what is inertia
Newton’s first law of motion states that an object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied force.
In other words, all objects resist a change in their state of rest or motion.
In a qualitative way, the tendency of undisturbed objects to stay at rest or to keep moving with the same velocity is called inertia.
We tend to remain at rest with respect to the seat until the driver applies a braking force to stop the motorcar due to the inertia of motion.