(1) In the process of carving, nanmu itself has not changed, but its shape has changed, so this is a physical change; (2) When paddling, the paddle can be regarded as a lever, but it is actually a laborious lever; (3) Because the distance between the dragon boat and the house on the shore is changing, the house on the shore moves with the rowing dragon boat as the reference; (4) According to Archimedes principle, F float = ρ water gV row =1.0×103kg/m3×10n/kg× 30m3 = 3×105n.