Question

what what is inertia concept of inertia and reference of motion

Answer 1

This includes changes to the object's speed, direction, or state of rest. ... The term "inertia" is more properly understood as shorthand for "the principle of inertia" as described by Newton in his First Law of Motion: an object not subject to any net external force moves at a constant velocity.

Inertia - Wikipedia

Answer 2

INERTIA

Inertia is the natural tendency of objects to resist a change in their state of rest or of uniform motion.

                      OR

Inertia is the natural tendency of undisturbed objects to stay at rest or keep moving with constant velocity.

INERTIA OF REST

It is the natural tendency of an object by which the object and to remain at the state of rest.

For example:-  If you are in a bus which is at rest and when the bus suddenly starts then our leg which is in contact with the bus will move along with the bus but our upper body part will tend to remain at the state of rest that's why we lean backward when the bus suddenly starts.

INERTIA OF MOTION

it is the natural tendency of an object to remain at the state of moving with a uniform velocity.

For example :- When we are in a moving bus then our whole body is at motion but when the bus suddenly stops then our leg which is in contact with the bus stops but upper part of our body tends to remain at the state of motion with uniform velocity so we lean forward when a bus suddenly stops.

INERTIA OF DIRECTION

It is the natural tendency of an object to remain at the state of motion at that direction in which it is moving.

For example :- When we are in a moving bus and the bus suddenly turns towards right then we will find that our body is leaning towards left it is because the leg which is in contact of bus move along with the bus in right direction but our upper body part tends to remain at that direction that's why we lean leftward.