I have found a question that has got to my nerves : A block of wood of length 40 cm and area of cross-section 15 cm2 floats in water with 3/8 of it's length above water. What is the density of wood ? (Density of water - 1g/cm3). My attempt to get the solution : Length of wood above water = 3/8 * 40 = 15cm Length of wood below water = (40-15)cm = 25cm Now, Upthrust = 375cm3*1*10 = 3750 N Rest, I don't know ! Please help. It's urgent because I am going to face some deadly questions the day after tomorrow. Thank You.