Hello students, we are going to learn the important characteristics of fluid known as buoyancy. While jumping into water in a swimming pool we felt that our velocity by which we jumped in decreases and gets little lighter. Look at the following diagram in which water is stored in vessel. Now, if we make a small hole on a vessel at the point shown in fig.
We will observe the water immediately starts flowing through the hole made on the vessel. This indicates that the molecules of water exert the force on the wall of vessel. This force acts perpendicular to the given point on the vessel.
The force exerted by fluid on the wall of vessels acts perpendicular to the given point is known as buoyant force and the property of liquid is known as buoyancy.
It acts opposite of applied force. Refer the following fig. in which a stone is falling in container having water in influence of gravitational force; the motion of stone is abstracted by water surface due to buoyancy. The reaction this can be easily experienced by the spilling out of water from the container.
Magnitude of buoyant force decides whether the object is going to float or sink on the surface of liquid.
When the magnitude of buoyant force exerted by liquid is greater than that of downward force (weight) of object, it will float.
When the magnitude of buoyant force exerted by liquid is less than that of the downward force (weight) of object, it will sink in liquid surface.
When the magnitude of buoyant force exerted by liquid is equal to that of the downward force (weight) of object, it will float inside liquid surface.
Magnitude of the buoyant force was given by Sir Archimedes.
Uses of buoyant force:
- A person can swim easily on free surface of water is due to the buoyant force exerted by water, which reduces the effective weight of person so that it can float on water surface.
- Heavy ships or boats can easily floats on the river/ocean surface due tremendous buoyant force exerted by ocean surface due to its large volume.