Question

what is fictious force and how centrifugal force is a fictitious force

Answer 1

A fictitious force is a apparent force that acts on all masses whose motion is described using a non- inertial frame of reference, such as rotating reference frame.

The same situation occurs with circular motion where the acceleration is due to a constant change in direction so that a mass rotating in a circle has an acceleration toward the center.The centrifugal force is the inertial force which acts away from the center.

Hope this help you

Answer 2

Let's assume that you are driving a truck with constant velocity (same speed and same direction).  Next to you on the truck seat/bench is a basketball. While you are buckled in, the basketball is not.  As you and the truck approach an intersection, you decide to make a left turn. As you make the left turn, the basketball on the truck bench begins to roll to the right, away from you, towards the passenger door.