Basics of Archimedes Principle


We know that every object that we are surrounded by is exerting force on each other. It would be interesting to learn that even the fluids exert force when an object is immersed in it.

This force that is experienced by an object due to fluids is understood with the help of Archimedes principle.

What is the Archimedes Principle?

According to the Archimedes principle, the upward buoyant force that is exerted on an object when it is immersed in a fluid, whether partially or fully submerged, is equal to the weight of the fluid that is displaced by the object and is acted in the upward direction at the centre of the mass of the displaced fluid.

This principle was discovered by Archimedes of Syracuse of Greece. So, in simple terms, we can say that according to the Archimedes principle the weight of an object is equal to the weight of the liquid displaced by it when it is either partially or fully submerged.

What is the Archimedes Principle Formula?

The mathematical representation of the Archimedes principle is as follows:

Archimedes principle formula


  • Fb is the buoyant force
  • ⍴ is the density of the fluid
  • g is the acceleration due to gravity
  • V is the submerged volume

How was the Archimedes Principle Discovered?

There is an interesting story behind the discovery of the Archimedes principle. Years ago, there lived a king named King Hieron II in Syracuse. He was worried that the gold used in the crown was not solid, and he doubted his crown makers.

He presumed that they were using less valuable materials such as silver in place of gold. The king then asked Archimedes to help to identify if his assumption was right. It is hilarious that Archimedes came up with a way to measure the density of the material while he was taking bath.

He realized that the water displaced from the bathtub is equal to his mass. This realization made him so excited that he jumped out shouting ‘Eureka’ and ran in the streets with excitement.

Applications of Archimedes Principle

The following three are the most commonly known applications of Archimedes principle:


The submarine comes with a component known as ballast tank which is the reason behind it to be underwater always. The ballast tank allows the water to enter inside the submarine maintaining the weight of the submarine greater than the buoyant force.

This makes the submarine stay inside water intact.

Hot-air balloon

The buoyant force of the hot-air balloon is less than its surrounding air. For the balloon to descend, the buoyant force of the hot-air balloon is increased. This is achieved by varying the quantity of hot air in the balloon. 


The relative density of liquids is measured using an instrument called a hydrometer. The hydrometer consists of lead shots that make them float vertically in the liquid. As the hydrometer sinks, the lesser will be the density of the liquid.

It is important to understand that the buoyant force is different from specific gravity. The buoyant force is caused due to the difference in pressure that is acting on the opposite side of an object when it is immersed in the liquid. While specific gravity is the ratio between the density of an object and the reference object.

Learn more about specific gravity and related terms at BYJU’S.

Click Here

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button