Here's why:

* Gravity: When an object falls, gravity pulls it downwards, causing it to accelerate.

* Air Resistance: As an object falls faster, it encounters more air resistance (drag). This force opposes the object's motion.

* Balance: Eventually, the force of air resistance becomes equal to the force of gravity. At this point, the object stops accelerating and reaches a constant speed, called terminal velocity.

Important Note: Terminal velocity depends on factors like:

* Object's shape and size: A wider object experiences more air resistance.

* Object's mass: A heavier object has a greater gravitational force acting on it.

* Air density: Thicker air creates more resistance.