that the spring stretches 2 cm under a force mg. What does that tell you about the relationship between k and m ?