When an object falls through a fluid medium, such as air, it experiences two main forces: gravity pulling it downward and air resistance pushing against it in the opposite direction. Initially, when the object starts to fall, the force of gravity is greater than the air resistance, causing the object to accelerate.
As the object accelerates, the air resistance also increases. Eventually, a point is reached where the force of air resistance becomes equal to the force of gravity acting on the object. At this point, the object stops accelerating and reaches a constant velocity called terminal velocity.
Once an object reaches terminal velocity, the forces acting on it balance out. The force of gravity pulling it downward is countered by the upward force of air resistance. Since the forces are equal in magnitude and opposite in direction, the net force on the object becomes zero. As a result, the object no longer accelerates and continues to fall at a constant speed.
It's important to note that terminal velocity differs for different objects based on factors such as their size, shape, and mass. Objects with a larger surface area or greater air resistance will reach terminal velocity at a lower speed compared to objects with smaller surface area or lower air resistance. For example, a feather has a lower terminal velocity than a stone due to the significant difference in their air resistance.
In summary, objects continue to fall after attaining terminal velocity because the opposing forces of gravity and air resistance balance each other, resulting in a constant velocity rather than further acceleration.