let's understand about Archimedes Principle

we all aware the fact that some objects float in water While others sink.

let's look at the balloon. Do you know what makes a balloon float on water? 

Well, it's the upward force exerted by water that makes the balloon float, to experience this try pushing the balloon under water you will feel an upward force that makes it difficult to push the balloon down, now release the balloon. It bounces back to the surface. 

What happens here? Is that the applied force acts in the downward Direction pushing the balloon down? But the water exerts an upward force on the balloon pushing it up. This upward force exerted by water in the balloon is known as up thrust or buoyancy and the upward force is called the buoyant force. 

Have you ever wondered why an iron nail sinks while a huge giant ship floats on water. 

Let's see, the iron nail sinks as it is solid and compact with less volume in water and its density is greater than water.

Thus the upthrust is exerted by water on the nail is less than the weight of the nail. This causes it to sink and iron ship floats as it is hollow shells were there and occupies more volume in water and its density is less than water. Does the up thrust exerted by water on the ship is greater than the weight of the ship letting it float these examples indicate that the magnitude of the buoyant force depends on the Volume = v of the immersed part of the body the density = rho of the fluid and the axial Direction due to gravity G thus up thrust of buoyant force is equal to v rho G. In general object experiences a loss of weight in water due to the upthrust and it is equal to the weight of water displaced by it. This is better answered using the law of buoyancy also known as Archimedes Principle. Named after the Greek scientist who discovered it.

Archimedes Principle states that when an object is immersed in a liquid the apparent loss of weight of an object is equal to the up trust and this is also equal to the weight of the liquid displaced .

we see the use of this principle in our daily lives. Ever caught a fish with a fishing line when pulling the line you would have felt the weight of the fish in water is lighter than when the fish has surfaced.

see the weight of the fish in water is four kilos. It's approximate wait outside would be 5 kilos. Well, the water level to has come down this difference in the volume of water level will equal the loss in weight of the fish when in water, that is the weight of the fish outside - its weight when immersed in water equals a loss in weight of the fish. 

5kg - 4kg = 1kg

So the loss of weight of the fish will equal the weight of the decreased water. This is because upthrust of buoyant force is equal to the weight of the decreased amount of water does Archimedes principle is verified.

Certain Technologies today work based on the archimedies principle. To name a few, the designing of ships and submarines hydrometer is used to find the specific gravity of liquid and lacto meters used to determine purity of milk.

Things to remember 

•  The upward force exerted by a fluid is called a Thrust of buoyant force. 
• Up trust of buoyant force = V Ro G.
• Archimedes principle states that "when a body is partially or fully immersed in a fluid it experiences an upward force that is equal to the weight of the fluid displaced by it.
• Archimedes principle is also known as a law of buoyancy.