• Buoyancy

When a body is immersed in a fluid (liquid or gas) it exerts an upward force on the body. This upward force is called up thrust or buoyant force (B or FB) and the phenomenon is termed as buoyancy.

It is a common experience that when a piece of cork is placed in water it floats with two-fifth of its volume inside water. If the cork piece is pushed into water and released it comes to the surface. Buoyant force acts in upward direction and it depends on the density of the fluid. Buoyant force is a vector quantity as it has both magnitude and direction. It acts upward & the SI unit is the Newton [N].

If force of gravitational attraction of the earth on the surface of the object is less than the buoyant force exerted by fluid on the surface of the object then the object floats.

If force of gravitational attraction of the earth on the surface of the object is more than the buoyant force exerted by fluid on the surface of the object then the object sinks. That is why, alpine sinks and boat/ship floats on the surface of water (Archimedes’ principle).