Here's why:
* Terminal Velocity: Terminal velocity is the constant speed that a freely falling object eventually reaches when the force of air resistance equals the force of gravity.
* Forces in Balance: At terminal velocity, the forces acting on the object are balanced. The downward force of gravity is exactly counteracted by the upward force of air resistance.
* Newton's Second Law: Newton's Second Law of Motion states that acceleration is directly proportional to the net force acting on an object. Since the net force is zero at terminal velocity, the acceleration is also zero.
In simpler terms: Once an object reaches terminal velocity, it stops accelerating and falls at a constant speed.