An object is in motion when it undergoes a continuous change of what?

continuous change in position with respect to time

Explanation:
Velocity is defined as the rate of change of the position of an object with respect to its time.
It's the vector quantity of speed as it has both magnitude and direction.

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Ok what do you need with

Two cars collide, lock bumpers and move together after the collision.this collision is known as perfectly inelastic collision.