Answer:

Step-by-step explanation:
As the buoyant force is proportional to the length of which the wood is submerged in water, we can model the buoyant force as a spring force and the bobbing wood is a simple harmonic motion described as A cos (ωt + φ) where

where k (N/m) is the "spring" buoyant constant and m is the mass of wood
The buoyant force is basically the weight of water displaced by the submerged wood, which is the gravity acting on the cylindrical volume

Since the cylindrical has a form of AL where A is the base area and L is the length submerged

As L can be treated as the spring "stretched/compressed" length, the rest is k:


Therefore
