Buoyancy is one of the key principles of physics that explains the upward force that fluid, liquid or gas, exerts on an object that is partially or wholly immersed in it. It opposes the weight of the object and causes it to float, sometimes making it sink and then pop up above water.

This is the upward force exerted by the liquid.

The symbol of Buoyancy is B or FB. It is a vector quantity and has both magnitude as well as direction. The unit of buoyancy is Newton [N].

Buoyancy is caused due to the change in pressure. The pressure is higher at the bottom of the object and decreases as we move up. The bottom pressure pushes the object upward and top pressure pushes it downward. So, the net force of the object is upward. 

Formula 

Buoyant Force in terms of Pressure

Buoyant force Fb, in terms of pressure, is represented as 

Where, 

• F2 = force acting upwards 

• F1 = force acting downwards 

Force, F=PA 

Where, 

• P = Pressure and 

• A = Area 

In terms of Area Height and Volume, it is expressed as 

Where, 

• ρ is the density of the fluid is ρ

• g is the gravity

• V is the  volume of the immersed part of the body in the fluid

• h is the height of the submerged portion

• A is the area

Solved Problem

Problem: A cube with side length of 0.2 m is submerged in water. What is the buoyant force acting on it?

Solution:

Volume of the Cube: 

V=side3

=(0.2 m)3

=0.008 m3

Density of Water: ρ=1000  kg/m3

Acceleration due to Gravity: g=9.81  m/s2

Find the Buoyant Force: 

F b=ρ⋅V⋅g

​ρ=1000  kg/m3⋅0.008 m3⋅9.81  m/s2

F\ nb​ =1000 kg/m30.008 m39.81 m/s2

         = 78.48  N

The buoyant force acting on the cube would be approximately 78.48 N.

 

Other Related Sections

NCERT Solutions | Sample Papers | CBSE SYLLABUS| Calculators | Converters | Stories For Kids | Poems for kids| Learning Concepts I Practice Worksheets I Formulas | Blogs | Parent Resource