CBSE Class 9 Answered
Iron nail sinks in water because the density of iron is more than the density of water. Hence the weight of the nail is comparatively greater than the upthrust that acts on water.
Ships are made of iron yet they do not sink as ships are hollow and the empty space in it contains air making the average density lesser than that of water. Consequently, even with a smaller portion of ship immersed in water, the weight of water displaced by the immersed part of the ship becomes equivalent to the net weight of the ship causing it to float.