Floating and Sinking

Table of Contents

Floating and Sinking with examples

Floating – An object will float on a liquid, if its density is less than the density of the liquid.
Sinking – An object will sink in a liquid, if its density is more than the density of the liquid.

Floating

Definition – Floatation is a state of rest or movement of a lighter object on the surface of a heavier liquid.

When an object is placed over a liquid whose density is more than the density of the object, the object floats on the liquid.

Example – If a piece of wood or cork is placed over water, it floats on water because the density of water is more than the density of the cork or wooden piece. Due to this very reason, an ice cube floats when placed over a cold drink taken in a glass jar.

Sinking

Definition – Sinking is a state of rest or movement of a heavier object below the surface of a lighter liquid.

When an object is placed over a liquid whose density is less than the density of the object, the object sinks into the liquid.

Example – If a spoon or a screw of iron is placed over water, then it sinks because the density of iron (7800 kg/m³) is greater than the density of water (1000 kg/m³). Similarly, a gold ring or a glass lens will sink in water.

More examples of floating and sinking

An ice cube sinks in kerosene but floats on water because the density of the ice cube is more than the density of kerosene but less than the density of water.

An iron nail sinks in water but floats on mercury because density of iron (7800 kg/m³) is greater than the density of water (1000 kg/m) but lesser than the density of mercury (13600 kg/m²)

Due to the presence of salts, the density of seawater is more than the density of freshwater. So, it i easier to swim in seawater than in freshwater.

Applications of Floatation

The density of ice is less than the density of water. Hence, huge masses of ice, called icebergs, continue to float on water.

Density of iron is much more than the density of water. So, an iron needle sinks in water. However, an iron ship is designed in such a way that it is mostly hollow from within. Thus, the volume of iron ship becomes very large as compared to its mass and, hence, its effective density becomes less than that of water. So, a ship floats on water.

In inverter batteries, acid battery hydrometer is used to check the density of acid solution. A hydrometer works on the principle of floatation.