Question

What is critical velocity use in real life?

Answer 1

helloo!!

Critical velocity is the velocity of a liquid flow upto which its flow is streamlined and after which its flow becomes turbulent.
The critical velocity depends on coefficient of viscosity 

hope it helps

Answer 2

Critical velocity is defined as the speed at which a falling object reaches when both gravity and air resistance are equalised on the object. The other way of defining critical velocity is the speed and direction at which the fluid can flow through a conduit without becoming turbulent.