A group of boys went for boating as a picnic. They were dancing and singing. Suddenly, their boat lost its balance and the boys fell into the river. By seeing this, many fishermen rushed for their help and provided them pieces of wood so that they could float and save themselves. The alertness of the fishermen saved the life of all the boys. a) What would be the density of water if the boys saved themselves with a wood that floats with 1/4th of its volume above the water surface? b) What is the use of life saving jackets while going on a boat?
a) Here, Volume of wood body outside water = V/4 Volume of wood body inside water = V V - 4 Now, weight of water displaced by wood = 3V 3 x 10 g 4 Therefore, Vρg = 3V 3 x 10 g 4 Then, ρ = 750 kg/m3 b) This is because the lives saving jackets have air in them which keeps us afloat if we accidently fall into water.
