
πΉ Introduction
When a body is partly or wholly immersed in a fluid (liquid or gas), it experiences an upward force. This upward force is called upthrust or buoyant force. It acts opposite to the weight of the body and is the reason why objects feel lighter in water or why balloons rise in the air.
πΉ Definition of Upthrust
π Upthrust (or buoyant force) is the upward force exerted by a fluid on a body immersed in it.
This happens because the pressure of the fluid increases with depth, creating a greater force on the bottom surface of the object than on the top surface.
πΉ Explanation in Liquid
Consider an object immersed in water.
The pressure at the bottom of the object is greater than at the top because pressure increases with depth.
This difference in pressure produces a net upward force, which is the upthrust.
πΉ Explanation in Gas
Similar to liquids, gases also exert upthrust.
Example: A helium balloon rises in air because the upthrust of air on the balloon is greater than the weight of the balloon.
πΉ Archimedesβ Principle
The magnitude of upthrust is explained by Archimedesβ Principle:
π When a body is immersed in a fluid, it experiences an upthrust equal to the weight of the fluid displaced by the body.
Mathematically,
Fb=ΟβgβV
Where,
FbΒ = Upthrust (buoyant force)
ΟΒ = Density of fluid
g= Acceleration due to gravity
V= Volume of fluid displaced
πΉ Examples of Upthrust in Daily Life
A stone feels lighter in water than in air.
A ship floats on water due to upthrust balancing its weight.
A balloon rises in air because of upthrust by the atmosphere.
Submarines adjust their depth by controlling the upthrust through ballast tanks.
β Conclusion
Upthrust is a fundamental concept in physics that explains floating and sinking of objects in fluids. It is essential in designing ships, submarines, and even hot-air balloons.
