''WHEN AN OBJECT IS IMMERSED IN A FLUID, THE UPTHRUST ON THE OBJECT ISEQUAL TO THE WEIGHT OF THE FLUID DISPLACED.''
THE LAW OF FLOATATION
A floating object displaces its own weight of the fluid in which it floats.
The buoyancy acting on the object due to water must exactly counteract the weight of the object, i.e. the two have equal magnitude. So, a partially immersed object floats in a liquid when the buoyancy acting on it equals the weight of the object. A large ship at sea floats precisely because the weight of the seawater it displaces, i.e. buoyancy acting on the ship, equals the total weight of the ship. For a solid piece of iron, even if Buoyancy is maximized by fully immersing it in water, its weight always exceeds the Buoyancy of water. That is why it sinks in water.
An equivalent and useful criterion for flotation of any object is that it will float in a liquid, if the density of the object is less than that of the liquid. This is true, for example, for wood or ice, both of which have a lower density than water. A solid piece of iron sinks in water because the density of iron is greater than that of water. However, a thin walled, hollow ball of iron, with adequate volume of air trapped within it, floats in water. In this case, the trapped air has lowered the average density of the ball, so that it is less than that of water.
A given object may sink in one liquid, but float in another liquid. For example, a solidpiece of iron sinks in water, but it will float, partially submerged, in a pool of mercury.We can thus conclude that mercury must have a higher density than iron, which is true.
An equivalent and useful criterion for flotation of any object is that it will float in a liquid, if the density of the object is less than that of the liquid. This is true, for example, for wood or ice, both of which have a lower density than water. A solid piece of iron sinks in water because the density of iron is greater than that of water. However, a thin walled, hollow ball of iron, with adequate volume of air trapped within it, floats in water. In this case, the trapped air has lowered the average density of the ball, so that it is less than that of water.
A given object may sink in one liquid, but float in another liquid. For example, a solidpiece of iron sinks in water, but it will float, partially submerged, in a pool of mercury.We can thus conclude that mercury must have a higher density than iron, which is true.