Question

What is Pseudo Force and when it is applied?

Answer 1

Pseudo force is a fictitious force, that acts on all masses whose motion is described using a non-inertial frame of reference, such as a rotating reference frame.
It means when a body is accelerating and if you want to use Newton's law on that frame then you have to apply pseudo force to analyze the acceleration of that body with respect to ground.
Just remember, whenever there is a system of two bodies and they are accelerated, then if you have to apply Newtons law on each body then you have to apply pseudo force(F=ma) in the opposite direction,
where m= mass of the body on which pseudo force is applied, a= acceleration of frame