Here's why:

* Gravity: The primary force acting on a falling object is gravity. Gravity constantly pulls the object downwards, causing it to accelerate.

* Air Resistance: As the object falls faster, it encounters more air resistance (also called drag). Air resistance opposes the motion of the object and increases as the object's speed increases.

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

In summary:

* Initially: The velocity of a falling object increases because gravity is the dominant force.

* As it falls faster: Air resistance increases, opposing the acceleration.

* Eventually: The forces balance, and the object reaches a constant velocity (terminal velocity).