Here's why:
* Gravity's pull: Initially, the object accelerates downwards due to gravity.
* Air resistance increases: As the object speeds up, the force of air resistance (also called drag) increases. Air resistance acts in the opposite direction to the object's motion.
* Terminal velocity: Eventually, the force of air resistance becomes equal in magnitude to the force of gravity. At this point, the net force on the object is zero, and it stops accelerating. The object continues to fall at a constant velocity, known as terminal velocity.
Key Points:
* Terminal velocity depends on the object's shape, size, and mass, as well as the density of the air.
* A more streamlined object will have a higher terminal velocity than a less streamlined object of the same mass.
* A heavier object will have a higher terminal velocity than a lighter object of the same shape and size.
Example:
Imagine a skydiver jumping out of a plane. Initially, they accelerate downwards due to gravity. As they speed up, air resistance increases. Eventually, they reach terminal velocity, which is typically around 120 mph. At this point, they no longer accelerate and continue falling at a constant speed.
