G=mg=3kg× 10N/kg=30N，

∵ Wood blocks float,

Buoyancy of wood blocks:

F float = g = G = 30N；

(2)∫F float = ρ water v row g,

∴v immersion =v row = F floating ρ water G = 30n/kloc-0 /×103kg/m3×10n/kg = 3x10-3m3,

Such as the title, v immersion = 3 5 v wood,

∴v wood = 5 3 volts immersion = 53× 3×10-3m3 = 5×10-3m3.

Answer: (1) The buoyancy of the block at rest is 30N；;

(2) The volume of wood block is 5× 10-3m3.