A log of wood of mass 120 kg floats in water. The weight that can be put on the raft to make it just sink should be (density of wood = 600 kg/m3)

Volume of log of wood V = massdensity = 120600                                         = 0.2 m3Let x be the weight that can be put on the log of wood.So weight of the body = (120 + x)×10NWeight of displaced liquid = Vσg = 0.2 ×103×10The body will just sink in liquid if the weight of the body will be equal to the weight of displaced liquid.(120+x)×10 = 0.2×103×10⇒ 120+x = 100         x = 80 kg