Growth is the right answer, because ecdysis or moulting term is associated with shedding of exoskeleton . Snakes do so to increase in size and for development
When you drop a ball, it is dropped DOWNWARDS so the number is represented by a negative number. If you toss the ball up it will be a positive number.
To answer your question:
When an object is dropped downwards there will be a negative number since the object is falling downwards.
